[2/2] gdb/testsuite: tests for debug lookup within the sysroot

  Add tests for looking up debug information within the sysroot via both
build-id and gnu_debuglink.

I wanted to ensure that the gnu_debuglink test couldn't make use of
build-ids, so I added the 'no-build-id' flag to gdb_compile.

As these tests rely on setting the sysroot, if I'm running a
dynamically linked executable, GDB will try to find all shared
libraries within the sysroot.  This would mean I'd have to figure out
and copy all shared libraries the executable uses, certainly possible,
but a bit of a pain.

So instead, I've just compiled the test executable as a static binary.
Now there are no shared library dependencies.

I can now split the debug information out from the test binary, and
place it within the sysroot.  When GDB is started and the executable
loaded, we can check that GDB is finding the debug information within
the sysroot.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30871
---
 gdb/testsuite/gdb.base/sysroot-debug-lookup.c |  22 +++
 .../gdb.base/sysroot-debug-lookup.exp         | 162 ++++++++++++++++++
 gdb/testsuite/lib/gdb.exp                     |  13 ++
 3 files changed, 197 insertions(+)
 create mode 100644 gdb/testsuite/gdb.base/sysroot-debug-lookup.c
 create mode 100644 gdb/testsuite/gdb.base/sysroot-debug-lookup.exp
  

On 5/20/24 16:14, Andrew Burgess wrote:
> Add tests for looking up debug information within the sysroot via both
> build-id and gnu_debuglink.
> 
> I wanted to ensure that the gnu_debuglink test couldn't make use of
> build-ids, so I added the 'no-build-id' flag to gdb_compile.
> 
> As these tests rely on setting the sysroot, if I'm running a
> dynamically linked executable, GDB will try to find all shared
> libraries within the sysroot.  This would mean I'd have to figure out
> and copy all shared libraries the executable uses, certainly possible,
> but a bit of a pain.
> 
> So instead, I've just compiled the test executable as a static binary.
> Now there are no shared library dependencies.
> 

Make sense.

> I can now split the debug information out from the test binary, and
> place it within the sysroot.  When GDB is started and the executable
> loaded, we can check that GDB is finding the debug information within
> the sysroot.
> 
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30871
> ---
>   gdb/testsuite/gdb.base/sysroot-debug-lookup.c |  22 +++
>   .../gdb.base/sysroot-debug-lookup.exp         | 162 ++++++++++++++++++
>   gdb/testsuite/lib/gdb.exp                     |  13 ++
>   3 files changed, 197 insertions(+)
>   create mode 100644 gdb/testsuite/gdb.base/sysroot-debug-lookup.c
>   create mode 100644 gdb/testsuite/gdb.base/sysroot-debug-lookup.exp
> 
> diff --git a/gdb/testsuite/gdb.base/sysroot-debug-lookup.c b/gdb/testsuite/gdb.base/sysroot-debug-lookup.c
> new file mode 100644
> index 00000000000..e67331d3150
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/sysroot-debug-lookup.c
> @@ -0,0 +1,22 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   Copyright 1992-2024 Free Software Foundation, Inc.
> +
> +   This program is free software; you can redistribute it and/or modify
> +   it under the terms of the GNU General Public License as published by
> +   the Free Software Foundation; either version 3 of the License, or
> +   (at your option) any later version.
> +
> +   This program is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +   GNU General Public License for more details.
> +
> +   You should have received a copy of the GNU General Public License
> +   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
> +
> +int
> +main ()
> +{
> +  return 0;
> +}
> diff --git a/gdb/testsuite/gdb.base/sysroot-debug-lookup.exp b/gdb/testsuite/gdb.base/sysroot-debug-lookup.exp
> new file mode 100644
> index 00000000000..e0377df0fa7
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/sysroot-debug-lookup.exp
> @@ -0,0 +1,162 @@
> +# Copyright 2024 Free Software Foundation, Inc.
> +#
> +# This program is free software; you can redistribute it and/or modify
> +# it under the terms of the GNU General Public License as published by
> +# the Free Software Foundation; either version 3 of the License, or
> +# (at your option) any later version.
> +#
> +# This program is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +# GNU General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
> +
> +# Test GDB's ability to find debug information by looking within the
> +# sysroot.
> +#
> +# We compile a static binary (to reduce what we need to copy into the
> +# sysroot), split the debug information from the binary, and setup a
> +# sysroot.
> +#
> +# The debug-file-directory is set to just '/debug', but we're
> +# expecting GDB to actually look in '$SYSROOT/debug'.
> +#
> +# There's a test for using .build-id based lookup, and a test for
> +# gnu_debuglink based lookup.
> +
> +require {!is_remote host}
> +
> +standard_testfile

Consider using "standard_testfile main.c" and dropping 
gdb/testsuite/gdb.base/sysroot-debug-lookup.c.

> +
> +# Create a copy of BINFILE, split out the debug information, and then
> +# setup a sysroot.  Hide (by moving) the actual debug information file
> +# and create a symlink to the hidden debug information from within the
> +# sysroot.
> +#
> +# Start GDB, set the sysroot, and then load the executable, ensure GDB
> +# finds the debug information, which must have happened by lookin in
> +# the sysroot.
> +proc_with_prefix lookup_via_build_id {} {
> +    set filename ${::binfile}_1
> +    if { [build_executable "build exec" ${filename} $::srcfile \
> +	      {additional_flags=-static debug build-id}] } {
> +	return
> +    }
> +
> +    # Split debug information into a .debug file, remove debug
> +    # information from FILENAME.  Don't add a .gnu_debuglink to
> +    # FILENAME, we rely on the build-id.
> +    if {[gdb_gnu_strip_debug $filename { no-debuglink }] != 0} {
> +	unsupported "cannot split debug information from executable"
> +	return
> +    }
> +
> +    set sysroot [standard_output_file "sysroot1"]
> +    set debug_dir "/debug"
> +
> +    set debug_symlink \
> +	$sysroot/$debug_dir/[build_id_debug_filename_get $filename]
> +
> +    set build_id_dir [file dirname $debug_symlink]
> +
> +    set debug_filename ${filename}_hidden_debug
> +
> +    remote_exec build "mkdir -p $build_id_dir"
> +    remote_exec build "mv $filename.debug $debug_filename"
> +    remote_exec build "ln -sf $debug_filename $debug_symlink"
> +
> +    clean_restart
> +
> +    gdb_test_no_output "set sysroot $sysroot" "set sysroot"
> +    gdb_test_no_output "set debug-file-directory $debug_dir"
> +
> +    gdb_file_cmd $filename
> +
> +    gdb_assert { $::gdb_file_cmd_debug_info eq "debug" }
> +
> +    set re [string_to_regexp "Reading symbols from $debug_filename..."]
> +    gdb_assert {[regexp $re $::gdb_file_cmd_msg]}

Consider adding a friendlier test name, likewise in the other proc.

Currently we get for a fail the not very meaningful:
...
FAIL: $exp: lookup_via_build_id: [regexp $re $::gdb_file_cmd_msg]
...

> +}
> +
> +# Create a copy of BINFILE, split out the debug information, and then
> +# setup a sysroot.  Hide (by moving) the actual debug information file
> +# and create a symlink to the hidden debug information from within the
> +# sysroot.
> +#
> +# Copy the executable into the sysroot and then start GDB, set the
> +# sysroot, and load the executable.  Check that GDB finds the debug
> +# information, which must have happened by lookin in the sysroot.
> +proc_with_prefix lookup_via_debuglink {} {
> +    set filename ${::binfile}_2
> +    if { [build_executable "build exec" ${filename} $::srcfile \
> +	      {additional_flags=-static debug no-build-id}] } {
> +	return
> +    }
> +
> +    # Split debug information into a .debug file, remove debug
> +    # information from FILENAME.
> +    if {[gdb_gnu_strip_debug $filename] != 0} {
> +	unsupported "cannot split debug information from executable"
> +	return
> +    }
> +
> +    # We're going to setup the sysroot like this:
> +    #
> +    # sysroot2/
> +    #    bin/
> +    #      $FILENAME
> +    #    debug/
> +    #      bin/
> +    #        $FILENAME.debug
> +    #
> +    # When looking up debug information via the debuglink, GDB will
> +    # only search in the sysroot if the original objfile was in the
> +    # sysroot.  And GDB will resolve symlinks, so if the objfile is
> +    # symlinked to outside the sysroot, GDB will not search in the
> +    # sysroot for the debug information.
> +    #
> +    # So we have to copy the executable into the sysroot.
> +    #
> +    # We are OK to symlink the debug information to a file outside the
> +    # sysroot though.
> +
> +    set sysroot [standard_output_file "sysroot2"]
> +
> +    foreach path { bin debug/bin } {
> +	remote_exec build "mkdir -p $sysroot/$path"
> +    }
> +
> +    # Copy the executable into the sysroot.
> +    set file_basename [file tail $filename]
> +    set exec_in_sysroot ${sysroot}/bin/${file_basename}
> +    remote_exec build "cp $filename $exec_in_sysroot"
> +
> +    # Rename the debug file outside of the sysroot, this should stop
> +    # GDB finding this file "by accident".
> +    set debug_filename ${filename}_hidden_debug
> +    remote_exec build "mv $filename.debug $debug_filename"
> +
> +    # Symlink the debug information into the sysroot.
> +    set debug_symlink \
> +	${sysroot}/debug/bin/${file_basename}.debug
> +    remote_exec build "ln -sf $debug_filename $debug_symlink"
> +
> +    # Restart GDB and setup the sysroot and debug directory.
> +    clean_restart
> +    gdb_test_no_output "set sysroot $sysroot" "set sysroot"
> +    gdb_test_no_output "set debug-file-directory /debug"
> +
> +    # Load the executable, we expect GDB to find the debug information
> +    # in the sysroot.
> +    gdb_file_cmd $exec_in_sysroot
> +
> +    gdb_assert { $::gdb_file_cmd_debug_info eq "debug" }
> +
> +    set re [string_to_regexp "Reading symbols from $debug_symlink..."]
> +    gdb_assert {[regexp $re $::gdb_file_cmd_msg]}
> +}
> +
> +lookup_via_build_id
> +lookup_via_debuglink
> diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
> index a63c13f9cbc..a8e8b69d6ef 100644
> --- a/gdb/testsuite/lib/gdb.exp
> +++ b/gdb/testsuite/lib/gdb.exp
> @@ -5211,6 +5211,7 @@ proc quote_for_host { args } {
>   #     debug information
>   #   - text_segment=addr: Tell the linker to place the text segment at ADDR.
>   #   - build-id: Ensure the final binary includes a build-id.
> +#   - no-build-id: Ensure the final binary does not include a build-id.
>   #   - column-info/no-column-info: Enable/Disable generation of column table
>   #     information.
>   #
> @@ -5316,6 +5317,18 @@ proc gdb_compile {source dest type options} {
>   	lappend new_options "additional_flags=-Wl,--build-id"
>       }
>   
> +    # If the 'no-build-id' option is used then disable the build-id.
> +    if {[lsearch -exact $options no-build-id] > 0} {
> +	lappend new_options "additional_flags=-Wl,--build-id=none"
> +    }
> +
> +    # Sanity check.  If both 'build-id' and 'no-build-id' are used
> +    # then what is expected from us!
> +    if {[lsearch -exact $options build-id] > 0
> +	&& [lsearch -exact $options no-build-id] > 0} {
> +	error "cannot use build-id and no-build-id options"
> +    }
> +
>       # Treating .c input files as C++ is deprecated in Clang, so
>       # explicitly force C++ language.
>       if { !$getting_compiler_info


I've added the target: prefix for the set sysroot commands, and ran into 
these three fails:
...
FAIL: gdb.base/sysroot-debug-lookup.exp: lookup_via_build_id: [regexp 
$re $::gdb_file_cmd_msg]
FAIL: gdb.base/sysroot-debug-lookup.exp: lookup_via_debuglink: 
$::gdb_file_cmd_debug_info eq "debug"
FAIL: gdb.base/sysroot-debug-lookup.exp: lookup_via_debuglink: [regexp 
$re $::gdb_file_cmd_msg]
...

The first one is just due to gdb mentioning an unresolved symlink.

But I think the next one reproduces PR30866.  So, IWBN to add this 
dimension to the test-case and add a kfail.

Anyway, as is, LGTM.

Approved-By: Tom de Vries <tdevries@suse.de>

Thanks,
- Tom
  

Tom de Vries <tdevries@suse.de> writes:

> On 5/20/24 16:14, Andrew Burgess wrote:
>> Add tests for looking up debug information within the sysroot via both
>> build-id and gnu_debuglink.
>> 
>> I wanted to ensure that the gnu_debuglink test couldn't make use of
>> build-ids, so I added the 'no-build-id' flag to gdb_compile.
>> 
>> As these tests rely on setting the sysroot, if I'm running a
>> dynamically linked executable, GDB will try to find all shared
>> libraries within the sysroot.  This would mean I'd have to figure out
>> and copy all shared libraries the executable uses, certainly possible,
>> but a bit of a pain.
>> 
>> So instead, I've just compiled the test executable as a static binary.
>> Now there are no shared library dependencies.
>> 
>
> Make sense.
>
>> I can now split the debug information out from the test binary, and
>> place it within the sysroot.  When GDB is started and the executable
>> loaded, we can check that GDB is finding the debug information within
>> the sysroot.
>> 
>> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30871
>> ---
>>   gdb/testsuite/gdb.base/sysroot-debug-lookup.c |  22 +++
>>   .../gdb.base/sysroot-debug-lookup.exp         | 162 ++++++++++++++++++
>>   gdb/testsuite/lib/gdb.exp                     |  13 ++
>>   3 files changed, 197 insertions(+)
>>   create mode 100644 gdb/testsuite/gdb.base/sysroot-debug-lookup.c
>>   create mode 100644 gdb/testsuite/gdb.base/sysroot-debug-lookup.exp
>> 
>> diff --git a/gdb/testsuite/gdb.base/sysroot-debug-lookup.c b/gdb/testsuite/gdb.base/sysroot-debug-lookup.c
>> new file mode 100644
>> index 00000000000..e67331d3150
>> --- /dev/null
>> +++ b/gdb/testsuite/gdb.base/sysroot-debug-lookup.c
>> @@ -0,0 +1,22 @@
>> +/* This testcase is part of GDB, the GNU debugger.
>> +
>> +   Copyright 1992-2024 Free Software Foundation, Inc.
>> +
>> +   This program is free software; you can redistribute it and/or modify
>> +   it under the terms of the GNU General Public License as published by
>> +   the Free Software Foundation; either version 3 of the License, or
>> +   (at your option) any later version.
>> +
>> +   This program is distributed in the hope that it will be useful,
>> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
>> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> +   GNU General Public License for more details.
>> +
>> +   You should have received a copy of the GNU General Public License
>> +   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
>> +
>> +int
>> +main ()
>> +{
>> +  return 0;
>> +}
>> diff --git a/gdb/testsuite/gdb.base/sysroot-debug-lookup.exp b/gdb/testsuite/gdb.base/sysroot-debug-lookup.exp
>> new file mode 100644
>> index 00000000000..e0377df0fa7
>> --- /dev/null
>> +++ b/gdb/testsuite/gdb.base/sysroot-debug-lookup.exp
>> @@ -0,0 +1,162 @@
>> +# Copyright 2024 Free Software Foundation, Inc.
>> +#
>> +# This program is free software; you can redistribute it and/or modify
>> +# it under the terms of the GNU General Public License as published by
>> +# the Free Software Foundation; either version 3 of the License, or
>> +# (at your option) any later version.
>> +#
>> +# This program is distributed in the hope that it will be useful,
>> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
>> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> +# GNU General Public License for more details.
>> +#
>> +# You should have received a copy of the GNU General Public License
>> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
>> +
>> +# Test GDB's ability to find debug information by looking within the
>> +# sysroot.
>> +#
>> +# We compile a static binary (to reduce what we need to copy into the
>> +# sysroot), split the debug information from the binary, and setup a
>> +# sysroot.
>> +#
>> +# The debug-file-directory is set to just '/debug', but we're
>> +# expecting GDB to actually look in '$SYSROOT/debug'.
>> +#
>> +# There's a test for using .build-id based lookup, and a test for
>> +# gnu_debuglink based lookup.
>> +
>> +require {!is_remote host}
>> +
>> +standard_testfile
>
> Consider using "standard_testfile main.c" and dropping 
> gdb/testsuite/gdb.base/sysroot-debug-lookup.c.

Done.

>
>> +
>> +# Create a copy of BINFILE, split out the debug information, and then
>> +# setup a sysroot.  Hide (by moving) the actual debug information file
>> +# and create a symlink to the hidden debug information from within the
>> +# sysroot.
>> +#
>> +# Start GDB, set the sysroot, and then load the executable, ensure GDB
>> +# finds the debug information, which must have happened by lookin in
>> +# the sysroot.
>> +proc_with_prefix lookup_via_build_id {} {
>> +    set filename ${::binfile}_1
>> +    if { [build_executable "build exec" ${filename} $::srcfile \
>> +	      {additional_flags=-static debug build-id}] } {
>> +	return
>> +    }
>> +
>> +    # Split debug information into a .debug file, remove debug
>> +    # information from FILENAME.  Don't add a .gnu_debuglink to
>> +    # FILENAME, we rely on the build-id.
>> +    if {[gdb_gnu_strip_debug $filename { no-debuglink }] != 0} {
>> +	unsupported "cannot split debug information from executable"
>> +	return
>> +    }
>> +
>> +    set sysroot [standard_output_file "sysroot1"]
>> +    set debug_dir "/debug"
>> +
>> +    set debug_symlink \
>> +	$sysroot/$debug_dir/[build_id_debug_filename_get $filename]
>> +
>> +    set build_id_dir [file dirname $debug_symlink]
>> +
>> +    set debug_filename ${filename}_hidden_debug
>> +
>> +    remote_exec build "mkdir -p $build_id_dir"
>> +    remote_exec build "mv $filename.debug $debug_filename"
>> +    remote_exec build "ln -sf $debug_filename $debug_symlink"
>> +
>> +    clean_restart
>> +
>> +    gdb_test_no_output "set sysroot $sysroot" "set sysroot"
>> +    gdb_test_no_output "set debug-file-directory $debug_dir"
>> +
>> +    gdb_file_cmd $filename
>> +
>> +    gdb_assert { $::gdb_file_cmd_debug_info eq "debug" }
>> +
>> +    set re [string_to_regexp "Reading symbols from $debug_filename..."]
>> +    gdb_assert {[regexp $re $::gdb_file_cmd_msg]}
>
> Consider adding a friendlier test name, likewise in the other proc.
>
> Currently we get for a fail the not very meaningful:
> ...
> FAIL: $exp: lookup_via_build_id: [regexp $re $::gdb_file_cmd_msg]

Done (I think).

> ...
>
>> +}
>> +
>> +# Create a copy of BINFILE, split out the debug information, and then
>> +# setup a sysroot.  Hide (by moving) the actual debug information file
>> +# and create a symlink to the hidden debug information from within the
>> +# sysroot.
>> +#
>> +# Copy the executable into the sysroot and then start GDB, set the
>> +# sysroot, and load the executable.  Check that GDB finds the debug
>> +# information, which must have happened by lookin in the sysroot.
>> +proc_with_prefix lookup_via_debuglink {} {
>> +    set filename ${::binfile}_2
>> +    if { [build_executable "build exec" ${filename} $::srcfile \
>> +	      {additional_flags=-static debug no-build-id}] } {
>> +	return
>> +    }
>> +
>> +    # Split debug information into a .debug file, remove debug
>> +    # information from FILENAME.
>> +    if {[gdb_gnu_strip_debug $filename] != 0} {
>> +	unsupported "cannot split debug information from executable"
>> +	return
>> +    }
>> +
>> +    # We're going to setup the sysroot like this:
>> +    #
>> +    # sysroot2/
>> +    #    bin/
>> +    #      $FILENAME
>> +    #    debug/
>> +    #      bin/
>> +    #        $FILENAME.debug
>> +    #
>> +    # When looking up debug information via the debuglink, GDB will
>> +    # only search in the sysroot if the original objfile was in the
>> +    # sysroot.  And GDB will resolve symlinks, so if the objfile is
>> +    # symlinked to outside the sysroot, GDB will not search in the
>> +    # sysroot for the debug information.
>> +    #
>> +    # So we have to copy the executable into the sysroot.
>> +    #
>> +    # We are OK to symlink the debug information to a file outside the
>> +    # sysroot though.
>> +
>> +    set sysroot [standard_output_file "sysroot2"]
>> +
>> +    foreach path { bin debug/bin } {
>> +	remote_exec build "mkdir -p $sysroot/$path"
>> +    }
>> +
>> +    # Copy the executable into the sysroot.
>> +    set file_basename [file tail $filename]
>> +    set exec_in_sysroot ${sysroot}/bin/${file_basename}
>> +    remote_exec build "cp $filename $exec_in_sysroot"
>> +
>> +    # Rename the debug file outside of the sysroot, this should stop
>> +    # GDB finding this file "by accident".
>> +    set debug_filename ${filename}_hidden_debug
>> +    remote_exec build "mv $filename.debug $debug_filename"
>> +
>> +    # Symlink the debug information into the sysroot.
>> +    set debug_symlink \
>> +	${sysroot}/debug/bin/${file_basename}.debug
>> +    remote_exec build "ln -sf $debug_filename $debug_symlink"
>> +
>> +    # Restart GDB and setup the sysroot and debug directory.
>> +    clean_restart
>> +    gdb_test_no_output "set sysroot $sysroot" "set sysroot"
>> +    gdb_test_no_output "set debug-file-directory /debug"
>> +
>> +    # Load the executable, we expect GDB to find the debug information
>> +    # in the sysroot.
>> +    gdb_file_cmd $exec_in_sysroot
>> +
>> +    gdb_assert { $::gdb_file_cmd_debug_info eq "debug" }
>> +
>> +    set re [string_to_regexp "Reading symbols from $debug_symlink..."]
>> +    gdb_assert {[regexp $re $::gdb_file_cmd_msg]}
>> +}
>> +
>> +lookup_via_build_id
>> +lookup_via_debuglink
>> diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
>> index a63c13f9cbc..a8e8b69d6ef 100644
>> --- a/gdb/testsuite/lib/gdb.exp
>> +++ b/gdb/testsuite/lib/gdb.exp
>> @@ -5211,6 +5211,7 @@ proc quote_for_host { args } {
>>   #     debug information
>>   #   - text_segment=addr: Tell the linker to place the text segment at ADDR.
>>   #   - build-id: Ensure the final binary includes a build-id.
>> +#   - no-build-id: Ensure the final binary does not include a build-id.
>>   #   - column-info/no-column-info: Enable/Disable generation of column table
>>   #     information.
>>   #
>> @@ -5316,6 +5317,18 @@ proc gdb_compile {source dest type options} {
>>   	lappend new_options "additional_flags=-Wl,--build-id"
>>       }
>>   
>> +    # If the 'no-build-id' option is used then disable the build-id.
>> +    if {[lsearch -exact $options no-build-id] > 0} {
>> +	lappend new_options "additional_flags=-Wl,--build-id=none"
>> +    }
>> +
>> +    # Sanity check.  If both 'build-id' and 'no-build-id' are used
>> +    # then what is expected from us!
>> +    if {[lsearch -exact $options build-id] > 0
>> +	&& [lsearch -exact $options no-build-id] > 0} {
>> +	error "cannot use build-id and no-build-id options"
>> +    }
>> +
>>       # Treating .c input files as C++ is deprecated in Clang, so
>>       # explicitly force C++ language.
>>       if { !$getting_compiler_info
>
>
> I've added the target: prefix for the set sysroot commands, and ran into 
> these three fails:
> ...
> FAIL: gdb.base/sysroot-debug-lookup.exp: lookup_via_build_id: [regexp 
> $re $::gdb_file_cmd_msg]
> FAIL: gdb.base/sysroot-debug-lookup.exp: lookup_via_debuglink: 
> $::gdb_file_cmd_debug_info eq "debug"
> FAIL: gdb.base/sysroot-debug-lookup.exp: lookup_via_debuglink: [regexp 
> $re $::gdb_file_cmd_msg]
> ...
>
> The first one is just due to gdb mentioning an unresolved symlink.

Yeah.  The build-id lookup w.r.t target: sysroots seems pretty sane.
I've extended the test to cover the target: case.

>
> But I think the next one reproduces PR30866.  So, IWBN to add this 
> dimension to the test-case and add a kfail.

I'm not 100% certain if the issue here is 30866 or not.  I can't
reproduce 30866, I think the namespace mounting support in GDB is not
working for me, for some reason.  I'll need to dig into this at some
future time.

However, if it's not exactly 30866, then it's certainly something like
30866!  So, for now I've added an xfail, blamed it on 30866, and figure
that if/when 30866 is fixed, if this test doesn't start working, we can
open a new bug at that time.

You did already approve, but given the changes I wanted to let you take
another look before I merged this.

Let me know if you have any further thoughts.

Thanks,
Andrew

---

commit bbdb9e9a479a6a2120a7abe1ce07d033b6e52b0c
Author: Andrew Burgess <aburgess@redhat.com>
Date:   Sat May 18 10:50:23 2024 +0100

    gdb/testsuite: tests for debug lookup within the sysroot
    
    Add tests for looking up debug information within the sysroot via both
    build-id and gnu_debuglink.
    
    I wanted to ensure that the gnu_debuglink test couldn't make use of
    build-ids, so I added the 'no-build-id' flag to gdb_compile.
    
    As these tests rely on setting the sysroot, if I'm running a
    dynamically linked executable, GDB will try to find all shared
    libraries within the sysroot.  This would mean I'd have to figure out
    and copy all shared libraries the executable uses, certainly possible,
    but a bit of a pain.
    
    So instead, I've just compiled the test executable as a static binary.
    Now there are no shared library dependencies.
    
    I can now split the debug information out from the test binary, and
    place it within the sysroot.  When GDB is started and the executable
    loaded, we can check that GDB is finding the debug information within
    the sysroot.
    
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30871
    
    Approved-By: Tom de Vries <tdevries@suse.de>

diff --git a/gdb/testsuite/gdb.base/sysroot-debug-lookup.exp b/gdb/testsuite/gdb.base/sysroot-debug-lookup.exp
new file mode 100644
index 00000000000..49e5b54fbd3
--- /dev/null
+++ b/gdb/testsuite/gdb.base/sysroot-debug-lookup.exp
@@ -0,0 +1,202 @@
+# Copyright 2024 Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test GDB's ability to find debug information by looking within the
+# sysroot.
+#
+# We compile a static binary (to reduce what we need to copy into the
+# sysroot), split the debug information from the binary, and setup a
+# sysroot.
+#
+# The debug-file-directory is set to just '/debug', but we're
+# expecting GDB to actually look in '$SYSROOT/debug'.
+#
+# There's a test for using .build-id based lookup, and a test for
+# gnu_debuglink based lookup.
+
+require {!is_remote host}
+
+standard_testfile main.c
+
+# Create a copy of BINFILE, split out the debug information, and then
+# setup a sysroot.  Hide (by moving) the actual debug information file
+# and create a symlink to the hidden debug information from within the
+# sysroot.
+#
+# Start GDB, set the sysroot, and then load the executable, ensure GDB
+# finds the debug information, which must have happened by lookin in
+# the sysroot.
+proc_with_prefix lookup_via_build_id {} {
+    set filename ${::binfile}_1
+    if { [build_executable "build exec" ${filename} $::srcfile \
+	      {additional_flags=-static debug build-id}] } {
+	return
+    }
+
+    # Split debug information into a .debug file, remove debug
+    # information from FILENAME.  Don't add a .gnu_debuglink to
+    # FILENAME, we rely on the build-id.
+    if {[gdb_gnu_strip_debug $filename { no-debuglink }] != 0} {
+	unsupported "cannot split debug information from executable"
+	return
+    }
+
+    set sysroot [standard_output_file "sysroot1"]
+    set debug_dir "/debug"
+
+    set debug_symlink \
+	${sysroot}${debug_dir}/[build_id_debug_filename_get $filename]
+
+    set build_id_dir [file dirname $debug_symlink]
+
+    set debug_filename ${filename}_hidden_debug
+
+    remote_exec build "mkdir -p $build_id_dir"
+    remote_exec build "mv $filename.debug $debug_filename"
+    remote_exec build "ln -sf $debug_filename $debug_symlink"
+
+    foreach_with_prefix sysroot_prefix { "" "target:" } {
+	clean_restart
+
+	gdb_test_no_output "set sysroot ${sysroot_prefix}$sysroot" "set sysroot"
+	gdb_test_no_output "set debug-file-directory $debug_dir"
+
+	gdb_file_cmd $filename
+
+	gdb_assert { $::gdb_file_cmd_debug_info eq "debug" } \
+	    "ensure debug information was found"
+
+	if { $sysroot_prefix eq "" } {
+	    set lookup_filename $debug_filename
+	} else {
+	    # Only when using the extended-remote board will we have
+	    # started a remote target by this point.  In this case GDB
+	    # will see the 'target:' prefix as remote, and so the
+	    # reported filename will include the 'target:' prefix.
+	    #
+	    # In all other cases we will still be using the default,
+	    # initial target, in which case GDB considers the
+	    # 'target:' prefix to indicate the local filesystem.
+	    if {[target_info gdb_protocol] == "extended-remote"} {
+		set lookup_filename $sysroot_prefix$debug_symlink
+	    } else {
+		set lookup_filename $debug_symlink
+	    }
+	}
+	set re [string_to_regexp "Reading symbols from $lookup_filename..."]
+	gdb_assert {[regexp $re $::gdb_file_cmd_msg]} \
+	    "debug symbols read from correct file"
+    }
+}
+
+# Create a copy of BINFILE, split out the debug information, and then
+# setup a sysroot.  Hide (by moving) the actual debug information file
+# and create a symlink to the hidden debug information from within the
+# sysroot.
+#
+# Copy the executable into the sysroot and then start GDB, set the
+# sysroot, and load the executable.  Check that GDB finds the debug
+# information, which must have happened by lookin in the sysroot.
+proc_with_prefix lookup_via_debuglink {} {
+    set filename ${::binfile}_2
+    if { [build_executable "build exec" ${filename} $::srcfile \
+	      {additional_flags=-static debug no-build-id}] } {
+	return
+    }
+
+    # Split debug information into a .debug file, remove debug
+    # information from FILENAME.
+    if {[gdb_gnu_strip_debug $filename] != 0} {
+	unsupported "cannot split debug information from executable"
+	return
+    }
+
+    # We're going to setup the sysroot like this:
+    #
+    # sysroot2/
+    #    bin/
+    #      $FILENAME
+    #    debug/
+    #      bin/
+    #        $FILENAME.debug
+    #
+    # When looking up debug information via the debuglink, GDB will
+    # only search in the sysroot if the original objfile was in the
+    # sysroot.  And GDB will resolve symlinks, so if the objfile is
+    # symlinked to outside the sysroot, GDB will not search in the
+    # sysroot for the debug information.
+    #
+    # So we have to copy the executable into the sysroot.
+    #
+    # We are OK to symlink the debug information to a file outside the
+    # sysroot though.
+
+    set sysroot [standard_output_file "sysroot2"]
+
+    foreach path { bin debug/bin } {
+	remote_exec build "mkdir -p $sysroot/$path"
+    }
+
+    # Copy the executable into the sysroot.
+    set file_basename [file tail $filename]
+    set exec_in_sysroot ${sysroot}/bin/${file_basename}
+    remote_exec build "cp $filename $exec_in_sysroot"
+
+    # Rename the debug file outside of the sysroot, this should stop
+    # GDB finding this file "by accident".
+    set debug_filename ${filename}_hidden_debug
+    remote_exec build "mv $filename.debug $debug_filename"
+
+    # Symlink the debug information into the sysroot.
+    set debug_symlink \
+	${sysroot}/debug/bin/${file_basename}.debug
+    remote_exec build "ln -sf $debug_filename $debug_symlink"
+
+    foreach_with_prefix sysroot_prefix { "" "target:" } {
+	# Restart GDB and setup the sysroot and debug directory.
+	clean_restart
+	gdb_test_no_output "set sysroot ${sysroot_prefix}$sysroot" "set sysroot"
+	gdb_test_no_output "set debug-file-directory /debug"
+
+	# Load the executable, we expect GDB to find the debug information
+	# in the sysroot.
+	gdb_file_cmd ${sysroot_prefix}$exec_in_sysroot
+
+	# Giving a sysroot a 'target:' prefix doesn't seem to work as
+	# might be expected for debug-link based lookups.  For this
+	# style of lookup GDB only seems to care if the original file
+	# itself had a 'target:' prefix.  The 'target:' prefix on the
+	# sysroot just seems to cause GDB to bail on looking up via
+	# the 'target:' prefixed sysroot.
+	#
+	# Bug PR gdb/30866 seems to be the (or a) relevant bug for
+	# this problem.
+	if { $sysroot_prefix ne "" } {
+	    setup_xfail "*-*-*" 30866
+	}
+	gdb_assert { $::gdb_file_cmd_debug_info eq "debug" } \
+	    "ensure debug information was found"
+
+	if { $sysroot_prefix ne "" } {
+	    setup_xfail "*-*-*" 30866
+	}
+	set re [string_to_regexp "Reading symbols from ${sysroot_prefix}$debug_symlink..."]
+	gdb_assert {[regexp $re $::gdb_file_cmd_msg]} \
+	    "debug symbols read from correct file"
+    }
+}
+
+lookup_via_build_id
+lookup_via_debuglink
diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index a63c13f9cbc..a8e8b69d6ef 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -5211,6 +5211,7 @@ proc quote_for_host { args } {
 #     debug information
 #   - text_segment=addr: Tell the linker to place the text segment at ADDR.
 #   - build-id: Ensure the final binary includes a build-id.
+#   - no-build-id: Ensure the final binary does not include a build-id.
 #   - column-info/no-column-info: Enable/Disable generation of column table
 #     information.
 #
@@ -5316,6 +5317,18 @@ proc gdb_compile {source dest type options} {
 	lappend new_options "additional_flags=-Wl,--build-id"
     }
 
+    # If the 'no-build-id' option is used then disable the build-id.
+    if {[lsearch -exact $options no-build-id] > 0} {
+	lappend new_options "additional_flags=-Wl,--build-id=none"
+    }
+
+    # Sanity check.  If both 'build-id' and 'no-build-id' are used
+    # then what is expected from us!
+    if {[lsearch -exact $options build-id] > 0
+	&& [lsearch -exact $options no-build-id] > 0} {
+	error "cannot use build-id and no-build-id options"
+    }
+
     # Treating .c input files as C++ is deprecated in Clang, so
     # explicitly force C++ language.
     if { !$getting_compiler_info
  

On 5/27/24 01:04, Andrew Burgess wrote:
> Tom de Vries <tdevries@suse.de> writes:
> 
>> On 5/20/24 16:14, Andrew Burgess wrote:
>>> Add tests for looking up debug information within the sysroot via both
>>> build-id and gnu_debuglink.
>>>
>>> I wanted to ensure that the gnu_debuglink test couldn't make use of
>>> build-ids, so I added the 'no-build-id' flag to gdb_compile.
>>>
>>> As these tests rely on setting the sysroot, if I'm running a
>>> dynamically linked executable, GDB will try to find all shared
>>> libraries within the sysroot.  This would mean I'd have to figure out
>>> and copy all shared libraries the executable uses, certainly possible,
>>> but a bit of a pain.
>>>
>>> So instead, I've just compiled the test executable as a static binary.
>>> Now there are no shared library dependencies.
>>>
>>
>> Make sense.
>>
>>> I can now split the debug information out from the test binary, and
>>> place it within the sysroot.  When GDB is started and the executable
>>> loaded, we can check that GDB is finding the debug information within
>>> the sysroot.
>>>
>>> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30871
>>> ---
>>>    gdb/testsuite/gdb.base/sysroot-debug-lookup.c |  22 +++
>>>    .../gdb.base/sysroot-debug-lookup.exp         | 162 ++++++++++++++++++
>>>    gdb/testsuite/lib/gdb.exp                     |  13 ++
>>>    3 files changed, 197 insertions(+)
>>>    create mode 100644 gdb/testsuite/gdb.base/sysroot-debug-lookup.c
>>>    create mode 100644 gdb/testsuite/gdb.base/sysroot-debug-lookup.exp
>>>
>>> diff --git a/gdb/testsuite/gdb.base/sysroot-debug-lookup.c b/gdb/testsuite/gdb.base/sysroot-debug-lookup.c
>>> new file mode 100644
>>> index 00000000000..e67331d3150
>>> --- /dev/null
>>> +++ b/gdb/testsuite/gdb.base/sysroot-debug-lookup.c
>>> @@ -0,0 +1,22 @@
>>> +/* This testcase is part of GDB, the GNU debugger.
>>> +
>>> +   Copyright 1992-2024 Free Software Foundation, Inc.
>>> +
>>> +   This program is free software; you can redistribute it and/or modify
>>> +   it under the terms of the GNU General Public License as published by
>>> +   the Free Software Foundation; either version 3 of the License, or
>>> +   (at your option) any later version.
>>> +
>>> +   This program is distributed in the hope that it will be useful,
>>> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>>> +   GNU General Public License for more details.
>>> +
>>> +   You should have received a copy of the GNU General Public License
>>> +   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
>>> +
>>> +int
>>> +main ()
>>> +{
>>> +  return 0;
>>> +}
>>> diff --git a/gdb/testsuite/gdb.base/sysroot-debug-lookup.exp b/gdb/testsuite/gdb.base/sysroot-debug-lookup.exp
>>> new file mode 100644
>>> index 00000000000..e0377df0fa7
>>> --- /dev/null
>>> +++ b/gdb/testsuite/gdb.base/sysroot-debug-lookup.exp
>>> @@ -0,0 +1,162 @@
>>> +# Copyright 2024 Free Software Foundation, Inc.
>>> +#
>>> +# This program is free software; you can redistribute it and/or modify
>>> +# it under the terms of the GNU General Public License as published by
>>> +# the Free Software Foundation; either version 3 of the License, or
>>> +# (at your option) any later version.
>>> +#
>>> +# This program is distributed in the hope that it will be useful,
>>> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>>> +# GNU General Public License for more details.
>>> +#
>>> +# You should have received a copy of the GNU General Public License
>>> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
>>> +
>>> +# Test GDB's ability to find debug information by looking within the
>>> +# sysroot.
>>> +#
>>> +# We compile a static binary (to reduce what we need to copy into the
>>> +# sysroot), split the debug information from the binary, and setup a
>>> +# sysroot.
>>> +#
>>> +# The debug-file-directory is set to just '/debug', but we're
>>> +# expecting GDB to actually look in '$SYSROOT/debug'.
>>> +#
>>> +# There's a test for using .build-id based lookup, and a test for
>>> +# gnu_debuglink based lookup.
>>> +
>>> +require {!is_remote host}
>>> +
>>> +standard_testfile
>>
>> Consider using "standard_testfile main.c" and dropping
>> gdb/testsuite/gdb.base/sysroot-debug-lookup.c.
> 
> Done.
> 
>>
>>> +
>>> +# Create a copy of BINFILE, split out the debug information, and then
>>> +# setup a sysroot.  Hide (by moving) the actual debug information file
>>> +# and create a symlink to the hidden debug information from within the
>>> +# sysroot.
>>> +#
>>> +# Start GDB, set the sysroot, and then load the executable, ensure GDB
>>> +# finds the debug information, which must have happened by lookin in
>>> +# the sysroot.
>>> +proc_with_prefix lookup_via_build_id {} {
>>> +    set filename ${::binfile}_1
>>> +    if { [build_executable "build exec" ${filename} $::srcfile \
>>> +	      {additional_flags=-static debug build-id}] } {
>>> +	return
>>> +    }
>>> +
>>> +    # Split debug information into a .debug file, remove debug
>>> +    # information from FILENAME.  Don't add a .gnu_debuglink to
>>> +    # FILENAME, we rely on the build-id.
>>> +    if {[gdb_gnu_strip_debug $filename { no-debuglink }] != 0} {
>>> +	unsupported "cannot split debug information from executable"
>>> +	return
>>> +    }
>>> +
>>> +    set sysroot [standard_output_file "sysroot1"]
>>> +    set debug_dir "/debug"
>>> +
>>> +    set debug_symlink \
>>> +	$sysroot/$debug_dir/[build_id_debug_filename_get $filename]
>>> +
>>> +    set build_id_dir [file dirname $debug_symlink]
>>> +
>>> +    set debug_filename ${filename}_hidden_debug
>>> +
>>> +    remote_exec build "mkdir -p $build_id_dir"
>>> +    remote_exec build "mv $filename.debug $debug_filename"
>>> +    remote_exec build "ln -sf $debug_filename $debug_symlink"
>>> +
>>> +    clean_restart
>>> +
>>> +    gdb_test_no_output "set sysroot $sysroot" "set sysroot"
>>> +    gdb_test_no_output "set debug-file-directory $debug_dir"
>>> +
>>> +    gdb_file_cmd $filename
>>> +
>>> +    gdb_assert { $::gdb_file_cmd_debug_info eq "debug" }
>>> +
>>> +    set re [string_to_regexp "Reading symbols from $debug_filename..."]
>>> +    gdb_assert {[regexp $re $::gdb_file_cmd_msg]}
>>
>> Consider adding a friendlier test name, likewise in the other proc.
>>
>> Currently we get for a fail the not very meaningful:
>> ...
>> FAIL: $exp: lookup_via_build_id: [regexp $re $::gdb_file_cmd_msg]
> 
> Done (I think).
> 
>> ...
>>
>>> +}
>>> +
>>> +# Create a copy of BINFILE, split out the debug information, and then
>>> +# setup a sysroot.  Hide (by moving) the actual debug information file
>>> +# and create a symlink to the hidden debug information from within the
>>> +# sysroot.
>>> +#
>>> +# Copy the executable into the sysroot and then start GDB, set the
>>> +# sysroot, and load the executable.  Check that GDB finds the debug
>>> +# information, which must have happened by lookin in the sysroot.
>>> +proc_with_prefix lookup_via_debuglink {} {
>>> +    set filename ${::binfile}_2
>>> +    if { [build_executable "build exec" ${filename} $::srcfile \
>>> +	      {additional_flags=-static debug no-build-id}] } {
>>> +	return
>>> +    }
>>> +
>>> +    # Split debug information into a .debug file, remove debug
>>> +    # information from FILENAME.
>>> +    if {[gdb_gnu_strip_debug $filename] != 0} {
>>> +	unsupported "cannot split debug information from executable"
>>> +	return
>>> +    }
>>> +
>>> +    # We're going to setup the sysroot like this:
>>> +    #
>>> +    # sysroot2/
>>> +    #    bin/
>>> +    #      $FILENAME
>>> +    #    debug/
>>> +    #      bin/
>>> +    #        $FILENAME.debug
>>> +    #
>>> +    # When looking up debug information via the debuglink, GDB will
>>> +    # only search in the sysroot if the original objfile was in the
>>> +    # sysroot.  And GDB will resolve symlinks, so if the objfile is
>>> +    # symlinked to outside the sysroot, GDB will not search in the
>>> +    # sysroot for the debug information.
>>> +    #
>>> +    # So we have to copy the executable into the sysroot.
>>> +    #
>>> +    # We are OK to symlink the debug information to a file outside the
>>> +    # sysroot though.
>>> +
>>> +    set sysroot [standard_output_file "sysroot2"]
>>> +
>>> +    foreach path { bin debug/bin } {
>>> +	remote_exec build "mkdir -p $sysroot/$path"
>>> +    }
>>> +
>>> +    # Copy the executable into the sysroot.
>>> +    set file_basename [file tail $filename]
>>> +    set exec_in_sysroot ${sysroot}/bin/${file_basename}
>>> +    remote_exec build "cp $filename $exec_in_sysroot"
>>> +
>>> +    # Rename the debug file outside of the sysroot, this should stop
>>> +    # GDB finding this file "by accident".
>>> +    set debug_filename ${filename}_hidden_debug
>>> +    remote_exec build "mv $filename.debug $debug_filename"
>>> +
>>> +    # Symlink the debug information into the sysroot.
>>> +    set debug_symlink \
>>> +	${sysroot}/debug/bin/${file_basename}.debug
>>> +    remote_exec build "ln -sf $debug_filename $debug_symlink"
>>> +
>>> +    # Restart GDB and setup the sysroot and debug directory.
>>> +    clean_restart
>>> +    gdb_test_no_output "set sysroot $sysroot" "set sysroot"
>>> +    gdb_test_no_output "set debug-file-directory /debug"
>>> +
>>> +    # Load the executable, we expect GDB to find the debug information
>>> +    # in the sysroot.
>>> +    gdb_file_cmd $exec_in_sysroot
>>> +
>>> +    gdb_assert { $::gdb_file_cmd_debug_info eq "debug" }
>>> +
>>> +    set re [string_to_regexp "Reading symbols from $debug_symlink..."]
>>> +    gdb_assert {[regexp $re $::gdb_file_cmd_msg]}
>>> +}
>>> +
>>> +lookup_via_build_id
>>> +lookup_via_debuglink
>>> diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
>>> index a63c13f9cbc..a8e8b69d6ef 100644
>>> --- a/gdb/testsuite/lib/gdb.exp
>>> +++ b/gdb/testsuite/lib/gdb.exp
>>> @@ -5211,6 +5211,7 @@ proc quote_for_host { args } {
>>>    #     debug information
>>>    #   - text_segment=addr: Tell the linker to place the text segment at ADDR.
>>>    #   - build-id: Ensure the final binary includes a build-id.
>>> +#   - no-build-id: Ensure the final binary does not include a build-id.
>>>    #   - column-info/no-column-info: Enable/Disable generation of column table
>>>    #     information.
>>>    #
>>> @@ -5316,6 +5317,18 @@ proc gdb_compile {source dest type options} {
>>>    	lappend new_options "additional_flags=-Wl,--build-id"
>>>        }
>>>    
>>> +    # If the 'no-build-id' option is used then disable the build-id.
>>> +    if {[lsearch -exact $options no-build-id] > 0} {
>>> +	lappend new_options "additional_flags=-Wl,--build-id=none"
>>> +    }
>>> +
>>> +    # Sanity check.  If both 'build-id' and 'no-build-id' are used
>>> +    # then what is expected from us!
>>> +    if {[lsearch -exact $options build-id] > 0
>>> +	&& [lsearch -exact $options no-build-id] > 0} {
>>> +	error "cannot use build-id and no-build-id options"
>>> +    }
>>> +
>>>        # Treating .c input files as C++ is deprecated in Clang, so
>>>        # explicitly force C++ language.
>>>        if { !$getting_compiler_info
>>
>>
>> I've added the target: prefix for the set sysroot commands, and ran into
>> these three fails:
>> ...
>> FAIL: gdb.base/sysroot-debug-lookup.exp: lookup_via_build_id: [regexp
>> $re $::gdb_file_cmd_msg]
>> FAIL: gdb.base/sysroot-debug-lookup.exp: lookup_via_debuglink:
>> $::gdb_file_cmd_debug_info eq "debug"
>> FAIL: gdb.base/sysroot-debug-lookup.exp: lookup_via_debuglink: [regexp
>> $re $::gdb_file_cmd_msg]
>> ...
>>
>> The first one is just due to gdb mentioning an unresolved symlink.
> 
> Yeah.  The build-id lookup w.r.t target: sysroots seems pretty sane.
> I've extended the test to cover the target: case.
> 
>>
>> But I think the next one reproduces PR30866.  So, IWBN to add this
>> dimension to the test-case and add a kfail.
> 
> I'm not 100% certain if the issue here is 30866 or not.  I can't
> reproduce 30866, I think the namespace mounting support in GDB is not
> working for me, for some reason.  I'll need to dig into this at some
> future time.
> 
> However, if it's not exactly 30866, then it's certainly something like
> 30866!  So, for now I've added an xfail, blamed it on 30866, and figure
> that if/when 30866 is fixed, if this test doesn't start working, we can
> open a new bug at that time.
> 
> You did already approve, but given the changes I wanted to let you take
> another look before I merged this.
> 
> Let me know if you have any further thoughts.
> 

Interesting.  Looking into it a bit further, I think it is indeed a 
different issue, thanks for pointing that out.  I filed a PR ( 
https://sourceware.org/bugzilla/show_bug.cgi?id=31804 ) for this, and 
investigated a bit and posted a demonstrator patch.

Anyway, please refer to this PR, and do so using a kfail, since AFAIU 
this a problem in gdb, not external to gdb.

Otherwise, LGTM.

Thanks,
- Tom

> Thanks,
> Andrew
> 
> ---
> 
> commit bbdb9e9a479a6a2120a7abe1ce07d033b6e52b0c
> Author: Andrew Burgess <aburgess@redhat.com>
> Date:   Sat May 18 10:50:23 2024 +0100
> 
>      gdb/testsuite: tests for debug lookup within the sysroot
>      
>      Add tests for looking up debug information within the sysroot via both
>      build-id and gnu_debuglink.
>      
>      I wanted to ensure that the gnu_debuglink test couldn't make use of
>      build-ids, so I added the 'no-build-id' flag to gdb_compile.
>      
>      As these tests rely on setting the sysroot, if I'm running a
>      dynamically linked executable, GDB will try to find all shared
>      libraries within the sysroot.  This would mean I'd have to figure out
>      and copy all shared libraries the executable uses, certainly possible,
>      but a bit of a pain.
>      
>      So instead, I've just compiled the test executable as a static binary.
>      Now there are no shared library dependencies.
>      
>      I can now split the debug information out from the test binary, and
>      place it within the sysroot.  When GDB is started and the executable
>      loaded, we can check that GDB is finding the debug information within
>      the sysroot.
>      
>      Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30871
>      
>      Approved-By: Tom de Vries <tdevries@suse.de>
> 
> diff --git a/gdb/testsuite/gdb.base/sysroot-debug-lookup.exp b/gdb/testsuite/gdb.base/sysroot-debug-lookup.exp
> new file mode 100644
> index 00000000000..49e5b54fbd3
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/sysroot-debug-lookup.exp
> @@ -0,0 +1,202 @@
> +# Copyright 2024 Free Software Foundation, Inc.
> +#
> +# This program is free software; you can redistribute it and/or modify
> +# it under the terms of the GNU General Public License as published by
> +# the Free Software Foundation; either version 3 of the License, or
> +# (at your option) any later version.
> +#
> +# This program is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +# GNU General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
> +
> +# Test GDB's ability to find debug information by looking within the
> +# sysroot.
> +#
> +# We compile a static binary (to reduce what we need to copy into the
> +# sysroot), split the debug information from the binary, and setup a
> +# sysroot.
> +#
> +# The debug-file-directory is set to just '/debug', but we're
> +# expecting GDB to actually look in '$SYSROOT/debug'.
> +#
> +# There's a test for using .build-id based lookup, and a test for
> +# gnu_debuglink based lookup.
> +
> +require {!is_remote host}
> +
> +standard_testfile main.c
> +
> +# Create a copy of BINFILE, split out the debug information, and then
> +# setup a sysroot.  Hide (by moving) the actual debug information file
> +# and create a symlink to the hidden debug information from within the
> +# sysroot.
> +#
> +# Start GDB, set the sysroot, and then load the executable, ensure GDB
> +# finds the debug information, which must have happened by lookin in
> +# the sysroot.
> +proc_with_prefix lookup_via_build_id {} {
> +    set filename ${::binfile}_1
> +    if { [build_executable "build exec" ${filename} $::srcfile \
> +	      {additional_flags=-static debug build-id}] } {
> +	return
> +    }
> +
> +    # Split debug information into a .debug file, remove debug
> +    # information from FILENAME.  Don't add a .gnu_debuglink to
> +    # FILENAME, we rely on the build-id.
> +    if {[gdb_gnu_strip_debug $filename { no-debuglink }] != 0} {
> +	unsupported "cannot split debug information from executable"
> +	return
> +    }
> +
> +    set sysroot [standard_output_file "sysroot1"]
> +    set debug_dir "/debug"
> +
> +    set debug_symlink \
> +	${sysroot}${debug_dir}/[build_id_debug_filename_get $filename]
> +
> +    set build_id_dir [file dirname $debug_symlink]
> +
> +    set debug_filename ${filename}_hidden_debug
> +
> +    remote_exec build "mkdir -p $build_id_dir"
> +    remote_exec build "mv $filename.debug $debug_filename"
> +    remote_exec build "ln -sf $debug_filename $debug_symlink"
> +
> +    foreach_with_prefix sysroot_prefix { "" "target:" } {
> +	clean_restart
> +
> +	gdb_test_no_output "set sysroot ${sysroot_prefix}$sysroot" "set sysroot"
> +	gdb_test_no_output "set debug-file-directory $debug_dir"
> +
> +	gdb_file_cmd $filename
> +
> +	gdb_assert { $::gdb_file_cmd_debug_info eq "debug" } \
> +	    "ensure debug information was found"
> +
> +	if { $sysroot_prefix eq "" } {
> +	    set lookup_filename $debug_filename
> +	} else {
> +	    # Only when using the extended-remote board will we have
> +	    # started a remote target by this point.  In this case GDB
> +	    # will see the 'target:' prefix as remote, and so the
> +	    # reported filename will include the 'target:' prefix.
> +	    #
> +	    # In all other cases we will still be using the default,
> +	    # initial target, in which case GDB considers the
> +	    # 'target:' prefix to indicate the local filesystem.
> +	    if {[target_info gdb_protocol] == "extended-remote"} {
> +		set lookup_filename $sysroot_prefix$debug_symlink
> +	    } else {
> +		set lookup_filename $debug_symlink
> +	    }
> +	}
> +	set re [string_to_regexp "Reading symbols from $lookup_filename..."]
> +	gdb_assert {[regexp $re $::gdb_file_cmd_msg]} \
> +	    "debug symbols read from correct file"
> +    }
> +}
> +
> +# Create a copy of BINFILE, split out the debug information, and then
> +# setup a sysroot.  Hide (by moving) the actual debug information file
> +# and create a symlink to the hidden debug information from within the
> +# sysroot.
> +#
> +# Copy the executable into the sysroot and then start GDB, set the
> +# sysroot, and load the executable.  Check that GDB finds the debug
> +# information, which must have happened by lookin in the sysroot.
> +proc_with_prefix lookup_via_debuglink {} {
> +    set filename ${::binfile}_2
> +    if { [build_executable "build exec" ${filename} $::srcfile \
> +	      {additional_flags=-static debug no-build-id}] } {
> +	return
> +    }
> +
> +    # Split debug information into a .debug file, remove debug
> +    # information from FILENAME.
> +    if {[gdb_gnu_strip_debug $filename] != 0} {
> +	unsupported "cannot split debug information from executable"
> +	return
> +    }
> +
> +    # We're going to setup the sysroot like this:
> +    #
> +    # sysroot2/
> +    #    bin/
> +    #      $FILENAME
> +    #    debug/
> +    #      bin/
> +    #        $FILENAME.debug
> +    #
> +    # When looking up debug information via the debuglink, GDB will
> +    # only search in the sysroot if the original objfile was in the
> +    # sysroot.  And GDB will resolve symlinks, so if the objfile is
> +    # symlinked to outside the sysroot, GDB will not search in the
> +    # sysroot for the debug information.
> +    #
> +    # So we have to copy the executable into the sysroot.
> +    #
> +    # We are OK to symlink the debug information to a file outside the
> +    # sysroot though.
> +
> +    set sysroot [standard_output_file "sysroot2"]
> +
> +    foreach path { bin debug/bin } {
> +	remote_exec build "mkdir -p $sysroot/$path"
> +    }
> +
> +    # Copy the executable into the sysroot.
> +    set file_basename [file tail $filename]
> +    set exec_in_sysroot ${sysroot}/bin/${file_basename}
> +    remote_exec build "cp $filename $exec_in_sysroot"
> +
> +    # Rename the debug file outside of the sysroot, this should stop
> +    # GDB finding this file "by accident".
> +    set debug_filename ${filename}_hidden_debug
> +    remote_exec build "mv $filename.debug $debug_filename"
> +
> +    # Symlink the debug information into the sysroot.
> +    set debug_symlink \
> +	${sysroot}/debug/bin/${file_basename}.debug
> +    remote_exec build "ln -sf $debug_filename $debug_symlink"
> +
> +    foreach_with_prefix sysroot_prefix { "" "target:" } {
> +	# Restart GDB and setup the sysroot and debug directory.
> +	clean_restart
> +	gdb_test_no_output "set sysroot ${sysroot_prefix}$sysroot" "set sysroot"
> +	gdb_test_no_output "set debug-file-directory /debug"
> +
> +	# Load the executable, we expect GDB to find the debug information
> +	# in the sysroot.
> +	gdb_file_cmd ${sysroot_prefix}$exec_in_sysroot
> +
> +	# Giving a sysroot a 'target:' prefix doesn't seem to work as
> +	# might be expected for debug-link based lookups.  For this
> +	# style of lookup GDB only seems to care if the original file
> +	# itself had a 'target:' prefix.  The 'target:' prefix on the
> +	# sysroot just seems to cause GDB to bail on looking up via
> +	# the 'target:' prefixed sysroot.
> +	#
> +	# Bug PR gdb/30866 seems to be the (or a) relevant bug for
> +	# this problem.
> +	if { $sysroot_prefix ne "" } {
> +	    setup_xfail "*-*-*" 30866
> +	}
> +	gdb_assert { $::gdb_file_cmd_debug_info eq "debug" } \
> +	    "ensure debug information was found"
> +
> +	if { $sysroot_prefix ne "" } {
> +	    setup_xfail "*-*-*" 30866
> +	}
> +	set re [string_to_regexp "Reading symbols from ${sysroot_prefix}$debug_symlink..."]
> +	gdb_assert {[regexp $re $::gdb_file_cmd_msg]} \
> +	    "debug symbols read from correct file"
> +    }
> +}
> +
> +lookup_via_build_id
> +lookup_via_debuglink
> diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
> index a63c13f9cbc..a8e8b69d6ef 100644
> --- a/gdb/testsuite/lib/gdb.exp
> +++ b/gdb/testsuite/lib/gdb.exp
> @@ -5211,6 +5211,7 @@ proc quote_for_host { args } {
>   #     debug information
>   #   - text_segment=addr: Tell the linker to place the text segment at ADDR.
>   #   - build-id: Ensure the final binary includes a build-id.
> +#   - no-build-id: Ensure the final binary does not include a build-id.
>   #   - column-info/no-column-info: Enable/Disable generation of column table
>   #     information.
>   #
> @@ -5316,6 +5317,18 @@ proc gdb_compile {source dest type options} {
>   	lappend new_options "additional_flags=-Wl,--build-id"
>       }
>   
> +    # If the 'no-build-id' option is used then disable the build-id.
> +    if {[lsearch -exact $options no-build-id] > 0} {
> +	lappend new_options "additional_flags=-Wl,--build-id=none"
> +    }
> +
> +    # Sanity check.  If both 'build-id' and 'no-build-id' are used
> +    # then what is expected from us!
> +    if {[lsearch -exact $options build-id] > 0
> +	&& [lsearch -exact $options no-build-id] > 0} {
> +	error "cannot use build-id and no-build-id options"
> +    }
> +
>       # Treating .c input files as C++ is deprecated in Clang, so
>       # explicitly force C++ language.
>       if { !$getting_compiler_info
>
  

Tom de Vries <tdevries@suse.de> writes:

> On 5/27/24 01:04, Andrew Burgess wrote:
>> Tom de Vries <tdevries@suse.de> writes:
>> 
>>> On 5/20/24 16:14, Andrew Burgess wrote:
>>>> Add tests for looking up debug information within the sysroot via both
>>>> build-id and gnu_debuglink.
>>>>
>>>> I wanted to ensure that the gnu_debuglink test couldn't make use of
>>>> build-ids, so I added the 'no-build-id' flag to gdb_compile.
>>>>
>>>> As these tests rely on setting the sysroot, if I'm running a
>>>> dynamically linked executable, GDB will try to find all shared
>>>> libraries within the sysroot.  This would mean I'd have to figure out
>>>> and copy all shared libraries the executable uses, certainly possible,
>>>> but a bit of a pain.
>>>>
>>>> So instead, I've just compiled the test executable as a static binary.
>>>> Now there are no shared library dependencies.
>>>>
>>>
>>> Make sense.
>>>
>>>> I can now split the debug information out from the test binary, and
>>>> place it within the sysroot.  When GDB is started and the executable
>>>> loaded, we can check that GDB is finding the debug information within
>>>> the sysroot.
>>>>
>>>> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30871
>>>> ---
>>>>    gdb/testsuite/gdb.base/sysroot-debug-lookup.c |  22 +++
>>>>    .../gdb.base/sysroot-debug-lookup.exp         | 162 ++++++++++++++++++
>>>>    gdb/testsuite/lib/gdb.exp                     |  13 ++
>>>>    3 files changed, 197 insertions(+)
>>>>    create mode 100644 gdb/testsuite/gdb.base/sysroot-debug-lookup.c
>>>>    create mode 100644 gdb/testsuite/gdb.base/sysroot-debug-lookup.exp
>>>>
>>>> diff --git a/gdb/testsuite/gdb.base/sysroot-debug-lookup.c b/gdb/testsuite/gdb.base/sysroot-debug-lookup.c
>>>> new file mode 100644
>>>> index 00000000000..e67331d3150
>>>> --- /dev/null
>>>> +++ b/gdb/testsuite/gdb.base/sysroot-debug-lookup.c
>>>> @@ -0,0 +1,22 @@
>>>> +/* This testcase is part of GDB, the GNU debugger.
>>>> +
>>>> +   Copyright 1992-2024 Free Software Foundation, Inc.
>>>> +
>>>> +   This program is free software; you can redistribute it and/or modify
>>>> +   it under the terms of the GNU General Public License as published by
>>>> +   the Free Software Foundation; either version 3 of the License, or
>>>> +   (at your option) any later version.
>>>> +
>>>> +   This program is distributed in the hope that it will be useful,
>>>> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
>>>> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>>>> +   GNU General Public License for more details.
>>>> +
>>>> +   You should have received a copy of the GNU General Public License
>>>> +   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
>>>> +
>>>> +int
>>>> +main ()
>>>> +{
>>>> +  return 0;
>>>> +}
>>>> diff --git a/gdb/testsuite/gdb.base/sysroot-debug-lookup.exp b/gdb/testsuite/gdb.base/sysroot-debug-lookup.exp
>>>> new file mode 100644
>>>> index 00000000000..e0377df0fa7
>>>> --- /dev/null
>>>> +++ b/gdb/testsuite/gdb.base/sysroot-debug-lookup.exp
>>>> @@ -0,0 +1,162 @@
>>>> +# Copyright 2024 Free Software Foundation, Inc.
>>>> +#
>>>> +# This program is free software; you can redistribute it and/or modify
>>>> +# it under the terms of the GNU General Public License as published by
>>>> +# the Free Software Foundation; either version 3 of the License, or
>>>> +# (at your option) any later version.
>>>> +#
>>>> +# This program is distributed in the hope that it will be useful,
>>>> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
>>>> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>>>> +# GNU General Public License for more details.
>>>> +#
>>>> +# You should have received a copy of the GNU General Public License
>>>> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
>>>> +
>>>> +# Test GDB's ability to find debug information by looking within the
>>>> +# sysroot.
>>>> +#
>>>> +# We compile a static binary (to reduce what we need to copy into the
>>>> +# sysroot), split the debug information from the binary, and setup a
>>>> +# sysroot.
>>>> +#
>>>> +# The debug-file-directory is set to just '/debug', but we're
>>>> +# expecting GDB to actually look in '$SYSROOT/debug'.
>>>> +#
>>>> +# There's a test for using .build-id based lookup, and a test for
>>>> +# gnu_debuglink based lookup.
>>>> +
>>>> +require {!is_remote host}
>>>> +
>>>> +standard_testfile
>>>
>>> Consider using "standard_testfile main.c" and dropping
>>> gdb/testsuite/gdb.base/sysroot-debug-lookup.c.
>> 
>> Done.
>> 
>>>
>>>> +
>>>> +# Create a copy of BINFILE, split out the debug information, and then
>>>> +# setup a sysroot.  Hide (by moving) the actual debug information file
>>>> +# and create a symlink to the hidden debug information from within the
>>>> +# sysroot.
>>>> +#
>>>> +# Start GDB, set the sysroot, and then load the executable, ensure GDB
>>>> +# finds the debug information, which must have happened by lookin in
>>>> +# the sysroot.
>>>> +proc_with_prefix lookup_via_build_id {} {
>>>> +    set filename ${::binfile}_1
>>>> +    if { [build_executable "build exec" ${filename} $::srcfile \
>>>> +	      {additional_flags=-static debug build-id}] } {
>>>> +	return
>>>> +    }
>>>> +
>>>> +    # Split debug information into a .debug file, remove debug
>>>> +    # information from FILENAME.  Don't add a .gnu_debuglink to
>>>> +    # FILENAME, we rely on the build-id.
>>>> +    if {[gdb_gnu_strip_debug $filename { no-debuglink }] != 0} {
>>>> +	unsupported "cannot split debug information from executable"
>>>> +	return
>>>> +    }
>>>> +
>>>> +    set sysroot [standard_output_file "sysroot1"]
>>>> +    set debug_dir "/debug"
>>>> +
>>>> +    set debug_symlink \
>>>> +	$sysroot/$debug_dir/[build_id_debug_filename_get $filename]
>>>> +
>>>> +    set build_id_dir [file dirname $debug_symlink]
>>>> +
>>>> +    set debug_filename ${filename}_hidden_debug
>>>> +
>>>> +    remote_exec build "mkdir -p $build_id_dir"
>>>> +    remote_exec build "mv $filename.debug $debug_filename"
>>>> +    remote_exec build "ln -sf $debug_filename $debug_symlink"
>>>> +
>>>> +    clean_restart
>>>> +
>>>> +    gdb_test_no_output "set sysroot $sysroot" "set sysroot"
>>>> +    gdb_test_no_output "set debug-file-directory $debug_dir"
>>>> +
>>>> +    gdb_file_cmd $filename
>>>> +
>>>> +    gdb_assert { $::gdb_file_cmd_debug_info eq "debug" }
>>>> +
>>>> +    set re [string_to_regexp "Reading symbols from $debug_filename..."]
>>>> +    gdb_assert {[regexp $re $::gdb_file_cmd_msg]}
>>>
>>> Consider adding a friendlier test name, likewise in the other proc.
>>>
>>> Currently we get for a fail the not very meaningful:
>>> ...
>>> FAIL: $exp: lookup_via_build_id: [regexp $re $::gdb_file_cmd_msg]
>> 
>> Done (I think).
>> 
>>> ...
>>>
>>>> +}
>>>> +
>>>> +# Create a copy of BINFILE, split out the debug information, and then
>>>> +# setup a sysroot.  Hide (by moving) the actual debug information file
>>>> +# and create a symlink to the hidden debug information from within the
>>>> +# sysroot.
>>>> +#
>>>> +# Copy the executable into the sysroot and then start GDB, set the
>>>> +# sysroot, and load the executable.  Check that GDB finds the debug
>>>> +# information, which must have happened by lookin in the sysroot.
>>>> +proc_with_prefix lookup_via_debuglink {} {
>>>> +    set filename ${::binfile}_2
>>>> +    if { [build_executable "build exec" ${filename} $::srcfile \
>>>> +	      {additional_flags=-static debug no-build-id}] } {
>>>> +	return
>>>> +    }
>>>> +
>>>> +    # Split debug information into a .debug file, remove debug
>>>> +    # information from FILENAME.
>>>> +    if {[gdb_gnu_strip_debug $filename] != 0} {
>>>> +	unsupported "cannot split debug information from executable"
>>>> +	return
>>>> +    }
>>>> +
>>>> +    # We're going to setup the sysroot like this:
>>>> +    #
>>>> +    # sysroot2/
>>>> +    #    bin/
>>>> +    #      $FILENAME
>>>> +    #    debug/
>>>> +    #      bin/
>>>> +    #        $FILENAME.debug
>>>> +    #
>>>> +    # When looking up debug information via the debuglink, GDB will
>>>> +    # only search in the sysroot if the original objfile was in the
>>>> +    # sysroot.  And GDB will resolve symlinks, so if the objfile is
>>>> +    # symlinked to outside the sysroot, GDB will not search in the
>>>> +    # sysroot for the debug information.
>>>> +    #
>>>> +    # So we have to copy the executable into the sysroot.
>>>> +    #
>>>> +    # We are OK to symlink the debug information to a file outside the
>>>> +    # sysroot though.
>>>> +
>>>> +    set sysroot [standard_output_file "sysroot2"]
>>>> +
>>>> +    foreach path { bin debug/bin } {
>>>> +	remote_exec build "mkdir -p $sysroot/$path"
>>>> +    }
>>>> +
>>>> +    # Copy the executable into the sysroot.
>>>> +    set file_basename [file tail $filename]
>>>> +    set exec_in_sysroot ${sysroot}/bin/${file_basename}
>>>> +    remote_exec build "cp $filename $exec_in_sysroot"
>>>> +
>>>> +    # Rename the debug file outside of the sysroot, this should stop
>>>> +    # GDB finding this file "by accident".
>>>> +    set debug_filename ${filename}_hidden_debug
>>>> +    remote_exec build "mv $filename.debug $debug_filename"
>>>> +
>>>> +    # Symlink the debug information into the sysroot.
>>>> +    set debug_symlink \
>>>> +	${sysroot}/debug/bin/${file_basename}.debug
>>>> +    remote_exec build "ln -sf $debug_filename $debug_symlink"
>>>> +
>>>> +    # Restart GDB and setup the sysroot and debug directory.
>>>> +    clean_restart
>>>> +    gdb_test_no_output "set sysroot $sysroot" "set sysroot"
>>>> +    gdb_test_no_output "set debug-file-directory /debug"
>>>> +
>>>> +    # Load the executable, we expect GDB to find the debug information
>>>> +    # in the sysroot.
>>>> +    gdb_file_cmd $exec_in_sysroot
>>>> +
>>>> +    gdb_assert { $::gdb_file_cmd_debug_info eq "debug" }
>>>> +
>>>> +    set re [string_to_regexp "Reading symbols from $debug_symlink..."]
>>>> +    gdb_assert {[regexp $re $::gdb_file_cmd_msg]}
>>>> +}
>>>> +
>>>> +lookup_via_build_id
>>>> +lookup_via_debuglink
>>>> diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
>>>> index a63c13f9cbc..a8e8b69d6ef 100644
>>>> --- a/gdb/testsuite/lib/gdb.exp
>>>> +++ b/gdb/testsuite/lib/gdb.exp
>>>> @@ -5211,6 +5211,7 @@ proc quote_for_host { args } {
>>>>    #     debug information
>>>>    #   - text_segment=addr: Tell the linker to place the text segment at ADDR.
>>>>    #   - build-id: Ensure the final binary includes a build-id.
>>>> +#   - no-build-id: Ensure the final binary does not include a build-id.
>>>>    #   - column-info/no-column-info: Enable/Disable generation of column table
>>>>    #     information.
>>>>    #
>>>> @@ -5316,6 +5317,18 @@ proc gdb_compile {source dest type options} {
>>>>    	lappend new_options "additional_flags=-Wl,--build-id"
>>>>        }
>>>>    
>>>> +    # If the 'no-build-id' option is used then disable the build-id.
>>>> +    if {[lsearch -exact $options no-build-id] > 0} {
>>>> +	lappend new_options "additional_flags=-Wl,--build-id=none"
>>>> +    }
>>>> +
>>>> +    # Sanity check.  If both 'build-id' and 'no-build-id' are used
>>>> +    # then what is expected from us!
>>>> +    if {[lsearch -exact $options build-id] > 0
>>>> +	&& [lsearch -exact $options no-build-id] > 0} {
>>>> +	error "cannot use build-id and no-build-id options"
>>>> +    }
>>>> +
>>>>        # Treating .c input files as C++ is deprecated in Clang, so
>>>>        # explicitly force C++ language.
>>>>        if { !$getting_compiler_info
>>>
>>>
>>> I've added the target: prefix for the set sysroot commands, and ran into
>>> these three fails:
>>> ...
>>> FAIL: gdb.base/sysroot-debug-lookup.exp: lookup_via_build_id: [regexp
>>> $re $::gdb_file_cmd_msg]
>>> FAIL: gdb.base/sysroot-debug-lookup.exp: lookup_via_debuglink:
>>> $::gdb_file_cmd_debug_info eq "debug"
>>> FAIL: gdb.base/sysroot-debug-lookup.exp: lookup_via_debuglink: [regexp
>>> $re $::gdb_file_cmd_msg]
>>> ...
>>>
>>> The first one is just due to gdb mentioning an unresolved symlink.
>> 
>> Yeah.  The build-id lookup w.r.t target: sysroots seems pretty sane.
>> I've extended the test to cover the target: case.
>> 
>>>
>>> But I think the next one reproduces PR30866.  So, IWBN to add this
>>> dimension to the test-case and add a kfail.
>> 
>> I'm not 100% certain if the issue here is 30866 or not.  I can't
>> reproduce 30866, I think the namespace mounting support in GDB is not
>> working for me, for some reason.  I'll need to dig into this at some
>> future time.
>> 
>> However, if it's not exactly 30866, then it's certainly something like
>> 30866!  So, for now I've added an xfail, blamed it on 30866, and figure
>> that if/when 30866 is fixed, if this test doesn't start working, we can
>> open a new bug at that time.
>> 
>> You did already approve, but given the changes I wanted to let you take
>> another look before I merged this.
>> 
>> Let me know if you have any further thoughts.
>> 
>
> Interesting.  Looking into it a bit further, I think it is indeed a 
> different issue, thanks for pointing that out.  I filed a PR ( 
> https://sourceware.org/bugzilla/show_bug.cgi?id=31804 ) for this, and 
> investigated a bit and posted a demonstrator patch.
>
> Anyway, please refer to this PR, and do so using a kfail, since AFAIU 
> this a problem in gdb, not external to gdb.
>
> Otherwise, LGTM.

I changed to kfail, updated the bug number to 31804, and pushed this
series.

Thanks for your feedback,
Andrew