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| author | Richard Smith <richard-llvm@metafoo.co.uk> | 2013-04-12 22:11:07 +0000 |
|---|---|---|
| committer | Richard Smith <richard-llvm@metafoo.co.uk> | 2013-04-12 22:11:07 +0000 |
| commit | 32b5013a7a443ff12cbaa5f3e2f86978179d5e04 (patch) | |
| tree | 2ae0dbd536fe05a0d7e2d679869fbc708ae6a79f /lib/Headers | |
| parent | 7332ae49671762239c9986c8f30f291c3a13d27e (diff) | |
tl;dr: Teach Clang to work around g++ changing its workaround to glibc's
implementation of C99's attempt to control the C++ standard. *sigh*
The C99 standard says that certain macros in <stdint.h>, such as SIZE_MAX,
should not be defined when the header is included in C++ mode, unless
__STDC_LIMIT_MACROS and __STDC_CONSTANT_MACROS are defined. The C++11 standard
says "Thanks, but no thanks" and C11 removed this rule, but various C library
implementations (such as glibc) follow C99 anyway.
g++ prior to 4.8 worked around the C99 / glibc behavior by defining
__STDC_*_MACROS in <cstdint>, which was incorrect, because <stdint.h> is
supposed to provide these macros too. g++ 4.8 works around it by defining
__STDC_*_MACROS in its builtin <stdint.h> header.
This change makes Clang act like g++ 4.8 in this regard: our <stdint.h> now
countermands any attempt by the C library to implement the undesired C99 rules,
by defining the __STDC_*_MACROS first. Unlike g++, we do this even in C++98
mode, since that was the intent of the C++ committee, matches the behavior
required in C11, and matches our built-in implementation of <stdint.h>.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179419 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Headers')
| -rw-r--r-- | lib/Headers/stdint.h | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/lib/Headers/stdint.h b/lib/Headers/stdint.h index 6f1a8761e1..051047f7d2 100644 --- a/lib/Headers/stdint.h +++ b/lib/Headers/stdint.h @@ -30,7 +30,48 @@ */ #if __STDC_HOSTED__ && \ defined(__has_include_next) && __has_include_next(<stdint.h>) + +// C99 7.18.3 Limits of other integer types +// +// Footnote 219, 220: C++ implementations should define these macros only when +// __STDC_LIMIT_MACROS is defined before <stdint.h> is included. +// +// Footnote 222: C++ implementations should define these macros only when +// __STDC_CONSTANT_MACROS is defined before <stdint.h> is included. +// +// C++11 [cstdint.syn]p2: +// +// The macros defined by <cstdint> are provided unconditionally. In particular, +// the symbols __STDC_LIMIT_MACROS and __STDC_CONSTANT_MACROS (mentioned in +// footnotes 219, 220, and 222 in the C standard) play no role in C++. +// +// C11 removed the problematic footnotes. +// +// Work around this inconsistency by always defining those macros in C++ mode, +// so that a C library implementation which follows the C99 standard can be +// used in C++. +# ifdef __cplusplus +# if !defined(__STDC_LIMIT_MACROS) +# define __STDC_LIMIT_MACROS +# define __STDC_LIMIT_MACROS_DEFINED_BY_CLANG +# endif +# if !defined(__STDC_CONSTANT_MACROS) +# define __STDC_CONSTANT_MACROS +# define __STDC_CONSTANT_MACROS_DEFINED_BY_CLANG +# endif +# endif + # include_next <stdint.h> + +# ifdef __STDC_LIMIT_MACROS_DEFINED_BY_CLANG +# undef __STDC_LIMIT_MACROS +# undef __STDC_LIMIT_MACROS_DEFINED_BY_CLANG +# endif +# ifdef __STDC_CONSTANT_MACROS_DEFINED_BY_CLANG +# undef __STDC_CONSTANT_MACROS +# undef __STDC_CONSTANT_MACROS_DEFINED_BY_CLANG +# endif + #else /* C99 7.18.1.1 Exact-width integer types. |