[PING][PATCH] [gdb/exp] Limit workaround in using_direct::valid_line to broken GCC versions

[Tom de Vries <tdevries@suse.de>]

On 6/4/26 6:21 PM, Tom de Vries wrote:
> Consider test.c:
> ...
>       1	namespace mod_a {
>       2	  int xxx = 10;
>       3	}
>       4
>       5	static void
>       6	foo ()
>       7	{
>       8	}
>       9
>      10	int
>      11	main ()
>      12	{
>      13	  {
>      14	    foo ();
>      15	    using namespace mod_a;
>      16	  }
>      17
>      18	  return mod_a::xxx;
>      19	}
> ...
> compiled with "g++ test.c -g".
> 
> Attempting to print xxx at line 14 shouldn't find anything (because it's
> before the "using namespace mod_a"), but it does:
> ...
> $ gdb -q -batch a.out -ex start -ex "p xxx"
> ...
> Temporary breakpoint 1, main () at test.c:14
> 14	    foo ();
> $1 = 10
> ...
> 
> This happens because using_direct::valid_line returns true here:
> ...
>        return (decl_line <= curr_sal.line)
> 	     || (decl_line >= boundary);
> ...
> 
> Since we have decl_line == 15 and curr_sal.line == 14,
> "(decl_line <= curr_sal.line)" evaluates to false.
> 
> But boundary == 14, so "(decl_line >= boundary)" evaluates to true.
> 
> The "(decl_line >= boundary)" bit was added as a workaround for
> GCC PR debug/108716.
> 
> Since I'm using GCC 15, the workaround is not needed.
> 
> Fix this by limiting the workaround to broken GCC versions.
> 

Ping.

Thanks,
- Tom

> Tested on x86_64-linux, using GCC 15.2, and 7.5.
> 
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=34203
> ---
>   gdb/cp-namespace.c                       | 26 +++++++++++---
>   gdb/namespace.c                          |  9 +++--
>   gdb/testsuite/gdb.cp/ns-before-using.c   | 37 ++++++++++++++++++++
>   gdb/testsuite/gdb.cp/ns-before-using.exp | 44 ++++++++++++++++++++++++
>   4 files changed, 110 insertions(+), 6 deletions(-)
>   create mode 100644 gdb/testsuite/gdb.cp/ns-before-using.c
>   create mode 100644 gdb/testsuite/gdb.cp/ns-before-using.exp
> 
> diff --git a/gdb/cp-namespace.c b/gdb/cp-namespace.c
> index c8cd5c245aa..16fd4e2ded8 100644
> --- a/gdb/cp-namespace.c
> +++ b/gdb/cp-namespace.c
> @@ -33,6 +33,7 @@
>   #include "namespace.h"
>   #include "inferior.h"
>   #include "gdbsupport/unordered_map.h"
> +#include "producer.h"
>   #include <string>
>   #include <string.h>
>   
> @@ -410,9 +411,26 @@ cp_lookup_symbol_via_imports (const char *scope,
>   	found_symbols[sym.symbol->m_name] = sym;
>       }
>   
> -  /* Due to a GCC bug, we need to know the boundaries of the current block
> -     to know if a certain using directive is valid.  */
> -  symtab_and_line boundary_sal = find_sal_for_pc (block->end () - 1, 0);
> +  unsigned boundary_line = 0;
> +  {
> +    struct symbol *fn = block->containing_function ();
> +    int major, minor;
> +    if (fn != nullptr
> +	&& producer_is_gcc (fn->symtab ()->compunit ()->producer (),
> +			    &major, &minor)
> +	&& (major <= 9
> +	    || (major == 10 && minor < 5)
> +	    || (major == 11 && minor < 4)
> +	    || (major == 12 && minor < 3)
> +	    || (major == 13 && minor < 1)))
> +      {
> +	/* Due to a GCC bug (PR debug/108716, fixed in 10.5, 11.4, 12.3, 13.1),
> +	   we need to know the boundaries of the current block to know if a
> +	   certain using directive is valid.  */
> +	symtab_and_line boundary_sal = find_sal_for_pc (block->end () - 1, 0);
> +	boundary_line = boundary_sal.line;
> +      }
> +  }
>   
>     /* Go through the using directives.  If any of them add new names to
>        the namespace we're searching in, see if we can find a match by
> @@ -423,7 +441,7 @@ cp_lookup_symbol_via_imports (const char *scope,
>   
>         /* If the using directive was below the place we are stopped at,
>   	 do not use this directive.  */
> -      if (!current->valid_line (boundary_sal.line))
> +      if (!current->valid_line (boundary_line))
>   	continue;
>         len = strlen (current->import_dest);
>         directive_match = (search_parents
> diff --git a/gdb/namespace.c b/gdb/namespace.c
> index 5b5749369ee..d81365a284a 100644
> --- a/gdb/namespace.c
> +++ b/gdb/namespace.c
> @@ -113,8 +113,13 @@ using_direct::valid_line (unsigned int boundary) const
>       {
>         CORE_ADDR curr_pc = get_frame_pc (get_selected_frame (nullptr));
>         symtab_and_line curr_sal = find_sal_for_pc (curr_pc, 0);
> -      return (decl_line <= curr_sal.line)
> -	     || (decl_line >= boundary);
> +
> +      /* Apply GCC PR debug/108716 workaround.  */
> +      if (boundary != 0
> +	  && decl_line >= boundary)
> +	return true;
> +
> +      return decl_line <= curr_sal.line;
>       }
>     catch (const gdb_exception &ex)
>       {
> diff --git a/gdb/testsuite/gdb.cp/ns-before-using.c b/gdb/testsuite/gdb.cp/ns-before-using.c
> new file mode 100644
> index 00000000000..f74c35b0d3f
> --- /dev/null
> +++ b/gdb/testsuite/gdb.cp/ns-before-using.c
> @@ -0,0 +1,37 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   Copyright 2026 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/>.  */
> +
> +namespace mod_a
> +{
> +  int xxx = 10;
> +}
> +
> +static void
> +foo ()
> +{
> +}
> +
> +int
> +main ()
> +{
> +  {
> +    foo ();
> +    using namespace mod_a;
> +  }
> +
> +  return mod_a::xxx;
> +}
> diff --git a/gdb/testsuite/gdb.cp/ns-before-using.exp b/gdb/testsuite/gdb.cp/ns-before-using.exp
> new file mode 100644
> index 00000000000..f891cf56c49
> --- /dev/null
> +++ b/gdb/testsuite/gdb.cp/ns-before-using.exp
> @@ -0,0 +1,44 @@
> +# Copyright 2026 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/>.
> +
> +standard_testfile .c
> +
> +if {[prepare_for_testing "failed to prepare" $testfile $srcfile \
> +	 {debug c++}]} {
> +    return
> +}
> +
> +if {![runto_main]} {
> +    continue
> +}
> +
> +# Xfail for incorrect decl_line on DW_TAG_imported_module,
> +# GCC PR debug/108716.
> +set have_gcc108716_xfail \
> +    [expr {[test_compiler_info gcc-*] && [gcc_major_version] < 13}]
> +
> +# Regression test for PR exp/34203.
> +set re_pass [string_to_regexp {No symbol "xxx" in current context.}]
> +gdb_test_multiple "print xxx" "" {
> +    -re -wrap $re_pass {
> +	pass $gdb_test_name
> +    }
> +    -re -wrap "$valnum_re = 10" {
> +	if {$have_gcc108716_xfail} {
> +	    setup_xfail *-*-* gcc/108716
> +	}
> +	fail $gdb_test_name
> +    }
> +}
> 
> base-commit: bd64797371d27c766d551d0bf115d9090f1d0594