On Tue, Oct 13, 2015 at 2:12 PM, Eric Fiselier via cfe-commits <
cfe-commits@lists.llvm.org> wrote:
> I would rather not do this if possible but I understand why we need to do
> it.
>
> Richard is there a cost associated with the 'extern "C++"' construct? or
> by forcing the compiler to switch modes in general?
>
Not a significant one compared to the cost of the code wrapped in the
'extern "C++"' here. (Also, this is wrapped in an #ifdef that only applies
in C++98; we could further reduce the set of cases when this happens by
using _Static_assert when available instead of this static_assert
emulation.)
> On Mon, Oct 12, 2015 at 12:27 PM, Richard Smith <rich...@metafoo.co.uk>
> wrote:
>
>> On Mon, Oct 12, 2015 at 9:41 AM, Steven Wu via cfe-commits <
>> cfe-commits@lists.llvm.org> wrote:
>>
>>> Hi Richard
>>>
>>> Your splitting seems causing problem when using extern "C". Here is a
>>> test case:
>>>
>>> $ cat test.cpp
>>> #ifdef __cplusplus
>>> extern "C" {
>>> #endif
>>> #include <stdio.h>
>>> #ifdef __cplusplus
>>> }
>>> #endif
>>>
>>> Error:
>>> clang -fsyntax-only test.cpp
>>> In file included from test.cpp:4:
>>> In file included from /usr/bin/../include/c++/v1/stdio.h:102:
>>> /usr/bin/../include/c++/v1/__config:593:1: error:
>>> templates must have C++ linkage
>>> template <bool> struct __static_assert_test;
>>> ^~~~~~~~~~~~~~~
>>> /usr/bin/../include/c++/v1/__config:594:20: error:
>>> explicit specialization of non-template struct
>>> '__static_assert_test'
>>> template <> struct __static_assert_test<true> {};
>>> ^ ~~~~~~
>>> /usr/bin/../include/c++/v1/__config:595:1: error:
>>> templates must have C++ linkage
>>> template <unsigned> struct __static_assert_check {};
>>> ^~~~~~~~~~~~~~~~~~~
>>> 3 errors generated.
>>>
>>> Because the code is actually compiled in C++, the guard in the header
>>> failed to exclude the templates. In the meantime, I don't know if there are
>>> ways to detect the header is in extern "C".
>>>
>>
>> This was supposed to work, but apparently I only tested it when compiling
>> as C++11; the static_assert emulation in C++98 mode needs some massaging to
>> cope with this.
>>
>> Eric, Marshall: Are you OK with the attached patch? The idea is to make
>> <__config> be fine to include in extern "C" or extern "C++" modes (and
>> likewise for the <foo.h> headers). This is something that comes up pretty
>> often in practice (people wrap an include of a C header in 'extern "C"',
>> and that C header includes a <foo.h> file that libc++ provides).
>>
>>
>>> Steven
>>>
>>>
>>> > On Oct 8, 2015, at 6:29 PM, Richard Smith via cfe-commits <
>>> cfe-commits@lists.llvm.org> wrote:
>>> >
>>> > Author: rsmith
>>> > Date: Thu Oct 8 20:29:09 2015
>>> > New Revision: 249798
>>> >
>>> > URL: http://llvm.org/viewvc/llvm-project?rev=249798&view=rev
>>> > Log:
>>> > Split <stdio.h> out of <cstdio>.
>>> >
>>> > As with <stddef.h>, skip our custom header if __need_FILE or
>>> __need___FILE is defined.
>>> >
>>> > Added:
>>> > libcxx/trunk/include/stdio.h
>>> > - copied, changed from r249736, libcxx/trunk/include/cstdio
>>> > Modified:
>>> > libcxx/trunk/include/cstdio
>>> > libcxx/trunk/test/std/depr/depr.c.headers/stdio_h.pass.cpp
>>> >
>>> > Modified: libcxx/trunk/include/cstdio
>>> > URL:
>>> http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/cstdio?rev=249798&r1=249797&r2=249798&view=diff
>>> >
>>> ==============================================================================
>>> > --- libcxx/trunk/include/cstdio (original)
>>> > +++ libcxx/trunk/include/cstdio Thu Oct 8 20:29:09 2015
>>> > @@ -103,16 +103,6 @@ void perror(const char* s);
>>> > #pragma GCC system_header
>>> > #endif
>>> >
>>> > -// snprintf
>>> > -#if defined(_LIBCPP_MSVCRT)
>>> > -#include "support/win32/support.h"
>>> > -#endif
>>> > -
>>> > -#undef getc
>>> > -#undef putc
>>> > -#undef clearerr
>>> > -#undef feof
>>> > -#undef ferror
>>> > _LIBCPP_BEGIN_NAMESPACE_STD
>>> >
>>> > using ::FILE;
>>> >
>>> > Copied: libcxx/trunk/include/stdio.h (from r249736,
>>> libcxx/trunk/include/cstdio)
>>> > URL:
>>> http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/stdio.h?p2=libcxx/trunk/include/stdio.h&p1=libcxx/trunk/include/cstdio&r1=249736&r2=249798&rev=249798&view=diff
>>> >
>>> ==============================================================================
>>> > --- libcxx/trunk/include/cstdio (original)
>>> > +++ libcxx/trunk/include/stdio.h Thu Oct 8 20:29:09 2015
>>> > @@ -1,5 +1,5 @@
>>> > // -*- C++ -*-
>>> > -//===---------------------------- cstdio
>>> ----------------------------------===//
>>> > +//===---------------------------- stdio.h
>>> ---------------------------------===//
>>> > //
>>> > // The LLVM Compiler Infrastructure
>>> > //
>>> > @@ -8,11 +8,19 @@
>>> > //
>>> >
>>> //===----------------------------------------------------------------------===//
>>> >
>>> > -#ifndef _LIBCPP_CSTDIO
>>> > -#define _LIBCPP_CSTDIO
>>> > +#if defined(__need_FILE) || defined(__need___FILE)
>>> > +
>>> > +#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
>>> > +#pragma GCC system_header
>>> > +#endif
>>> > +
>>> > +#include_next <stdio.h>
>>> > +
>>> > +#elif !defined(_LIBCPP_STDIO_H)
>>> > +#define _LIBCPP_STDIO_H
>>> >
>>> > /*
>>> > - cstdio synopsis
>>> > + stdio.h synopsis
>>> >
>>> > Macros:
>>> >
>>> > @@ -33,9 +41,6 @@ Macros:
>>> > stdin
>>> > stdout
>>> >
>>> > -namespace std
>>> > -{
>>> > -
>>> > Types:
>>> >
>>> > FILE
>>> > @@ -92,20 +97,23 @@ void clearerr(FILE* stream);
>>> > int feof(FILE* stream);
>>> > int ferror(FILE* stream);
>>> > void perror(const char* s);
>>> > -
>>> > -} // std
>>> > */
>>> >
>>> > #include <__config>
>>> > -#include <stdio.h>
>>> >
>>> > #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
>>> > #pragma GCC system_header
>>> > #endif
>>> >
>>> > +#include_next <stdio.h>
>>> > +
>>> > +#ifdef __cplusplus
>>> > +
>>> > // snprintf
>>> > #if defined(_LIBCPP_MSVCRT)
>>> > +extern "C++" {
>>> > #include "support/win32/support.h"
>>> > +}
>>> > #endif
>>> >
>>> > #undef getc
>>> > @@ -113,72 +121,7 @@ void perror(const char* s);
>>> > #undef clearerr
>>> > #undef feof
>>> > #undef ferror
>>> > -_LIBCPP_BEGIN_NAMESPACE_STD
>>> > -
>>> > -using ::FILE;
>>> > -using ::fpos_t;
>>> > -using ::size_t;
>>> > -
>>> > -using ::fclose;
>>> > -using ::fflush;
>>> > -using ::setbuf;
>>> > -using ::setvbuf;
>>> > -using ::fprintf;
>>> > -using ::fscanf;
>>> > -using ::snprintf;
>>> > -using ::sprintf;
>>> > -using ::sscanf;
>>> > -#ifndef _LIBCPP_MSVCRT
>>> > -using ::vfprintf;
>>> > -using ::vfscanf;
>>> > -using ::vsscanf;
>>> > -#endif // _LIBCPP_MSVCRT
>>> > -using ::vsnprintf;
>>> > -using ::vsprintf;
>>> > -using ::fgetc;
>>> > -using ::fgets;
>>> > -using ::fputc;
>>> > -using ::fputs;
>>> > -using ::getc;
>>> > -using ::putc;
>>> > -using ::ungetc;
>>> > -using ::fread;
>>> > -using ::fwrite;
>>> > -using ::fgetpos;
>>> > -using ::fseek;
>>> > -using ::fsetpos;
>>> > -using ::ftell;
>>> > -using ::rewind;
>>> > -using ::clearerr;
>>> > -using ::feof;
>>> > -using ::ferror;
>>> > -using ::perror;
>>> > -
>>> > -#ifndef _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
>>> > -using ::fopen;
>>> > -using ::freopen;
>>> > -using ::remove;
>>> > -using ::rename;
>>> > -using ::tmpfile;
>>> > -using ::tmpnam;
>>> > -#endif
>>> >
>>> > -#ifndef _LIBCPP_HAS_NO_STDIN
>>> > -using ::getchar;
>>> > -#if _LIBCPP_STD_VER <= 11
>>> > -using ::gets;
>>> > #endif
>>> > -using ::scanf;
>>> > -using ::vscanf;
>>> > -#endif
>>> > -
>>> > -#ifndef _LIBCPP_HAS_NO_STDOUT
>>> > -using ::printf;
>>> > -using ::putchar;
>>> > -using ::puts;
>>> > -using ::vprintf;
>>> > -#endif
>>> > -
>>> > -_LIBCPP_END_NAMESPACE_STD
>>> >
>>> > -#endif // _LIBCPP_CSTDIO
>>> > +#endif // _LIBCPP_STDIO_H
>>> >
>>> > Modified: libcxx/trunk/test/std/depr/depr.c.headers/stdio_h.pass.cpp
>>> > URL:
>>> http://llvm.org/viewvc/llvm-project/libcxx/trunk/test/std/depr/depr.c.headers/stdio_h.pass.cpp?rev=249798&r1=249797&r2=249798&view=diff
>>> >
>>> ==============================================================================
>>> > --- libcxx/trunk/test/std/depr/depr.c.headers/stdio_h.pass.cpp
>>> (original)
>>> > +++ libcxx/trunk/test/std/depr/depr.c.headers/stdio_h.pass.cpp Thu
>>> Oct 8 20:29:09 2015
>>> > @@ -13,6 +13,26 @@
>>> > #include <type_traits>
>>> > #include "test_macros.h"
>>> >
>>> > +#ifdef getc
>>> > +#error getc is defined
>>> > +#endif
>>> > +
>>> > +#ifdef putc
>>> > +#error putc is defined
>>> > +#endif
>>> > +
>>> > +#ifdef clearerr
>>> > +#error clearerr is defined
>>> > +#endif
>>> > +
>>> > +#ifdef feof
>>> > +#error feof is defined
>>> > +#endif
>>> > +
>>> > +#ifdef ferror
>>> > +#error ferror is defined
>>> > +#endif
>>> > +
>>> > #ifndef BUFSIZ
>>> > #error BUFSIZ not defined
>>> > #endif
>>> >
>>> >
>>> > _______________________________________________
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>>> > cfe-commits@lists.llvm.org
>>> > http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
>>>
>>> _______________________________________________
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>>
>>
>
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