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Re: signbit issues

From: Orion Poplawski
Subject: Re: signbit issues
Date: Fri, 19 Feb 2016 15:43:08 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0

On 02/19/2016 12:45 PM, Paul Eggert wrote:
> On 02/19/2016 11:32 AM, Orion Poplawski wrote:
>> g++ -DHAVE_CONFIG_H -I. -I..  -I../lib   -g -O2 -MT foobar.o -MD -MP -MF
>> .deps/foobar.Tpo -c -o foobar.o foobar.cpp
>> In file included from foobar.cpp:3:0:
>> ../lib/math.h: In function ‘int signbit(float)’:
>> ../lib/math.h:2576:1: error: ‘int signbit(float)’ conflicts with a previous
>> declaration
> This is a C++ thing, plus I don't have GCC 6, so I'm afraid you'll have to do
> most of the legwork.
> Why was Gnulib trying to define its own signbit function? Why didn't the
> signbit function from GCC 6 pass Gnulib's test? Look in config.log to find
> out. On my platform (Fedora 23, GCC 5.3.1) signbit passes all the tests so
> there's no reason for Gnulib to try to substitute its own.

Another thing that may be relevant - it appears that with 6.0.0,
/usr/include/c++/6.0.0/cmath does:

#include_next <math.h>

which appears to have the effect of forcing it to include /usr/include/math.h
instead of the math.h from gnulib, which I expect is how gnulib worked before.

Orion Poplawski
Technical Manager                     303-415-9701 x222
NWRA, Boulder/CoRA Office             FAX: 303-415-9702
3380 Mitchell Lane                       address@hidden
Boulder, CO 80301                   http://www.nwra.com

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