* [PATCH] gdbsupport: include cstdlib in common-defs.h
@ 2020-04-09 22:50 Simon Marchi
2020-04-09 23:34 ` Christian Biesinger
0 siblings, 1 reply; 5+ messages in thread
From: Simon Marchi @ 2020-04-09 22:50 UTC (permalink / raw)
To: gdb-patches; +Cc: Alexey Brodkin, Simon Marchi
In PR 25731 [1], the following build failure was reported:
../../binutils-gdb/gdb/gdbtypes.c:1254:10: error: no member named 'abs' in namespace 'std'; did you mean simply 'abs'?
= ((std::abs (stride) * element_count) + 7) / 8;
^~~~~~~~
abs
/usr/include/stdlib.h:129:6: note: 'abs' declared here
int abs(int) __pure2;
^
The original report was using:
$ gcc -v
Apple LLVM version 8.0.0 (clang-800.0.42.1)
Target: x86_64-apple-darwin15.6.0
Note that I was _not_ able to reproduce using:
$ g++ --version
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/4.2.1
Apple clang version 11.0.0 (clang-1100.0.33.17)
Target: x86_64-apple-darwin19.3.0
The proposed fix is to include <cstdlib> in addition to <stdlib.h>.
Here's an excerpt of [2] relevant to this problem:
These headers [speaking of the .h form] are allowed to also declare
the same names in the std namespace, and the corresponding cxxx
headers are allowed to also declare the same names in the global
namespace: including <cstdlib> definitely provides std::malloc and
may also provide ::malloc. Including <stdlib.h> definitely provides
::malloc and may also provide std::malloc
Since we use std::abs, we should not assume that our include of stdlib.h
declares an `abs` function in the `std` namespace.
If we replace the include of stdlib.h with cstdlib, then we fall in the
opposite situation. A standard C++ library may decide to only put the
declarations in the std namespace, requiring us to prefix all standard
functions with `std::`. I'm not against that, but for the moment I think the
safest way forward is to just include both.
Note that I don't know what effect this patch can have on any stdlib.h fix
provided by gnulib.
[1] https://sourceware.org/bugzilla/show_bug.cgi?id=25731
[2] https://en.cppreference.com/w/cpp/header#C_compatibility_headers
gdbsupport/ChangeLog:
* common-defs.h: Include cstdlib.h.
---
gdbsupport/common-defs.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/gdbsupport/common-defs.h b/gdbsupport/common-defs.h
index e42d2b80c045..257b6279b888 100644
--- a/gdbsupport/common-defs.h
+++ b/gdbsupport/common-defs.h
@@ -84,6 +84,7 @@
#include <stdarg.h>
#include <stdio.h>
+#include <cstdlib>
#include <stdlib.h>
#include <stddef.h>
#include <stdint.h>
--
2.26.0
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] gdbsupport: include cstdlib in common-defs.h
2020-04-09 22:50 [PATCH] gdbsupport: include cstdlib in common-defs.h Simon Marchi
@ 2020-04-09 23:34 ` Christian Biesinger
2020-04-10 14:39 ` Simon Marchi
0 siblings, 1 reply; 5+ messages in thread
From: Christian Biesinger @ 2020-04-09 23:34 UTC (permalink / raw)
To: Simon Marchi; +Cc: gdb-patches, Alexey Brodkin
On Thu, Apr 9, 2020 at 5:50 PM Simon Marchi via Gdb-patches
<gdb-patches@sourceware.org> wrote:
>
> In PR 25731 [1], the following build failure was reported:
>
> ../../binutils-gdb/gdb/gdbtypes.c:1254:10: error: no member named 'abs' in namespace 'std'; did you mean simply 'abs'?
> = ((std::abs (stride) * element_count) + 7) / 8;
> ^~~~~~~~
> abs
> /usr/include/stdlib.h:129:6: note: 'abs' declared here
> int abs(int) __pure2;
> ^
> The original report was using:
>
> $ gcc -v
> Apple LLVM version 8.0.0 (clang-800.0.42.1)
> Target: x86_64-apple-darwin15.6.0
>
> Note that I was _not_ able to reproduce using:
>
> $ g++ --version
> Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/4.2.1
> Apple clang version 11.0.0 (clang-1100.0.33.17)
> Target: x86_64-apple-darwin19.3.0
>
> The proposed fix is to include <cstdlib> in addition to <stdlib.h>.
>
> Here's an excerpt of [2] relevant to this problem:
>
> These headers [speaking of the .h form] are allowed to also declare
> the same names in the std namespace, and the corresponding cxxx
> headers are allowed to also declare the same names in the global
> namespace: including <cstdlib> definitely provides std::malloc and
> may also provide ::malloc. Including <stdlib.h> definitely provides
> ::malloc and may also provide std::malloc
>
> Since we use std::abs, we should not assume that our include of stdlib.h
> declares an `abs` function in the `std` namespace.
>
> If we replace the include of stdlib.h with cstdlib, then we fall in the
> opposite situation. A standard C++ library may decide to only put the
> declarations in the std namespace, requiring us to prefix all standard
> functions with `std::`. I'm not against that, but for the moment I think the
> safest way forward is to just include both.
>
> Note that I don't know what effect this patch can have on any stdlib.h fix
> provided by gnulib.
>
> [1] https://sourceware.org/bugzilla/show_bug.cgi?id=25731
> [2] https://en.cppreference.com/w/cpp/header#C_compatibility_headers
>
> gdbsupport/ChangeLog:
>
> * common-defs.h: Include cstdlib.h.
> ---
> gdbsupport/common-defs.h | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/gdbsupport/common-defs.h b/gdbsupport/common-defs.h
> index e42d2b80c045..257b6279b888 100644
> --- a/gdbsupport/common-defs.h
> +++ b/gdbsupport/common-defs.h
> @@ -84,6 +84,7 @@
>
> #include <stdarg.h>
> #include <stdio.h>
> +#include <cstdlib>
> #include <stdlib.h>
> #include <stddef.h>
> #include <stdint.h>
I think this is reasonable, but I would add a comment why both cstdlib
and stdlib.h are included (ie. to get the std:: version with
overloaded functions)
Christian
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] gdbsupport: include cstdlib in common-defs.h
2020-04-09 23:34 ` Christian Biesinger
@ 2020-04-10 14:39 ` Simon Marchi
2020-04-10 17:29 ` Christian Biesinger
0 siblings, 1 reply; 5+ messages in thread
From: Simon Marchi @ 2020-04-10 14:39 UTC (permalink / raw)
To: Christian Biesinger; +Cc: gdb-patches, Alexey Brodkin
On 2020-04-09 7:34 p.m., Christian Biesinger wrote:
> I think this is reasonable, but I would add a comment why both cstdlib
> and stdlib.h are included (ie. to get the std:: version with
> overloaded functions)
A comment would certainly be useful. Does that sound right?
/* Include both stdlib.h and cstdlib to make sure to get the standard C
functions in the global namespace and the overloads in the std
namespace. */
Simon
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] gdbsupport: include cstdlib in common-defs.h
2020-04-10 14:39 ` Simon Marchi
@ 2020-04-10 17:29 ` Christian Biesinger
2020-04-27 13:30 ` Simon Marchi
0 siblings, 1 reply; 5+ messages in thread
From: Christian Biesinger @ 2020-04-10 17:29 UTC (permalink / raw)
To: Simon Marchi; +Cc: gdb-patches, Alexey Brodkin
On Fri, Apr 10, 2020 at 9:40 AM Simon Marchi <simon.marchi@polymtl.ca> wrote:
>
> On 2020-04-09 7:34 p.m., Christian Biesinger wrote:
> > I think this is reasonable, but I would add a comment why both cstdlib
> > and stdlib.h are included (ie. to get the std:: version with
> > overloaded functions)
>
> A comment would certainly be useful. Does that sound right?
>
> /* Include both stdlib.h and cstdlib to make sure to get the standard C
> functions in the global namespace and the overloads in the std
> namespace. */
That sounds good to me.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] gdbsupport: include cstdlib in common-defs.h
2020-04-10 17:29 ` Christian Biesinger
@ 2020-04-27 13:30 ` Simon Marchi
0 siblings, 0 replies; 5+ messages in thread
From: Simon Marchi @ 2020-04-27 13:30 UTC (permalink / raw)
To: Christian Biesinger; +Cc: gdb-patches, Alexey Brodkin
On 2020-04-10 1:29 p.m., Christian Biesinger wrote:
> On Fri, Apr 10, 2020 at 9:40 AM Simon Marchi <simon.marchi@polymtl.ca> wrote:
>>
>> On 2020-04-09 7:34 p.m., Christian Biesinger wrote:
>>> I think this is reasonable, but I would add a comment why both cstdlib
>>> and stdlib.h are included (ie. to get the std:: version with
>>> overloaded functions)
>>
>> A comment would certainly be useful. Does that sound right?
>>
>> /* Include both stdlib.h and cstdlib to make sure to get the standard C
>> functions in the global namespace and the overloads in the std
>> namespace. */
>
> That sounds good to me.
>
I pushed this patch, although with a slightly different comment, because I forgot
I had written one here. But it says essentially the same thing.
Simon
^ permalink raw reply [flat|nested] 5+ messages in thread
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2020-04-09 22:50 [PATCH] gdbsupport: include cstdlib in common-defs.h Simon Marchi
2020-04-09 23:34 ` Christian Biesinger
2020-04-10 14:39 ` Simon Marchi
2020-04-10 17:29 ` Christian Biesinger
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