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

[Lancelot SIX <lsix@lancelotsix.com>]

Hi Kevin,

On Thu, Sep 21, 2023 at 06:22:12PM -0700, Kevin Buettner via Gdb-patches wrote:
> 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.
> 
> Co-Authored-by: Jan Kratochvil <jan@jankratochvil.net>
> ---
>  gdb/testsuite/gdb.threads/tls-sepdebug-main.c | 27 ++++++
>  .../gdb.threads/tls-sepdebug-shared.c         | 18 ++++
>  gdb/testsuite/gdb.threads/tls-sepdebug.exp    | 86 +++++++++++++++++++
>  3 files changed, 131 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
> 
> diff --git a/gdb/testsuite/gdb.threads/tls-sepdebug-main.c b/gdb/testsuite/gdb.threads/tls-sepdebug-main.c
> new file mode 100644
> index 00000000000..97b5bf5ae0e
> --- /dev/null
> +++ b/gdb/testsuite/gdb.threads/tls-sepdebug-main.c
> @@ -0,0 +1,27 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   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/>.  */
> +
> +#include <pthread.h>
> +
> +extern __thread int var;

I think you could replace __thread (a GCC extension) with thread_local
which was introduced in C11 (available in the <threads.h> header)[1].

This could require adding -std=c11 to additional_flags in the .exp file
(not sure which C standard is picked by default by different versions of
GCC).

[1] https://en.cppreference.com/w/c/thread/thread_local

Best,
Lancelot.

> +
> +int main()
> +{
> +  /* Ensure we link against pthreads even with --as-needed.  */
> +  pthread_testcancel();
> +  return var;
> +}
> diff --git a/gdb/testsuite/gdb.threads/tls-sepdebug-shared.c b/gdb/testsuite/gdb.threads/tls-sepdebug-shared.c
> new file mode 100644
> index 00000000000..c63515f3011
> --- /dev/null
> +++ b/gdb/testsuite/gdb.threads/tls-sepdebug-shared.c
> @@ -0,0 +1,18 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   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/>.  */
> +
> +__thread int var = 42;
> diff --git a/gdb/testsuite/gdb.threads/tls-sepdebug.exp b/gdb/testsuite/gdb.threads/tls-sepdebug.exp
> new file mode 100644
> index 00000000000..df4fccee567
> --- /dev/null
> +++ b/gdb/testsuite/gdb.threads/tls-sepdebug.exp
> @@ -0,0 +1,86 @@
> +# 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
> +
> +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 ${binmainfile}
> +# making LD_LIBRARY_PATH tests useless.
> +if  { [gdb_compile_shlib \
> +	"${srcdir}/${subdir}/${srcsharedfile}" "${binsharedfile}" \
> +	[list debug additional_flags=-Wl,-soname=${binsharedbase}]] != "" } {
> +    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 {debug}] != "" } {
> +    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 = \[0-9\].*" \
> +		 "print TLS variable from a shared library with separate debug info file"
> +    }
> +}
> -- 
> 2.41.0
>