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isnan function conflicts with C++ standard library declarations
From: |
Martin Storsjö |
Subject: |
isnan function conflicts with C++ standard library declarations |
Date: |
Tue, 27 Aug 2019 23:21:30 +0300 (EEST) |
User-agent: |
Alpine 2.20 (DEB 67 2015-01-07) |
Hi,
When the isnan function is enabled in gnulib, the added bits in math.h
break if included in C++ translation units.
A minimal reproducion example is available at
https://martin.st/temp/gnulib-isnan-repro-0.0.0.tar.gz (preconfigured and
directly buildable) and
https://martin.st/temp/gnulib-isnan-repro-source.tar.gz (original source,
requires running gnulib-tool and autoreconf).
The error manifests both with GCC/libstdc++ and Clang/libc++, with error
messages like these:
In file included from myprog.cpp:2:0:
lib/math.h: In function ‘int isnan(float)’:
lib/math.h:2829:1: error: ‘int isnan(float)’ conflicts with a previous
declaration
_GL_MATH_CXX_REAL_FLOATING_DECL_2 (isnan)
^
In file included from /usr/include/c++/7/math.h:36:0,
from lib/math.h:27,
from myprog.cpp:2:
/usr/include/c++/7/cmath:618:3: note: previous declaration ‘constexpr bool
std::isnan(float)’
isnan(float __x)
^~~~~
Or this:
In file included from myprog.cpp:2:
lib/math.h:2829:36: error: 'isnan' is missing exception specification 'throw()'
_GL_MATH_CXX_REAL_FLOATING_DECL_2 (isnan)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/math.h:533:1:
note:
previous declaration is here
isnan(float __lcpp_x) _NOEXCEPT { return __libcpp_isnan(__lcpp_x); }
^
This issue can crop up e.g. when trying to build gettext for mingw (which
has got the gnulib isnan function bundled, even if it isn't used).
// Martin
- isnan function conflicts with C++ standard library declarations,
Martin Storsjö <=