Re: [PATCH] [gdb/build] Work around GCC ipa-modref bug

[Sam James <sam@gentoo.org>]

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

> PR mi/32571 reports the following problem:
> ...
> $ gdb -q -batch -ex "b bla.c:100"
> <random output>
> Make breakpoint pending on future shared library load? (y or [n]) \
>   [answered N; input not from terminal]
> ...
> while this is expected:
> ...
> $ gdb -q -batch -ex "b bla.c:100"
> No symbol table is loaded.  Use the "file" command.
> Make breakpoint pending on future shared library load? (y or [n]) \
>   [answered N; input not from terminal]
> ...
>
> A few factors in reproducing this are building gdb using gcc 14,
> "-O2 -flto=auto" and --disable-nls.  For more details, see the PR.
>
> This turns out to be caused by a GCC PR [1], more specifically a problem in
> ipa-modref.
>
> Work around this by disabling ipa-modref for GCC versions 12-15 and 16.0,
> assuming the GCC 16.1 release will contain a fix.
>
> Tested on aarch64-linux and x86_64-linux.
>
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=32571
>
> [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120987
> ---
>  gdbsupport/common-defs.h | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/gdbsupport/common-defs.h b/gdbsupport/common-defs.h
> index 07caf3bd7e4..bdf04d9ec09 100644
> --- a/gdbsupport/common-defs.h
> +++ b/gdbsupport/common-defs.h
> @@ -27,6 +27,14 @@
>  #pragma GCC optimize("-fno-hoist-adjacent-loads")
>  #endif
>  
> +#if defined (__GNUC__) && !defined (__clang__) \
> +  && ((__GNUC__ >= 12 && __GNUC__ <= 15)       \
> +      || (__GNUC__ == 16 && __GNUC_MINOR__ < 1))
> +/* Work around PR gcc/110799 starting gcc 12, and assume it will be fixed in
> +   the gcc 16.1 release.  */
> +#pragma GCC optimize("-fno-ipa-modref")
> +#endif
> +
>  #include <gdbsupport/config.h>
>  
>  #undef PACKAGE_NAME
>
> base-commit: 6ab3f09a682adcb4e841faf7fc19dea2671debed

LGTM. Thanks for reducing it and digging into this.