Re: [PATCH] [gdb/build] Fix C inclusion of nat/x86-cpuid.h

[Kevin Buettner via Gdb-patches <gdb-patches@sourceware.org>]

On Tue, 29 Aug 2023 17:38:57 +0200
Tom de Vries via Gdb-patches <gdb-patches@sourceware.org> wrote:

> When running test-case gdb.arch/i386-avx512.exp, I run into:
> ...
>  gdb compile failed, In file included from gdb.arch/i386-avx512.c:20:0:
>  src/gdb/nat/x86-cpuid.h: In function 'x86_cpuid_count':
>  src/gdb/nat/x86-cpuid.h:63:16: error: \
>    'nullptr' undeclared (first use in this function)
>     if (__eax == nullptr)
>                  ^~~~~~~
>  src/gdb/nat/x86-cpuid.h:63:16: note: each \
>    undeclared identifier is reported only once for each function it appears in
[...]
> This is due to commit e85aad4ae76 ("nat/x86-cpuid.h: Add x86_cpuid_count
> wrapper around __get_cpuid_count"), which introduced the nullptr check.
> 
> The header file gdb/nat/x86-cpuid.h is a file that is included in the build
> and compiled as a C++ file, but also in the testsuite and compiled as a C
> file.
> 
> Fix this by replacing nullptr with (void *)0.
[...]

> -  if (__eax == nullptr)
> +  if (__eax == (void *)0)
>      __eax = &__scratch;
> -  if (__ebx == nullptr)
> +  if (__ebx == (void *)0)
>      __ebx = &__scratch;
> -  if (__ecx == nullptr)
> +  if (__ecx == (void *)0)
>      __ecx = &__scratch;
> -  if (__edx == nullptr)
> +  if (__edx == (void *)0)
>      __edx = &__scratch;

Maybe leave nullptr in place and instead do something like this...

/* This header file is also used in C code for the gdb.arch/i386-avx512.exp
   test, so define nullptr to avoid a compile error during testing.  */
#ifndef __cplusplus
#define nullptr (void *) 0)
#endif

Kevin