correct configure error without g++ #5177

SLES12, gcc added (no g++), current master

./configure prints:

... checking for g++... no checking for objc++... no checking for objcxx... no checking for c++... no checking for CXX... no checking whether we are using the GNU Objective C++ compiler... no checking whether g++ accepts -g... no checking dependency style of g++... none checking for a sed that does not truncate output... (cached) /usr/bin/sed checking for ar... /usr/bin/ar checking for ranlib... /usr/bin/ranlib checking for strip... /usr/bin/strip checking for gcov... /usr/bin/gcov checking for lcov... no checking for java... no checking for genhtml... no checking for git... /usr/bin/git checking for ccache... no checking for xgettext... no checking for hexdump... /usr/bin/hexdump checking for pkg-config... /usr/bin/pkg-config checking pkg-config is at least version 0.9.0... yes checking whether byte ordering is bigendian... yes configure: error: "Big Endian not supported"

config.log contains:

./configure: line 2111: g++: command not found

It should report g++ is needed instead of "Big Endian not supported."

This is because AC_PROG_CXX doesn't check whether the compiler actually works. See

http://lists.gnu.org/archive/html/bug-autoconf/2010-05/msg00002.html

for more details.

Something like this should fix it:

... dnl Checks for programs.

dnl Macro for checking C++ compiler dnl ... AC_PROG_CXX is not checking if the compiler works! AC_DEFUN([AC_PROG_CXX_WORKS], [AC_REQUIRE([AC_PROG_CXX])dnl AC_CACHE_CHECK([whether the C++ compiler works], [_cv_cxx_works], [AC_LANG_PUSH([C++]) AC_LINK_IFELSE([AC_LANG_PROGRAM([], [])], [_cv_cxx_works=yes], [_cv_cxx_works=no]) AC_LANG_POP([C++])]) ])

AC_PROG_CXX AC_PROG_CXX_WORKS

if test "x$_cv_cxx_works" = xno; then AC_MSG_ERROR("C++ compiler doesn't work.") fi

AC_PROG_CC ...

Fixed by #5214