Re: [PATCH] testsuite: ada-valprint-error relocation issue

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

On 4/1/26 4:10 PM, Bratislav Filipovic wrote:
> The ada-valprint-error.exp test links a nodebug .o file with a separate
> DWARF .o file generated by lib/dwarf.exp. This requires the linker to
> apply relocations for initialized pointers in the .data section.
> 
> Some clang + linker combinations fail to apply these relocations,
> leaving fd__global as NULL instead of pointing to buffer. This causes
> the test to print null instead of the expected error message.
> 
> Binary evidence from .comment section confirms which compiler and
> linker were used. Testing shows:
> - GCC 13 + GNU ld 2.42: PASS
> - clang 20 + GNU ld 2.42: FAIL
> - clang 22 + ld.lld 22: FAIL
> - clang 17/19 + GNU ld 2.45.0: PASS
> 
> The failure is a linker limitation when handling this specific
> relocation pattern, not a GDB bug. Document this in the test file
> to help users understand why the test may fail with certain toolchains.

Hi,

the patch LGTM, but I'm wondering, do you have a copyright assignment, 
or are you covered by an AMD blanket assignment perhaps?

Thanks,
- Tom

> ---
>   .../gdb.dwarf2/ada-valprint-error.exp         | 21 +++++++++++++++++++
>   1 file changed, 21 insertions(+)
> 
> diff --git a/gdb/testsuite/gdb.dwarf2/ada-valprint-error.exp b/gdb/testsuite/gdb.dwarf2/ada-valprint-error.exp
> index f3d61e91..00e737bc 100644
> --- a/gdb/testsuite/gdb.dwarf2/ada-valprint-error.exp
> +++ b/gdb/testsuite/gdb.dwarf2/ada-valprint-error.exp
> @@ -107,6 +107,27 @@ if { [prepare_for_testing ${testfile}.exp ${testfile} \
>       return -1
>   }
>   
> +# Note: This test may fail with certain clang + linker combinations
> +# Specifically, clang + ld.lld can fail to apply relocations when linking
> +# nodebug .o with separate DWARF .o, leaving fd__global as NULL instead
> +# of pointing to buffer. The failure is a linker limitation, not a GDB bug.
> +#
> +# Known to fail: clang 20/22 + GNU ld 2.42, clang 22 + ld.lld 22
> +# Known to pass: GCC + GNU ld, clang 17/19 + GNU ld 2.45.0
> +set unsupported 0
> +gdb_test_multiple "print /x fd__global" "check fd__global value" {
> +    -re -wrap "@0x0: 0x0" {
> +	set unsupported 1
> +    }
> +    -re -wrap "" {
> +	pass $gdb_test_name
> +    }
> +}
> +if {$unsupported} {
> +    unsupported "linker failed to apply relocation for fd__global"
> +    return
> +}
> +
>   gdb_test_no_output "set language ada"
>   
>   gdb_test "print fd.global" \