configure.ac: use C++ compiler for linking, replaces -lstdc++

If at least one source is C++, ask the C++ compiler to link the
executable instead of manually adding `-lstdc++`.  The C++ compiler
knows best which C++ standard library needs to be used.  This is more
robust, and allows non-GNU standard libraries such as libc++.

Author: MaxKellermann

build/php.m4

@@ -742,7 +742,6 @@ AC_DEFUN([PHP_REQUIRE_CXX],[
   if test -z "$php_cxx_done"; then
     AC_PROG_CXX
     AC_PROG_CXXCPP
-    PHP_ADD_LIBRARY(stdc++)
     php_cxx_done=yes
   fi
 ])

configure.ac

@@ -1664,15 +1664,24 @@ CFLAGS_CLEAN="$CFLAGS \$(PROF_FLAGS)"
 CFLAGS="\$(CFLAGS_CLEAN) $standard_libtool_flag"
 CXXFLAGS="$CXXFLAGS $standard_libtool_flag \$(PROF_FLAGS)"
 
+if test -z "$php_cxx_done"; then
+  # Link with the C compiler
+  LINK_SAPI="\$(CC) -export-dynamic \$(CFLAGS_CLEAN) \$(EXTRA_CFLAGS)"
+else
+  # We have at least one C++ source: we have to link with the C++
+  # compiler so the correct C++ standard library gets linked
+  LINK_SAPI="\$(CXX) -export-dynamic \$(CXXFLAGS_CLEAN) \$(EXTRA_CXXFLAGS)"
+fi
+
 case $host_alias in
 *aix*)
-  LINK_SAPI="\$(LIBTOOL) --mode=link \$(CC) -export-dynamic \$(CFLAGS_CLEAN) \$(EXTRA_CFLAGS) \$(EXTRA_LDFLAGS_PROGRAM) \$(LDFLAGS) -Wl,-brtl \$(PHP_RPATHS)"
+  LINK_SAPI="\$(LIBTOOL) --mode=link $LINK_SAPI -export-dynamic \$(EXTRA_LDFLAGS_PROGRAM) \$(LDFLAGS) -Wl,-brtl \$(PHP_RPATHS)"
   ;;
 *darwin*)
-  LINK_SAPI="\$(CC) \$(CFLAGS_CLEAN) \$(EXTRA_CFLAGS) \$(EXTRA_LDFLAGS_PROGRAM) \$(LDFLAGS) \$(NATIVE_RPATHS) \$(PHP_FRAMEWORKS)"
+  LINK_SAPI="$LINK_SAPI \$(EXTRA_LDFLAGS_PROGRAM) \$(LDFLAGS) \$(NATIVE_RPATHS) \$(PHP_FRAMEWORKS)"
   ;;
 *)
-  LINK_SAPI="\$(LIBTOOL) --mode=link \$(CC) -export-dynamic \$(CFLAGS_CLEAN) \$(EXTRA_CFLAGS) \$(EXTRA_LDFLAGS_PROGRAM) \$(LDFLAGS) \$(PHP_RPATHS)"
+  LINK_SAPI="\$(LIBTOOL) --mode=link $LINK_SAPI -export-dynamic \$(EXTRA_LDFLAGS_PROGRAM) \$(LDFLAGS) \$(PHP_RPATHS)"
   ;;
 esac