[v2] gdb/testsuite: Add relative versus absolute LD_LIBRARY_PATH test

  At one time, circa 2006, there was a bug, which was presumably fixed
without adding a test case:

    If you provided some relative path to the shared library, such as
    with

	export LD_LIBRARY_PATH=.

    then gdb would fail to match the shared library name during the
    TLS lookup.

I think there may have been a bit more to it than is provided by that
explanation, since the test also takes care to split the debug info
into a separate file.

In any case, this commit is based on one of Red Hat's really old
local patches.  I've attempted to update it and remove a fair amount
of cruft, hopefully without losing any critical elements from the
test.

Testing on Fedora 38 (correctly) shows 1 unsupported test for
native-gdbserver and 5 PASSes for the native target as well as
native-extended-gdbserver.

In his review of v1 of this patch, Lancelot SIX observed that
'thread_local' could be used in place of '__thread' in the C source
files.  But it only became available via the standard in C11, so I
used additional_flags=-std=c11 for compiling both the shared object
and the main program.

Also, while testing with CC_FOR_TARGET=clang, I found that
'additional_flags=-Wl,-soname=${binsharedbase}' caused clang
to complain that this linker flag was unused when compiling
the source file, so I moved this linker option to 'ldflags='.

My testing for this v2 patch shows the same results as with v1,
but I've done additional testing with CC_FOR_TARGET=clang as
well.  The results are the same as when gcc is used.

Co-Authored-by: Jan Kratochvil <jan@jankratochvil.net>
Reviewed-by: Lancelot SIX <lsix@lancelotsix.com>
---
 gdb/testsuite/gdb.threads/tls-sepdebug-main.c | 29 ++++++
 .../gdb.threads/tls-sepdebug-shared.c         | 21 ++++
 gdb/testsuite/gdb.threads/tls-sepdebug.exp    | 95 +++++++++++++++++++
 3 files changed, 145 insertions(+)
 create mode 100644 gdb/testsuite/gdb.threads/tls-sepdebug-main.c
 create mode 100644 gdb/testsuite/gdb.threads/tls-sepdebug-shared.c
 create mode 100644 gdb/testsuite/gdb.threads/tls-sepdebug.exp
  

Hi Kevin,

FWIW, the patch looks good to me.  I do have one extra small detail
inlined below.

With that small fix (tested locally),
Reviewed-By: Lancelot Six <lancelot.six@amd.com>

Best,
Lancelot.

> diff --git a/gdb/testsuite/gdb.threads/tls-sepdebug.exp b/gdb/testsuite/gdb.threads/tls-sepdebug.exp
> new file mode 100644
> index 00000000000..1be1674fab1
> --- /dev/null
> +++ b/gdb/testsuite/gdb.threads/tls-sepdebug.exp
> @@ -0,0 +1,95 @@
> +# Copyright 2006-2023 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/>.
> +
> +# This test creates a shared library and a main program which uses
> +# that library, extracts the debug info of the library to a separate
> +# file, and then tests that a symbol from the shared library is
> +# accessible using both absolute and relative settings of
> +# LD_LIBRARY_PATH.
> +
> +# This test needs to change the environment in which the test program
> +# is run, specifically the setting of LD_LIBRARY_PATH.  GDB can adjust
> +# this setting for both native and extended-remote targets, but not
> +# for targets to which GDB connects after the program has already
> +# started.  Therefore, this test won't work for targets which use
> +# "target remote".
> +require !use_gdb_stub
> +require {have_compile_flag -std=c11}
> +
> +set testfile tls-sepdebug
> +set srcmainfile   ${testfile}-main.c
> +set srcsharedfile ${testfile}-shared.c
> +
> +set binmainfile        [standard_output_file ${testfile}-main]
> +set binsharedbase      ${testfile}-shared.so
> +set binsharedfile      [standard_output_file ${binsharedbase}]
> +
> +# Build the shared library, but use explicit -soname; otherwise the
> +# full path to the library would get encoded into ${binmainfile}
> +# making LD_LIBRARY_PATH tests useless.
> +#
> +# The compile flag -std=c11 is required because the test case uses
> +# 'thread_local' to indicate thread local storage.  This is available
> +# as a macro starting in C11 and became a C-language keyword in C23.
> +if  { [gdb_compile_shlib \
> +	"${srcdir}/${subdir}/${srcsharedfile}" "${binsharedfile}" \
> +	[list debug \
> +	      ldflags=-Wl,-soname=${binsharedbase} \
> +	      additional_flags=-std=c11]] \
> +       != "" } {
> +    untested "Couldn't compile test library"
> +    return -1
> +}
> +
> +# Strip debug information from $binsharedfile, placing it in
> +# ${binsharedfile}.debug.  Also add a .gnu_debuglink in the former,
> +# pointing to the latter.
> +gdb_gnu_strip_debug ${binsharedfile}
> +
> +# Build main program, but do not use `shlib=' since that would
> +# automatically add -rpath for gcc.
> +if  { [gdb_compile_pthreads \
> +	"${srcdir}/${subdir}/${srcmainfile} ${binsharedfile}" \
> +	"${binmainfile}" executable [list debug additional_flags=-std=c11]] \
> +       != "" } {
> +    untested "Couldn't compile test program"
> +    return -1
> +}
> +
> +set absdir [file dirname [standard_output_file ${binsharedbase}]]
> +
> +foreach ld_library_path [list $absdir [relative_filename [pwd] $absdir]] \
> +	name { absolute relative } {
> +    with_test_prefix $name {
> +
> +	# Restart, but defer loading until after setting LD_LIBRARY_PATH.
> +	clean_restart
> +
> +	gdb_test_no_output "set env LD_LIBRARY_PATH=$ld_library_path" \
> +			   "set env LD_LIBRARY_PATH"
> +
> +	gdb_load ${binmainfile}
> +
> +	if ![runto_main] {
> +	    return
> +	}
> +
> +	# Print a thread local variable from the shared library to be certain
> +	# that its symbols were loaded from the separate debuginfo file.
> +	gdb_test "print var" \
> +		 "\\\$1 = \[0-9\].*" \

I think here you can be more specific as you know the actual value which
is expected:

                 "\\\$1 = 42"

> +		 "print TLS variable from a shared library with separate debug info file"
> +    }
> +}
> -- 
> 2.41.0
>
  

On Thu, 28 Sep 2023 12:05:45 +0100
Lancelot SIX <lsix@lancelotsix.com> wrote:

> FWIW, the patch looks good to me.  I do have one extra small detail
> inlined below.
> 
> With that small fix (tested locally),
> Reviewed-By: Lancelot Six <lancelot.six@amd.com>
[...]
> I think here you can be more specific as you know the actual value which
> is expected:
> 
>                  "\\\$1 = 42"

I've made this change, added your Reviewed-by, and pushed this commit.

Thanks for your reviews!

Kevin