Whether the following names are declared by glibc depends on __USE_ISOC99, but not __USE_ISOCXX11. They are only declared for C++ programs because g++ unconditionally pre-defines _GNU_SOURCE for all compilations on GNU targets. I want G++ to move away from predefining _GNU_SOURCE, because causes many problems, e.g. non-standard names such as M_PI are always declared in C++ programs. Before we could do that, glibc would need to ensure all C99 functions that are also part of C++11 would be declared for C++ code, without relying on _GNU_SOURCE. That could be done by either making many changes like this: --- a/ctype/ctype.h +++ b/ctype/ctype.h @@ -126,7 +126,7 @@ extern int toupper (int __c) __THROW; /* ISO C99 introduced one new function. */ -#ifdef __USE_ISOC99 +#if defined __USE_ISOC99 || __USE_ISOCXX11 __exctype (isblank); #endif Or simply: --- a/include/features.h +++ b/include/features.h @@ -243,6 +243,7 @@ #if ((defined __cplusplus && __cplusplus >= 201103L) \ || defined __GXX_EXPERIMENTAL_CXX0X__) # define __USE_ISOCXX11 1 +# define __USE_ISOC99 1 #endif /* If none of the ANSI/POSIX macros are defined, or if _DEFAULT_SOURCE The former approach is already used in a very small number of places: stdlib/stdlib.h:462:#if defined __USE_ISOC11 || defined __USE_ISOCXX11 stdlib/stdlib.h:484:#if defined __USE_ISOC11 || defined __USE_ISOCXX11 wcsmbs/uchar.h:40:#if defined __GNUC__ && !defined __USE_ISOCXX11 I can provide patches if you tell me which direction would be preferred. The ISO C and ISO C++ names that are not declared by glibc when G++ doesn't predefine _GNU_SOURCE are: FP_INFINITE FP_NAN FP_NORMAL FP_SUBNORMAL FP_ZERO isblank double_t float_t acosh acoshf acoshl asinh asinhf asinhl atanh atanhf atanhl cbrt cbrtf cbrtl copysign copysignf copysignl erf erff erfl erfc erfcf erfcl exp2 exp2f exp2l expm1 expm1f expm1l fdim fdimf fdiml fma fmaf fmal fmax fmaxf fmaxl fmin fminf fminl hypot hypotf hypotl ilogb ilogbf ilogbl lgamma lgammaf lgammal llrint llrintf llrintl llround llroundf llroundl log1p log1pf log1pl log2 log2f log2l logb logbf logbl lrint lrintf lrintl lround lroundf lroundl nan nanf nanl nearbyint nearbyintf nearbyintl nextafter nextafterf nextafterl nexttoward nexttowardf nexttowardl remainder remainderf remainderl remquo remquof remquol rint rintf rintl round roundf roundl scalbln scalblnf scalblnl scalbn scalbnf scalbnl tgamma tgammaf tgammal trunc truncf truncl snprintf vfscanf vscanf vsnprintf vsscanf lldiv_t llabs lldiv atoll strtoll strtoull strtof strtold fwide fwprintf fwscanf swprintf swscanf vfwprintf vfwscanf vswprintf vswscanf vwprintf vwscanf wcstof wprintf wscanf wcstold wcstoll wcstoull iswblank
On a related topic, there is this comment in features.h /* This is to enable compatibility for ISO C++11. So far g++ does not provide a macro. Check the temporary macro for now, too. */ #if ((defined __cplusplus && __cplusplus >= 201103L) \ || defined __GXX_EXPERIMENTAL_CXX0X__) # define __USE_ISOCXX11 1 #endif Should it define some other macro? Isn't __cplusplus the right thing to check?
(In reply to Jonathan Wakely from comment #1) > On a related topic, there is this comment in features.h > > /* This is to enable compatibility for ISO C++11. > > So far g++ does not provide a macro. Check the temporary macro for > now, too. */ > #if ((defined __cplusplus && __cplusplus >= 201103L) > \ > || defined __GXX_EXPERIMENTAL_CXX0X__) > # define __USE_ISOCXX11 1 > #endif > > Should it define some other macro? Isn't __cplusplus the right thing to > check? If you're expecting something like __STDC_VERSION__ for C++, that's exactly what __cplusplus is, so I don't know what "So far g++ does not provide a macro" means. However, that reminds me of another alternative solution to the main problem, G++ could predefine __STDC_VERSION__ to 19901L for C++11 and C++14, and to 201112L for C++17. That would cause glibc to declare the C library functions that C++ wants. The C++ standard says: "Whether __STDC_VERSION__ is predefined and if so, what its value is, are implementation-defined." So it would be OK for G++ to do that, as a way of requesting libc to declare the corresponding features.
I think __USE_ISOC99 and __USE_ISOC11 should be defined for whatever C++ versions incorporate the relevant C library versions.
--- a/include/features.h +++ b/include/features.h @@ -236,13 +236,18 @@ # define __USE_ISOC95 1 #endif +#ifdef __cplusplus +/* This is to enable compatibility for ISO C++17. */ +#if (__cplusplus >= 201703L) +# define __USE_ISOCXX17 1 +# define __USE_ISOC11 1 +#endif /* This is to enable compatibility for ISO C++11. - - So far g++ does not provide a macro. Check the temporary macro for - now, too. */ -#if ((defined __cplusplus && __cplusplus >= 201103L) \ - || defined __GXX_EXPERIMENTAL_CXX0X__) + Check the temporary macro for now, too. */ +#if (__cplusplus >= 201103L || defined __GXX_EXPERIMENTAL_CXX0X__) # define __USE_ISOCXX11 1 +# define __USE_ISOC99 1 +#endif #endif /* If none of the ANSI/POSIX macros are defined, or if _DEFAULT_SOURCE
This is an automated email from the git hooks/post-receive script. It was generated because a ref change was pushed to the repository containing the project "GNU C Library master sources". The branch, master has been updated via d6c064e914cba3277d852c9fa27db53f0059ff8c (commit) from 645ac9aaf89e3311949828546df6334322f48933 (commit) Those revisions listed above that are new to this repository have not appeared on any other notification email; so we list those revisions in full, below. - Log ----------------------------------------------------------------- https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=d6c064e914cba3277d852c9fa27db53f0059ff8c commit d6c064e914cba3277d852c9fa27db53f0059ff8c Author: Jonathan Wakely <jwakely@redhat.com> Date: Mon Oct 9 14:58:34 2017 +0100 Ensure C99 and C11 interfaces are available for C++ [BZ #21326] This patch ensures that the C99 and C11 features required by C++ are defined according to the value of the __cplusplus macro, and not just because G++ always defines _GNU_SOURCE. This will allow G++ to stop defining _GNU_SOURCE some day, without causing the C99 and C11 interfaces to disappear for C++ programs. [BZ #21326] * include/features.h [__cplusplus >= 201103] (__USE_ISOC99): Define. [__cplusplus >= 201703] (__USE_ISOCXX17, __USE_ISOC11): Define. * math/Makefile (test-math-cxx11): New test. * math/test-math-cxx11.cc: New file. ----------------------------------------------------------------------- Summary of changes: ChangeLog | 8 +++ include/features.h | 17 +++-- math/Makefile | 4 +- math/test-math-cxx11.cc | 160 +++++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 182 insertions(+), 7 deletions(-) create mode 100644 math/test-math-cxx11.cc
Fixed in 2.27.