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

Tom de Vries via Gdb-patches
2023-08-29T17:59:26Z

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On 8/29/23 18:03, Kevin Buettner wrote:
> 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
>

Hi Kevin,

thanks for the review.

I'll commit this v2 tomorrow, unless there are further comments.

Thanks,
- Tom

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From abd9eb3248fa506965d75fd3caa60fcc63e8b8f0 Mon Sep 17 00:00:00 2001
From: Tom de Vries <tdevries@suse.de>
Date: Tue, 29 Aug 2023 17:29:17 +0200
Subject: [PATCH] [gdb/build] Fix C inclusion of nat/x86-cpuid.h

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

=== gdb Summary ===

# of untested testcases 1
...

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.

Tested on x86_64-linux.

Co-Authored-By: Kevin Buettner <kevinb@redhat.com>
---
gdb/nat/x86-cpuid.h | 12 ++++++++++++
1 file changed, 12 insertions(+)

diff --git a/gdb/nat/x86-cpuid.h b/gdb/nat/x86-cpuid.h
index 517113d45e8..e1b0321d593 100644
--- a/gdb/nat/x86-cpuid.h
+++ b/gdb/nat/x86-cpuid.h
@@ -22,6 +22,12 @@
/* Always include the header for the cpu bit defines. */
#include "x86-gcc-cpuid.h"

+#ifndef __cplusplus
+/* This header file is also used in C code for some test-cases, so define
+ nullptr in C terms to avoid a compilation error. */
+#define nullptr ((void *) 0)
+#endif
+
#if defined(__i386__) || defined(__x86_64__)

/* Return cpuid data for requested cpuid level, as found in returned
@@ -92,4 +98,10 @@ x86_cpuid_count (unsigned int __level, unsigned int __sublevel,

#endif /* i386 && x86_64 */

+#ifndef __cplusplus
+/* Avoid leaking this local definition beyond the scope of this header
+ file. */
+#undef nullptr
+#endif
+
#endif /* NAT_X86_CPUID_H */

base-commit: 8468e03688622f265529699e2efd355a4c122cc6
--
2.35.3