[v2] gdb/configure.ac: Add option --with-additional-debug-dirs

  If you want to install GDB in a custom prefix, have it look for debug info
in that prefix but also in the distro's default location (typically,
/usr/lib/debug) and run the GDB testsuite before doing "make install", you
have a bit of a problem:

Configuring GDB with '--prefix=$PREFIX' sets the GDB 'debug-file-directory'
parameter to $PREFIX/lib/debug.  Unfortunately this precludes GDB from
looking for distro-installed debug info in /usr/lib/debug.  For regular GDB
use you could set debug-file-directory to $PREFIX:/usr/lib/debug in
$PREFIX/etc/gdbinit so that GDB will look in both places, but if you want
to run the testsuite then that doesn't help because in that case GDB runs
with the '-nx' option.

There's the configure option '--with-separate-debug-dir' to set the default
value for 'debug-file-directory', but it accepts only one directory and not
a list.  I considered modifying it to accept a list, but it's not obvious
how to do that because its value is also used by BFD, as well as processed
for "relocatability".

I thought it was simpler to add a new option to specify a list of
additional directories that will be appended to the debug-file-directory
setting.
---
 gdb/NEWS            |  8 ++++++++
 gdb/config.in       |  3 +++
 gdb/configure       | 19 +++++++++++++++++--
 gdb/configure.ac    |  8 ++++++++
 gdb/doc/gdb.texinfo |  6 ++++--
 gdb/main.c          |  5 +++++
 gdb/top.c           |  6 ++++++
 7 files changed, 51 insertions(+), 4 deletions(-)

Changed since v1:
Addressed Tom Tromey's review comments:
- Added NEWS entry for the new configure option.
- Documented the new configure option in the GDB manual.
- Properly indented the body of AC_ARG_WITH.
- Added parentheses around RHS side of the assignment in gdb/main.c.


base-commit: 1181bcd0d2572aee2c0947040e56bc1f9af634e3
  

> Cc: Tom Tromey <tom@tromey.com>
> Date: Wed,  4 Oct 2023 15:31:02 -0300
> From: Thiago Jung Bauermann via Gdb-patches <gdb-patches@sourceware.org>
> 
> If you want to install GDB in a custom prefix, have it look for debug info
> in that prefix but also in the distro's default location (typically,
> /usr/lib/debug) and run the GDB testsuite before doing "make install", you
> have a bit of a problem:
> 
> Configuring GDB with '--prefix=$PREFIX' sets the GDB 'debug-file-directory'
> parameter to $PREFIX/lib/debug.  Unfortunately this precludes GDB from
> looking for distro-installed debug info in /usr/lib/debug.  For regular GDB
> use you could set debug-file-directory to $PREFIX:/usr/lib/debug in
> $PREFIX/etc/gdbinit so that GDB will look in both places, but if you want
> to run the testsuite then that doesn't help because in that case GDB runs
> with the '-nx' option.
> 
> There's the configure option '--with-separate-debug-dir' to set the default
> value for 'debug-file-directory', but it accepts only one directory and not
> a list.  I considered modifying it to accept a list, but it's not obvious
> how to do that because its value is also used by BFD, as well as processed
> for "relocatability".
> 
> I thought it was simpler to add a new option to specify a list of
> additional directories that will be appended to the debug-file-directory
> setting.

Thanks, the documentation parts are okay.

However, I wonder: on MS-Windows, the "colon-separated list" becomes
"semi-colon separated list", and I have an old and annoying problem
with 2 similar configure-time options, --with-auto-load-safe-path= and
--with-auto-load-dir=, which fail to communicate semi-colon separated
lists to gdb/configure, and require me to manually edit gdb/config.h
and rebuild.  So I wonder whether this new option will have the same
problem, and whether we could perhaps take this opportunity for fixing
this?

This is https://sourceware.org/bugzilla/show_bug.cgi?id=18898, btw.

Reviewed-By: Eli Zaretskii <eliz@gnu.org>
  

>>>>> "Thiago" == Thiago Jung Bauermann via Gdb-patches <gdb-patches@sourceware.org> writes:

Thiago> If you want to install GDB in a custom prefix, have it look for debug info
Thiago> in that prefix but also in the distro's default location (typically,
Thiago> /usr/lib/debug) and run the GDB testsuite before doing "make install", you
Thiago> have a bit of a problem:

...

Thank you.  This is ok.
Approved-By: Tom Tromey <tom@tromey.com>

Tom
  

Eli Zaretskii <eliz@gnu.org> writes:

>> Cc: Tom Tromey <tom@tromey.com>
>> Date: Wed,  4 Oct 2023 15:31:02 -0300
>> From: Thiago Jung Bauermann via Gdb-patches <gdb-patches@sourceware.org>
>> 
>> If you want to install GDB in a custom prefix, have it look for debug info
>> in that prefix but also in the distro's default location (typically,
>> /usr/lib/debug) and run the GDB testsuite before doing "make install", you
>> have a bit of a problem:
>> 
>> Configuring GDB with '--prefix=$PREFIX' sets the GDB 'debug-file-directory'
>> parameter to $PREFIX/lib/debug.  Unfortunately this precludes GDB from
>> looking for distro-installed debug info in /usr/lib/debug.  For regular GDB
>> use you could set debug-file-directory to $PREFIX:/usr/lib/debug in
>> $PREFIX/etc/gdbinit so that GDB will look in both places, but if you want
>> to run the testsuite then that doesn't help because in that case GDB runs
>> with the '-nx' option.
>> 
>> There's the configure option '--with-separate-debug-dir' to set the default
>> value for 'debug-file-directory', but it accepts only one directory and not
>> a list.  I considered modifying it to accept a list, but it's not obvious
>> how to do that because its value is also used by BFD, as well as processed
>> for "relocatability".
>> 
>> I thought it was simpler to add a new option to specify a list of
>> additional directories that will be appended to the debug-file-directory
>> setting.
>
> Thanks, the documentation parts are okay.

Thank you!

> However, I wonder: on MS-Windows, the "colon-separated list" becomes
> "semi-colon separated list", and I have an old and annoying problem
> with 2 similar configure-time options, --with-auto-load-safe-path= and
> --with-auto-load-dir=, which fail to communicate semi-colon separated
> lists to gdb/configure, and require me to manually edit gdb/config.h
> and rebuild.  So I wonder whether this new option will have the same
> problem, and whether we could perhaps take this opportunity for fixing
> this?
>
> This is https://sourceware.org/bugzilla/show_bug.cgi?id=18898, btw.

I looked a bit into this, and I don't see an easy solution. The problem
is that shell scripting language is notoriously bad at keeping data from
leaking into the code.

If I do:

$ ~/src/binutils-gdb/configure \
    --disable-{binutils,ld,gold,gas,sim,gprof,gprofng} \
    --with-auto-load-dir='foo;bar' && make

I get:

checking for default auto-load directory... /home/bauermann/src/binutils-gdb/gdb/configure: line 18004: bar: command not found
foo;bar
checking for default auto-load safe-path... /home/bauermann/src/binutils-gdb/gdb/configure: line 18031: bar: command not found
foo;bar

Line 18004 is:

ac_define_dir=`eval echo $escape_dir`

Line 18031 is identical.

If the configure script could use bash features instead of having to
assume a POSIX shell, we could use "printf %q" to escape the input. Is
there an equivalent solution that's in POSIX shell?

In any case, any solution would be in an autoconf macro, not in GDB.

As a workaround, I was able to get away with some escaping:

$ ~/src/binutils-gdb/configure \
    --disable-{binutils,ld,gold,gas,sim,gprof,gprofng} \
    --with-auto-load-dir='foo\\\;bar\\\;baz' && make
    ⋮
checking for default auto-load directory... foo\\\;bar\\\;baz
checking for default auto-load safe-path... foo\\\;bar\\\;baz
    ⋮
$ grep AUTO_LOAD gdb/config.h
#define AUTO_LOAD_DIR "foo;bar;baz"
#define AUTO_LOAD_SAFE_PATH "foo;bar;baz"


> Reviewed-By: Eli Zaretskii <eliz@gnu.org>
  

Tom Tromey <tom@tromey.com> writes:

>>>>>> "Thiago" == Thiago Jung Bauermann via Gdb-patches <gdb-patches@sourceware.org>
> writes:
>
> Thiago> If you want to install GDB in a custom prefix, have it look for debug info
> Thiago> in that prefix but also in the distro's default location (typically,
> Thiago> /usr/lib/debug) and run the GDB testsuite before doing "make install", you
> Thiago> have a bit of a problem:
>
> ...
>
> Thank you.  This is ok.
> Approved-By: Tom Tromey <tom@tromey.com>

Thanks! Pushed as commit 740ce35025a5.
  

> From: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
> Cc: gdb-patches@sourceware.org, tom@tromey.com
> Date: Thu, 05 Oct 2023 20:12:17 -0300
> 
> As a workaround, I was able to get away with some escaping:
> 
> $ ~/src/binutils-gdb/configure \
>     --disable-{binutils,ld,gold,gas,sim,gprof,gprofng} \
>     --with-auto-load-dir='foo\\\;bar\\\;baz' && make
>     ⋮
> checking for default auto-load directory... foo\\\;bar\\\;baz
> checking for default auto-load safe-path... foo\\\;bar\\\;baz
>     ⋮
> $ grep AUTO_LOAD gdb/config.h
> #define AUTO_LOAD_DIR "foo;bar;baz"
> #define AUTO_LOAD_SAFE_PATH "foo;bar;baz"

Thanks, will use these in my next build, and see if it works for me as
well.
  

> Date: Sat, 07 Oct 2023 10:01:52 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: gdb-patches@sourceware.org, tom@tromey.com
> X-Spam-Status: No, score=0.6 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH,
>  DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, SPF_HELO_PASS, SPF_PASS,
>  TXREP autolearn=ham autolearn_force=no version=3.4.6
> 
> > From: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
> > Cc: gdb-patches@sourceware.org, tom@tromey.com
> > Date: Thu, 05 Oct 2023 20:12:17 -0300
> > 
> > As a workaround, I was able to get away with some escaping:
> > 
> > $ ~/src/binutils-gdb/configure \
> >     --disable-{binutils,ld,gold,gas,sim,gprof,gprofng} \
> >     --with-auto-load-dir='foo\\\;bar\\\;baz' && make
> >     ⋮
> > checking for default auto-load directory... foo\\\;bar\\\;baz
> > checking for default auto-load safe-path... foo\\\;bar\\\;baz
> >     ⋮
> > $ grep AUTO_LOAD gdb/config.h
> > #define AUTO_LOAD_DIR "foo;bar;baz"
> > #define AUTO_LOAD_SAFE_PATH "foo;bar;baz"
> 
> Thanks, will use these in my next build, and see if it works for me as
> well.

FTR: just tried this with the gdb-14.0.91 pretest, and it works just
fine.  Thank you very much for helping me avoid this annoying problem
(it previously required me to build GDB twice).

I've updated the Bugzilla bug with this information.

Thanks!
  

Hello Eli,

Eli Zaretskii <eliz@gnu.org> writes:

>> Date: Sat, 07 Oct 2023 10:01:52 +0300
>> From: Eli Zaretskii <eliz@gnu.org>
>> Cc: gdb-patches@sourceware.org, tom@tromey.com
>> X-Spam-Status: No, score=0.6 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH,
>>  DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, SPF_HELO_PASS, SPF_PASS,
>>  TXREP autolearn=ham autolearn_force=no version=3.4.6
>> 
>> > From: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
>> > Cc: gdb-patches@sourceware.org, tom@tromey.com
>> > Date: Thu, 05 Oct 2023 20:12:17 -0300
>> > 
>> > As a workaround, I was able to get away with some escaping:
>> > 
>> > $ ~/src/binutils-gdb/configure \
>> >     --disable-{binutils,ld,gold,gas,sim,gprof,gprofng} \
>> >     --with-auto-load-dir='foo\\\;bar\\\;baz' && make
>> >     ⋮
>> > checking for default auto-load directory... foo\\\;bar\\\;baz
>> > checking for default auto-load safe-path... foo\\\;bar\\\;baz
>> >     ⋮
>> > $ grep AUTO_LOAD gdb/config.h
>> > #define AUTO_LOAD_DIR "foo;bar;baz"
>> > #define AUTO_LOAD_SAFE_PATH "foo;bar;baz"
>> 
>> Thanks, will use these in my next build, and see if it works for me as
>> well.
>
> FTR: just tried this with the gdb-14.0.91 pretest, and it works just
> fine.  Thank you very much for helping me avoid this annoying problem
> (it previously required me to build GDB twice).

Excellent! I poked at it some more today and I noticed two things:

1. We provide the definition of AC_DEFINE_DIR ourselves in
   gdb/acinclude.m4, so what I said earlier about the fix having to be
   in Autoconf was wrong. Too bad, it's always a relief when the blame
   lies somewhere else. :-)

2. We can do the escape trick above automatically in gdb/configure.ac.

So I just sent a patch to do that:

https://inbox.sourceware.org/gdb-patches/20231026234013.937210-1-thiago.bauermann@linaro.org/

> I've updated the Bugzilla bug with this information.

Thanks. I will also update the bugzilla with my findings.
  

> From: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
> Cc: gdb-patches@sourceware.org, tom@tromey.com
> Date: Thu, 26 Oct 2023 20:48:58 -0300
> 
> > FTR: just tried this with the gdb-14.0.91 pretest, and it works just
> > fine.  Thank you very much for helping me avoid this annoying problem
> > (it previously required me to build GDB twice).
> 
> Excellent! I poked at it some more today and I noticed two things:
> 
> 1. We provide the definition of AC_DEFINE_DIR ourselves in
>    gdb/acinclude.m4, so what I said earlier about the fix having to be
>    in Autoconf was wrong. Too bad, it's always a relief when the blame
>    lies somewhere else. :-)
> 
> 2. We can do the escape trick above automatically in gdb/configure.ac.
> 
> So I just sent a patch to do that:
> 
> https://inbox.sourceware.org/gdb-patches/20231026234013.937210-1-thiago.bauermann@linaro.org/

Thanks, this is even better!