Re: GDB 7.99.91 MinGW compilation error in cli-script.c

[Eli Zaretskii <eliz@gnu.org>]

The error manifests itself as follows:

       g++ -std=gnu++11 -O2 -gdwarf-4 -g3    -I. -I. -I./common -I./config  -DLOCALEDIR="\"d:/usr/share/locale\"" -DHAVE_CONFIG_H -I./../include/opcode -I./../opcodes/.. -I./../readline/..   -I../bfd -I./../bfd -I./../include -I../libdecnumber -I./../libdecnumber   -I./gnulib/import -Ibuild-gnulib/import   -DTUI=1   -Id:/usr/include -Id:/usr/include/guile/2.0 -Id:/usr/include   -Id:/usr/Python26/include -Id:/usr/Python26/include -Wall -Wpointer-arith -Wno-unused -Wunused-value -Wunused-function -Wno-switch -Wno-char-subscripts -Wempty-body -Wunused-but-set-parameter -Wunused-but-set-variable -Wno-sign-compare -Wno-narrowing -Wno-format  -c -o cli-script.o -MT cli-script.o -MMD -MP  -MF .deps/cli-script.Tpo cli/cli-script.c
       cli/cli-script.c: In member function 'std::__cxx11::string user_args::insert_args(const char*) const':
       cli/cli-script.c:809:16: error: 'to_string' is not a member of 'std'
	   new_line += std::to_string (m_args.size ());
		       ^
       Makefile:1888: recipe for target `cli-script.o' failed
       make[2]: *** [cli-script.o] Error 1

The reason is that std::to_string is guarded by the symbol
_GLIBCXX_HAVE_BROKEN_VSWPRINTF, which mingw.org's MinGW defines in its
os_defines.h, because msvcrt.dll's implementation of vswprintf is
incompatible with what C++11 expects.  So GDB assumes here without
testing that this method is available, which is not true at least on
one platform.

How best to solve this?  I worked around by providing my own
implementation based on std::ostringstream, but I'm not sure this is
TRT.  An alternative would be to use some less problematic API, since
currently cli-script.c is the only user of this method, and its needs
are quite modest.  And if we do provide a replacement for to_string,
should the configure script probe for it, or should we condition it
specifically on MinGW and _GLIBCXX_HAVE_BROKEN_VSWPRINTF?

Thoughts?