Re: autoconf vs <cstdint>

[Ralf Corsepius]

On 12/02/2009 04:44 AM, Erik de Castro Lopo wrote:
> Eric Blake wrote:
>
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA1
> >
> > According to Erik de Castro Lopo on 12/1/2009 8:12 PM:
> > >      AC_LANG([C++])
> > >      AC_ADD_CXXFLAGS([-std=gnu++0x])
> > >      AC_CHECK_HEADER(cstdint)
> >
> > With proper m4 quoting, that would be:
> >
> > AC_CHECK_HEADER([cstdint])
> >
> > >      checking cstdint usability... yes
> > >      checking cstdint presence... no
> > >      configure: WARNING: cstdint: accepted by the compiler, rejected by the 
> > > preprocessor!
> > >      configure: WARNING: cstdint: proceeding with the compiler's result
> > >      checking for cstdint... yes
> >
> > Can we see the corresponding config.log?
>
> Ah, that shed some light:
>
>      configure:18130: checking if g++ accepts -std=gnu++0x
>      configure:18147: g++ -o conftest -g -O2 -Wall -Wextra -Wsign-compare 
> -Wno-ctor-dtor-privacy
>          -Wno-non-virtual-dtor -Wformat -Werror -Wno-deprecated -std=gnu++0x   
> conftest.cpp -lcups>&5
>      configure:18147: $? = 0
>      configure:18148: result: yes
>      configure:18160: checking cstdint usability
>      configure:18160: g++ -c -g -O2 -Wall -Wextra -Wsign-compare 
> -Wno-ctor-dtor-privacy \
>          -Wno-non-virtual-dtor -Wformat -Werror -Wno-deprecated -std=gnu++0x  
> conftest.cpp>&5
>      configure:18160: $? = 0
>      configure:18160: result: yes
>      configure:18160: checking cstdint presence
>      configure:18160: g++ -E  conftest.cpp
>      In file included from /usr/include/c++/4.4/cstdint:35,
>                   from conftest.cpp:32:
>      /usr/include/c++/4.4/c++0x_warning.h:31:2: error: #error This file 
> requires compiler and
>           library support for the upcoming ISO C++ standard, C++0x. This 
> support is currently
>           experimental, and must be enabled with the -std=c++0x or -std=gnu++0x 
> compiler options.
>      configure:18160: $? = 1
>
>
> The problem is that when checking for<cstdint>, -std=gnu++0x is not on the
> command line.

Look again. AFAIS from your config.log, -std=gnu++0x is on the command line.

AFAICT, your problem is you using -Werror. By applying it the warning 
gcc issues becomes an error which causes the check in configure to break.

Ralf