g++ cannot find std::stoi

[Dimitry Andric]

On 02 Jun 2014, at 15:49, hhh at sdf.org wrote:
> Lowell Gilbert <freebsd-ports-local at be-well.ilk.org> writes:
> 
>> hhh at sdf.org writes:
>> 
>>> I'm trying to compile OpenCog [1] using g++47, but get an error about
>>> missing std::stoi.
>>> 
>>> I have attached a micro-example [2] that generates the same error, if I
>>> try to compile it with:
>>> 
>>> % g++47 -std=c++11 s.cc
>>> s.cc: In function 'int main()':
>>> s.cc:8:13: error: 'stoi' is not a member of 'std'
>>> 
>>> 
>>> There are no problems neither with clang nor with g++ on Debian:
>>> 
>>> % clang++ -std=c++11 s.cc
>>> 
>>> 
>>> 
>>> What am I missing?
>> 
>> An old libc++ bug in gcc.
>> 
>> You need a newer compiler.
> 
> I tried with gcc49 and it seem to have the same problem.

This is because gcc's basic_string.h (from gcc 4.8 and higher) has the
following conditional for declaring std::stoi() and friends:

#if ((__cplusplus >= 201103L) && defined(_GLIBCXX_USE_C99) \
     && !defined(_GLIBCXX_HAVE_BROKEN_VSWPRINTF))

Unfortunately libstdc++'s configure script thinks FreeBSD does not have
proper C99 support, so it undefines _GLIBCXX_USE_C99, see
/usr/local/lib/gcc48/include/c++/i386-portbld-freebsd11.0/bits/c++config.h
around line 1238:

/* Define if C99 functions or macros from <wchar.h>, <math.h>, <complex.h>,
   <stdio.h>, and <stdlib.h> can be used or exposed. */
/* #undef _GLIBCXX_USE_C99 */

This is also the case for the copy of c++config.h in the base system.
The libstdc++ configure script says the following (excerpted):

...
configure:16721: checking for ISO C99 support in <complex.h>
configure:16852: g++48 -o conftest  -std=c++98 -fno-exceptions   conftest.cpp  -lm >&5
conftest.cpp: In function 'int main()':
conftest.cpp:52:19: error: 'clogf' was not declared in this scope
  tmpf = clogf(tmpf);
                   ^
conftest.cpp:58:25: error: 'cpowf' was not declared in this scope
  tmpf = cpowf(tmpf, tmpf);
                         ^
conftest.cpp:65:18: error: 'clog' was not declared in this scope
  tmpd = clog(tmpd);
                  ^
conftest.cpp:71:24: error: 'cpow' was not declared in this scope
  tmpd = cpow(tmpd, tmpd);
                        ^
conftest.cpp:75:21: error: 'ccosl' was not declared in this scope
  tmpld = ccosl(tmpld);
                     ^
conftest.cpp:76:22: error: 'ccoshl' was not declared in this scope
  tmpld = ccoshl(tmpld);
                      ^
conftest.cpp:77:21: error: 'cexpl' was not declared in this scope
  tmpld = cexpl(tmpld);
                     ^
conftest.cpp:78:21: error: 'clogl' was not declared in this scope
  tmpld = clogl(tmpld);
                     ^
conftest.cpp:79:21: error: 'csinl' was not declared in this scope
  tmpld = csinl(tmpld);
                     ^
conftest.cpp:80:22: error: 'csinhl' was not declared in this scope
  tmpld = csinhl(tmpld);
                      ^
conftest.cpp:82:21: error: 'ctanl' was not declared in this scope
  tmpld = ctanl(tmpld);
                     ^
conftest.cpp:83:22: error: 'ctanhl' was not declared in this scope
  tmpld = ctanhl(tmpld);
                      ^
conftest.cpp:84:28: error: 'cpowl' was not declared in this scope
  tmpld = cpowl(tmpld, tmpld);
                            ^
...
configure:16861: result: no
configure:16870: checking for ISO C99 support in <stdio.h>
configure:16927: g++48 -o conftest  -std=c++98 -fno-exceptions   conftest.cpp  -lm >&5
conftest.cpp: In function 'int main()':
conftest.cpp:47:23: warning: deprecated conversion from string constant to 'char*' [-Wwrite-strings]
 snprintf("12", 0, "%i");
                       ^
configure:16927: $? = 0
configure:16938: result: yes
configure:16942: checking for ISO C99 support in <stdlib.h>
configure:17011: g++48 -o conftest  -std=c++98 -fno-exceptions   conftest.cpp  -lm >&5
conftest.cpp:38:7: error: 'lldiv_t' does not name a type
       lldiv_t mydivt;
       ^
conftest.cpp: In function 'int main()':
conftest.cpp:45:35: error: 'strtoll' was not declared in this scope
       ll = strtoll("gnu", &tmp, 10);
                                   ^
conftest.cpp:46:36: error: 'strtoull' was not declared in this scope
       ll = strtoull("gnu", &tmp, 10);
                                    ^
conftest.cpp:47:20: error: 'llabs' was not declared in this scope
       ll = llabs(10);
                    ^
conftest.cpp:48:7: error: 'mydivt' was not declared in this scope
       mydivt = lldiv(10,1);
       ^
conftest.cpp:48:26: error: 'lldiv' was not declared in this scope
       mydivt = lldiv(10,1);
                          ^
conftest.cpp:51:22: error: 'atoll' was not declared in this scope
       ll = atoll("10");
                      ^
...
configure:17022: result: no
configure:17029: checking for ISO C99 support in <wchar.h>
configure:17049: g++48 -c  -std=c++98 -fno-exceptions  conftest.cpp >&5
conftest.cpp:38:17: error: '::wcstoll' has not been declared
         using ::wcstoll;
                 ^
conftest.cpp:39:17: error: '::wcstoull' has not been declared
         using ::wcstoull;
                 ^
...
configure:17182: checking for fully enabled ISO C99 support
configure:17184: result: no

The end result is that quite a lot of functionality in libstdc++'s
headers is being disabled because of this.

My advice is to use libc++ for now, which has no such problems, and can
also be used with gcc 4.8 or higher.

-Dimitry

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