Patch #1324762: Change --with-cxx to --with-cxx-main.

Makefile.pre.in

@@ -30,6 +30,7 @@ VPATH=		@srcdir@
 
 CC=		@CC@
 CXX=		@CXX@
+MAINCC=		@MAINCC@
 LINKCC=		@LINKCC@
 AR=		@AR@
 RANLIB=		@RANLIB@
@@ -157,7 +158,6 @@ LIBC=		@LIBC@
 SYSLIBS=	$(LIBM) $(LIBC)
 SHLIBS=		@SHLIBS@
 
-MAINOBJ=	@MAINOBJ@
 THREADOBJ=	@THREADOBJ@
 DLINCLDIR=	@DLINCLDIR@
 DYNLOADFILE=	@DYNLOADFILE@
@@ -326,9 +326,9 @@ LIBRARY_OBJS=	\
 all:		$(BUILDPYTHON) oldsharedmods sharedmods
 
 # Build the interpreter
-$(BUILDPYTHON):	Modules/$(MAINOBJ) $(LIBRARY) $(LDLIBRARY)
+$(BUILDPYTHON):	Modules/python.o $(LIBRARY) $(LDLIBRARY)
 		$(LINKCC) $(LDFLAGS) $(LINKFORSHARED) -o $@ \
-			Modules/$(MAINOBJ) \
+			Modules/python.o \
 			$(BLDLIBRARY) $(LIBS) $(MODLIBS) $(SYSLIBS) $(LDLAST)
 
 platform: $(BUILDPYTHON)
@@ -448,8 +448,8 @@ Modules/getpath.o: $(srcdir)/Modules/getpath.c Makefile
 		-DVPATH='"$(VPATH)"' \
 		-o $@ $(srcdir)/Modules/getpath.c
 
-Modules/ccpython.o: $(srcdir)/Modules/ccpython.cc
-	$(CXX) -c $(PY_CFLAGS) -o $@ $(srcdir)/Modules/ccpython.cc
+Modules/python.o: $(srcdir)/Modules/python.c
+	$(MAINCC) -c $(PY_CFLAGS) -o $@ $(srcdir)/Modules/python.c
 
 
 $(GRAMMAR_H) $(GRAMMAR_C): $(PGEN) $(GRAMMAR_INPUT)
@@ -537,7 +537,7 @@ PYTHON_HEADERS= \
 		Include/weakrefobject.h \
 		pyconfig.h
 
-$(LIBRARY_OBJS) $(MODOBJS) Modules/$(MAINOBJ): $(PYTHON_HEADERS)
+$(LIBRARY_OBJS) $(MODOBJS) Modules/python.o: $(PYTHON_HEADERS)
 
 
 ######################################################################
@@ -813,7 +813,7 @@ libainstall:	all
 		fi; \
 	fi
 	$(INSTALL_DATA) Modules/config.c $(DESTDIR)$(LIBPL)/config.c
-	$(INSTALL_DATA) Modules/$(MAINOBJ) $(DESTDIR)$(LIBPL)/$(MAINOBJ)
+	$(INSTALL_DATA) Modules/python.o $(DESTDIR)$(LIBPL)/python.o
 	$(INSTALL_DATA) $(srcdir)/Modules/config.c.in $(DESTDIR)$(LIBPL)/config.c.in
 	$(INSTALL_DATA) Makefile $(DESTDIR)$(LIBPL)/Makefile
 	$(INSTALL_DATA) Modules/Setup $(DESTDIR)$(LIBPL)/Setup

Misc/NEWS

@@ -82,6 +82,11 @@ Library
 Build
 -----
 
+- Patch #1324762:Remove ccpython.cc; replace --with-cxx with
+  --with-cxx-main. Link with C++ compiler only if --with-cxx-main was
+  specified. (Can be overriden by explicitly setting LINKCC.) Decouple
+  CXX from --with-cxx-main, see description in README.
+
 - Patch #1429775: Link extension modules with the shared libpython.
 
 C API

Modules/ccpython.cc

-/* Minimal main program -- everything is loaded from the library */
-
-#include "Python.h"
-
-extern "C"
-DL_EXPORT(int) Py_Main( int argc, char *argv[] );
-
-int main( int argc, char *argv[] )
-{
-	return Py_Main(argc, argv);
-}

README

@@ -1045,13 +1045,35 @@ Modules/getpath.o.
 --with-libs='libs': Add 'libs' to the LIBS that the python interpreter
         is linked against.
 
---with-cxx=<compiler>: Some C++ compilers require that main() is
-        compiled with the C++ if there is any C++ code in the application.
-        Specifically, g++ on a.out systems may require that to support
-        construction of global objects. With this option, the main() function
-        of Python will be compiled with <compiler>; use that only if you
-        plan to use C++ extension modules, and if your compiler requires
-        compilation of main() as a C++ program.
+--with-cxx-main=<compiler>: If you plan to use C++ extension modules,
+        then -- on some platforms -- you need to compile python's main()
+        function with the C++ compiler. With this option, make will use
+        <compiler> to compile main() *and* to link the python executable.
+        It is likely that the resulting executable depends on the C++
+        runtime library of <compiler>. (The default is --without-cxx-main.)
+
+        There are platforms that do not require you to build Python
+        with a C++ compiler in order to use C++ extension modules.
+        E.g., x86 Linux with ELF shared binaries and GCC 3.x, 4.x is such
+        a platform. We recommend that you configure Python
+        --without-cxx-main on those platforms because a mismatch
+        between the C++ compiler version used to build Python and to
+        build a C++ extension module is likely to cause a crash at
+        runtime.
+
+        The Python installation also stores the variable CXX that
+        determines, e.g., the C++ compiler distutils calls by default
+        to build C++ extensions. If you set CXX on the configure command
+        line to any string of non-zero length, then configure won't
+        change CXX. If you do not preset CXX but pass
+        --with-cxx-main=<compiler>, then configure sets CXX=<compiler>.
+        In all other cases, configure looks for a C++ compiler by
+        some common names (c++, g++, gcc, CC, cxx, cc++, cl) and sets
+        CXX to the first compiler it finds. If it does not find any
+        C++ compiler, then it sets CXX="".
+
+        Similarly, if you want to change the command used to link the
+        python executable, then set LINKCC on the configure command line.
 
 
 --with-pydebug:  Enable additional debugging code to help track down

configure.in

@@ -313,64 +313,69 @@ AC_ARG_WITH(gcc,
 	esac])
 AC_MSG_RESULT($without_gcc)
 
+# If the user switches compilers, we can't believe the cache
+if test ! -z "$ac_cv_prog_CC" -a ! -z "$CC" -a "$CC" != "$ac_cv_prog_CC"
+then
+  AC_MSG_ERROR([cached CC is different -- throw away $cache_file
+(it is also a good idea to do 'make clean' before compiling)])
+fi
+
+AC_PROG_CC
+
 AC_SUBST(CXX)
-AC_SUBST(MAINOBJ)
-MAINOBJ=python.o
-AC_MSG_CHECKING(for --with-cxx=<compiler>)
-AC_ARG_WITH(cxx,
-            AC_HELP_STRING(--with-cxx=<compiler>, enable C++ support),
+AC_SUBST(MAINCC)
+AC_MSG_CHECKING(for --with-cxx-main=<compiler>)
+AC_ARG_WITH(cxx_main,
+            AC_HELP_STRING([--with-cxx-main=<compiler>],
+                           [compile main() and link python executable with C++ compiler]),
 [
-	check_cxx=no
+	
 	case $withval in
-	no)	CXX=
-		with_cxx=no;;
-	*)	CXX=$withval
-		MAINOBJ=ccpython.o
-		with_cxx=$withval;;
+	no)	with_cxx_main=no
+		MAINCC='$(CC)';;
+	yes)	with_cxx_main=yes
+		MAINCC='$(CXX)';;
+	*)	with_cxx_main=yes
+		MAINCC=$withval
+		if test -z "$CXX"
+		then
+			CXX=$withval
+		fi;;
 	esac], [
-	with_cxx=no
-	check_cxx=yes
+	with_cxx_main=no
+	MAINCC='$(CC)'
 ])
-AC_MSG_RESULT($with_cxx)
+AC_MSG_RESULT($with_cxx_main)
 
-if test "$with_cxx" = "yes"
+preset_cxx="$CXX"
+if test -z "$CXX"
 then
-	AC_MSG_ERROR([must supply a compiler when using --with-cxx])
+        case "$CC" in
+        gcc)    AC_PATH_PROG(CXX, [g++], [g++], [notfound]) ;;
+        cc)     AC_PATH_PROG(CXX, [c++], [c++], [notfound]) ;;
+        esac
+	if test "$CXX" = "notfound"
+	then
+		CXX=""
+	fi
 fi
-
-dnl The following fragment works similar to AC_PROG_CXX.
-dnl It does not fail if CXX is not found, and it is not executed if 
-dnl --without-cxx was given.
-dnl Finally, it does not test whether CXX is g++.
-
-dnl Autoconf 2.5x does not have AC_PROG_CXX_WORKS anymore
-ifdef([AC_PROG_CXX_WORKS],[],
-      [AC_DEFUN([AC_PROG_CXX_WORKS],
-      [AC_LANG_PUSH(C++)dnl
-       _AC_COMPILER_EXEEXT
-       AC_LANG_POP()
-      ]
-)])
-
-if test "$check_cxx" = "yes" 
+if test -z "$CXX"
 then
 	AC_CHECK_PROGS(CXX, $CCC c++ g++ gcc CC cxx cc++ cl, notfound)
 	if test "$CXX" = "notfound"
 	then
-		CXX=
-	else
-		AC_PROG_CXX_WORKS
+		CXX=""
 	fi
 fi
-
-# If the user switches compilers, we can't believe the cache
-if test ! -z "$ac_cv_prog_CC" -a ! -z "$CC" -a "$CC" != "$ac_cv_prog_CC"
+if test "$preset_cxx" != "$CXX"
 then
-  AC_MSG_ERROR([cached CC is different -- throw away $cache_file
-(it is also a good idea to do 'make clean' before compiling)])
+        AC_MSG_WARN([
+
+  By default, distutils will build C++ extension modules with "$CXX".
+  If this is not intended, then set CXX on the configure command line.
+  ])
 fi
 
-AC_PROG_CC
 
 # checks for UNIX variants that set C preprocessor variables
 AC_AIX
@@ -480,22 +485,7 @@ AC_SUBST(LINKCC)
 AC_MSG_CHECKING(LINKCC)
 if test -z "$LINKCC"
 then
-        if test -z "$CXX"; then
-              LINKCC="\$(PURIFY) \$(CC)"
-        else
-              echo 'extern "C" void foo();int main(){foo();}' > conftest_a.cc
-              $CXX -c conftest_a.cc # 2>&5
-              echo 'void foo(){}' > conftest_b.$ac_ext
-              $CC -c conftest_b.$ac_ext # 2>&5
-              if $CC -o conftest$ac_exeext conftest_a.$ac_objext conftest_b.$ac_objext 2>&5 \
-                 && test -s conftest$ac_exeext && ./conftest$ac_exeext
-              then
-                 LINKCC="\$(PURIFY) \$(CC)"
-              else
-                 LINKCC="\$(PURIFY) \$(CXX)"
-              fi
-              rm -fr conftest*
-        fi
+	LINKCC='$(PURIFY) $(MAINCC)'
 	case $ac_sys_system in
 	AIX*)
 	   exp_extra="\"\""