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

[Tom de Vries via Gdb-patches <gdb-patches@sourceware.org>]

[-- Attachment #1: Type: text/plain, Size: 1795 bytes --]

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


[-- Attachment #2: 0001-gdb-build-Fix-C-inclusion-of-nat-x86-cpuid.h.patch --]
[-- Type: text/x-patch, Size: 2169 bytes --]

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