Issue #9189: Allow users to set $CFLAGS, $CPPFLAGS, and $LDFLAGS when running

configure to append to Python's default values for those variables, and
similarly allow users to set $XXFLAGS on the make command line to append to the
values set by configure.

In the makefile, this renames the variables that used to be $XXFLAGS to
$PY_XXFLAGS, and renames the old $PY_CFLAGS to $PY_CORE_CFLAGS.  To compensate,
sysconfig now aliases $XXFLAGS=$PY_XXFLAGS so that scripts using it keep
working.  I see that as the right interface, not a backward-compatibility hack,
since these are logically the $XXFLAGS variables; we just use a different name
in the makefile to deal with make's semantics.

Lib/sysconfig.py

@@ -259,6 +259,11 @@ def _parse_makefile(filename, vars=None):
                 # bogus variable reference; just drop it since we can't deal
                 variables.remove(name)
 
+    # Add in CFLAGS, LDFLAGS, and CPPFLAGS, which are named with a
+    # prefix in the Makefile.
+    for var in ('CFLAGS', 'LDFLAGS', 'CPPFLAGS'):
+        done[var] = done['PY_' + var]
+
     # save the results in the global dictionary
     vars.update(done)
     return vars

Makefile.pre.in

@@ -59,12 +59,18 @@ MAKESETUP=      $(srcdir)/Modules/makesetup
 # Compiler options
 OPT=		@OPT@
 BASECFLAGS=	@BASECFLAGS@
-CFLAGS=		$(BASECFLAGS) @CFLAGS@ $(OPT) $(EXTRA_CFLAGS)
+CONFIGURE_CFLAGS=	@CFLAGS@
+CONFIGURE_CPPFLAGS=	@CPPFLAGS@
+CONFIGURE_LDFLAGS=	@LDFLAGS@
+# Avoid assigning CFLAGS, LDFLAGS, etc. so users can use them on the
+# command line to append to these values without stomping the pre-set
+# values.
+PY_CFLAGS=	$(BASECFLAGS) $(OPT) $(CONFIGURE_CFLAGS) $(CFLAGS) $(EXTRA_CFLAGS)
 # Both CPPFLAGS and LDFLAGS need to contain the shell's value for setup.py to
 # be able to build extension modules using the directories specified in the
 # environment variables
-CPPFLAGS=	-I. -IInclude -I$(srcdir)/Include @CPPFLAGS@
-LDFLAGS=	@LDFLAGS@
+PY_CPPFLAGS=	-I. -IInclude -I$(srcdir)/Include $(CONFIGURE_CPPFLAGS) $(CPPFLAGS)
+PY_LDFLAGS=	$(CONFIGURE_LDFLAGS) $(LDFLAGS)
 LDLAST=		@LDLAST@
 SGI_ABI=	@SGI_ABI@
 CCSHARED=	@CCSHARED@
@@ -73,7 +79,7 @@ ARFLAGS=	@ARFLAGS@
 # Extra C flags added for building the interpreter object files.
 CFLAGSFORSHARED=@CFLAGSFORSHARED@
 # C flags used for building the interpreter object files
-PY_CFLAGS=	$(CFLAGS) $(CPPFLAGS) $(CFLAGSFORSHARED) -DPy_BUILD_CORE
+PY_CORE_CFLAGS=	$(PY_CFLAGS) $(PY_CPPFLAGS) $(CFLAGSFORSHARED) -DPy_BUILD_CORE
 
 
 # Machine-dependent subdirectories
@@ -411,7 +417,7 @@ coverage:
 
 # Build the interpreter
 $(BUILDPYTHON):	Modules/python.o $(LIBRARY) $(LDLIBRARY)
-		$(LINKCC) $(LDFLAGS) $(LINKFORSHARED) -o $@ \
+		$(LINKCC) $(PY_LDFLAGS) $(LINKFORSHARED) -o $@ \
 			Modules/python.o \
 			$(BLDLIBRARY) $(LIBS) $(MODLIBS) $(SYSLIBS) $(LDLAST)
 
@@ -422,8 +428,8 @@ platform: $(BUILDPYTHON)
 # Build the shared modules
 sharedmods: $(BUILDPYTHON)
 	@case $$MAKEFLAGS in \
-	*s*) $(RUNSHARED) CC='$(CC)' LDSHARED='$(BLDSHARED)' LDFLAGS='$(LDFLAGS)' OPT='$(OPT)' ./$(BUILDPYTHON) -E $(srcdir)/setup.py -q build;; \
-	*) $(RUNSHARED) CC='$(CC)' LDSHARED='$(BLDSHARED)' LDFLAGS='$(LDFLAGS)' OPT='$(OPT)' ./$(BUILDPYTHON) -E $(srcdir)/setup.py build;; \
+	*s*) $(RUNSHARED) CC='$(CC)' LDSHARED='$(BLDSHARED)' LDFLAGS='$(PY_LDFLAGS)' OPT='$(OPT)' ./$(BUILDPYTHON) -E $(srcdir)/setup.py -q build;; \
+	*) $(RUNSHARED) CC='$(CC)' LDSHARED='$(BLDSHARED)' LDFLAGS='$(PY_LDFLAGS)' OPT='$(OPT)' ./$(BUILDPYTHON) -E $(srcdir)/setup.py build;; \
 	esac
 
 # Build static library
@@ -440,18 +446,18 @@ $(LIBRARY): $(LIBRARY_OBJS)
 
 libpython$(VERSION).so: $(LIBRARY_OBJS)
 	if test $(INSTSONAME) != $(LDLIBRARY); then \
-		$(LDSHARED) $(LDFLAGS) -Wl,-h$(INSTSONAME) -o $(INSTSONAME) $(LIBRARY_OBJS) $(MODLIBS) $(SHLIBS) $(LIBC) $(LIBM) $(LDLAST); \
+		$(LDSHARED) $(PY_LDFLAGS) -Wl,-h$(INSTSONAME) -o $(INSTSONAME) $(LIBRARY_OBJS) $(MODLIBS) $(SHLIBS) $(LIBC) $(LIBM) $(LDLAST); \
 		$(LN) -f $(INSTSONAME) $@; \
 	else \
-		$(LDSHARED) $(LDFLAGS) -o $@ $(LIBRARY_OBJS) $(MODLIBS) $(SHLIBS) $(LIBC) $(LIBM) $(LDLAST); \
+		$(LDSHARED) $(PY_LDFLAGS) -o $@ $(LIBRARY_OBJS) $(MODLIBS) $(SHLIBS) $(LIBC) $(LIBM) $(LDLAST); \
 	fi
 
 libpython$(VERSION).dylib: $(LIBRARY_OBJS)
-	 $(CC) -dynamiclib -Wl,-single_module $(LDFLAGS) -undefined dynamic_lookup -Wl,-install_name,$(prefix)/lib/libpython$(VERSION).dylib -Wl,-compatibility_version,$(VERSION) -Wl,-current_version,$(VERSION) -o $@ $(LIBRARY_OBJS) $(SHLIBS) $(LIBC) $(LIBM) $(LDLAST); \
+	 $(CC) -dynamiclib -Wl,-single_module $(PY_LDFLAGS) -undefined dynamic_lookup -Wl,-install_name,$(prefix)/lib/libpython$(VERSION).dylib -Wl,-compatibility_version,$(VERSION) -Wl,-current_version,$(VERSION) -o $@ $(LIBRARY_OBJS) $(SHLIBS) $(LIBC) $(LIBM) $(LDLAST); \
 		 
 
 libpython$(VERSION).sl: $(LIBRARY_OBJS)
-	$(LDSHARED) $(LDFLAGS) -o $@ $(LIBRARY_OBJS) $(MODLIBS) $(SHLIBS) $(LIBC) $(LIBM) $(LDLAST)
+	$(LDSHARED) $(PY_LDFLAGS) -o $@ $(LIBRARY_OBJS) $(MODLIBS) $(SHLIBS) $(LIBC) $(LIBM) $(LDLAST)
 
 # Copy up the gdb python hooks into a position where they can be automatically
 # loaded by gdb during Lib/test/test_gdb.py
@@ -497,7 +503,7 @@ $(PYTHONFRAMEWORKDIR)/Versions/$(VERSION)/$(PYTHONFRAMEWORK): \
 # for a shared core library; otherwise, this rule is a noop.
 $(DLLLIBRARY) libpython$(VERSION).dll.a: $(LIBRARY_OBJS)
 	if test -n "$(DLLLIBRARY)"; then \
-		$(LDSHARED) $(LDFLAGS) -Wl,--out-implib=$@ -o $(DLLLIBRARY) $^ \
+		$(LDSHARED) $(PY_LDFLAGS) -Wl,--out-implib=$@ -o $(DLLLIBRARY) $^ \
 			$(LIBS) $(MODLIBS) $(SYSLIBS) $(LDLAST); \
 	else true; \
 	fi
@@ -541,10 +547,10 @@ Modules/getbuildinfo.o: $(PARSER_OBJS) \
 		$(SIGNAL_OBJS) \
 		$(MODOBJS) \
 		$(srcdir)/Modules/getbuildinfo.c
-	$(CC) -c $(PY_CFLAGS) -DSVNVERSION="\"`LC_ALL=C $(SVNVERSION)`\"" -o $@ $(srcdir)/Modules/getbuildinfo.c
+	$(CC) -c $(PY_CORE_CFLAGS) -DSVNVERSION="\"`LC_ALL=C $(SVNVERSION)`\"" -o $@ $(srcdir)/Modules/getbuildinfo.c
 
 Modules/getpath.o: $(srcdir)/Modules/getpath.c Makefile
-	$(CC) -c $(PY_CFLAGS) -DPYTHONPATH='"$(PYTHONPATH)"' \
+	$(CC) -c $(PY_CORE_CFLAGS) -DPYTHONPATH='"$(PYTHONPATH)"' \
 		-DPREFIX='"$(prefix)"' \
 		-DEXEC_PREFIX='"$(exec_prefix)"' \
 		-DVERSION='"$(VERSION)"' \
@@ -552,7 +558,7 @@ Modules/getpath.o: $(srcdir)/Modules/getpath.c Makefile
 		-o $@ $(srcdir)/Modules/getpath.c
 
 Modules/python.o: $(srcdir)/Modules/python.c
-	$(MAINCC) -c $(PY_CFLAGS) -o $@ $(srcdir)/Modules/python.c
+	$(MAINCC) -c $(PY_CORE_CFLAGS) -o $@ $(srcdir)/Modules/python.c
 
 $(IO_OBJS): $(IO_H)
 
@@ -561,7 +567,7 @@ $(GRAMMAR_H) $(GRAMMAR_C): $(PGEN) $(GRAMMAR_INPUT)
 		-$(PGEN) $(GRAMMAR_INPUT) $(GRAMMAR_H) $(GRAMMAR_C)
 
 $(PGEN):	$(PGENOBJS)
-		$(CC) $(OPT) $(LDFLAGS) $(PGENOBJS) $(LIBS) -o $(PGEN)
+		$(CC) $(OPT) $(PY_LDFLAGS) $(PGENOBJS) $(LIBS) -o $(PGEN)
 
 Parser/grammar.o:	$(srcdir)/Parser/grammar.c \
 				$(srcdir)/Include/token.h \
@@ -581,10 +587,10 @@ $(AST_C): $(AST_ASDL) $(ASDLGEN_FILES)
 Python/compile.o Python/symtable.o Python/ast.o: $(GRAMMAR_H) $(AST_H)
 
 Python/getplatform.o: $(srcdir)/Python/getplatform.c
-		$(CC) -c $(PY_CFLAGS) -DPLATFORM='"$(MACHDEP)"' -o $@ $(srcdir)/Python/getplatform.c
+		$(CC) -c $(PY_CORE_CFLAGS) -DPLATFORM='"$(MACHDEP)"' -o $@ $(srcdir)/Python/getplatform.c
 
 Python/importdl.o: $(srcdir)/Python/importdl.c
-		$(CC) -c $(PY_CFLAGS) -I$(DLINCLDIR) -o $@ $(srcdir)/Python/importdl.c
+		$(CC) -c $(PY_CORE_CFLAGS) -I$(DLINCLDIR) -o $@ $(srcdir)/Python/importdl.c
 
 Objects/unicodectype.o:	$(srcdir)/Objects/unicodectype.c \
 				$(srcdir)/Objects/unicodetype_db.h
@@ -1130,7 +1136,7 @@ config.status:	$(srcdir)/configure
 
 # Some make's put the object file in the current directory
 .c.o:
-	$(CC) -c $(PY_CFLAGS) -o $@ $<
+	$(CC) -c $(PY_CORE_CFLAGS) -o $@ $<
 
 # Run reindent on the library
 reindent:

Misc/NEWS

@@ -1530,6 +1530,12 @@ Extension Modules
 Build
 -----
 
+- Issue #9189: Make a user-specified CFLAGS, CPPFLAGS, or LDFLAGS
+  setting override the configure and makefile defaults, without
+  deleting options the user didn't intend to override.  Developers
+  should no longer need to specify OPT or EXTRA_CFLAGS, although those
+  variables are still present for backward-compatibility.
+
 - Issue #8854: Fix finding Visual Studio 2008 on Windows x64.
 
 - Issue #1759169, #8864: Drop _XOPEN_SOURCE on Solaris, define it for

Modules/makesetup

@@ -219,7 +219,7 @@ sed -e 's/[ 	]*#.*//' -e '/^[ 	]*$/d' |
 			case $doconfig in
 			no)	cc="$cc \$(CCSHARED) \$(CFLAGS) \$(CPPFLAGS)";;
 			*)
-				cc="$cc \$(PY_CFLAGS)";;
+				cc="$cc \$(PY_CORE_CFLAGS)";;
 			esac
 			rule="$obj: $src; $cc $cpps -c $src -o $obj"
 			echo "$rule" >>$rulesf

configure

@@ -1929,11 +1929,11 @@ else
        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 $ac_includes_default
+	     enum { N = $2 / 2 - 1 };
 int
 main ()
 {
-static int test_array [1 - 2 * !(enum { N = $2 / 2 - 1 };
-	     0 < ($ac_type) ((((($ac_type) 1 << N) << N) - 1) * 2 + 1))];
+static int test_array [1 - 2 * !(0 < ($ac_type) ((((($ac_type) 1 << N) << N) - 1) * 2 + 1))];
 test_array [0] = 0
 
   ;
@@ -1944,11 +1944,11 @@ if ac_fn_c_try_compile "$LINENO"; then :
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 $ac_includes_default
+	        enum { N = $2 / 2 - 1 };
 int
 main ()
 {
-static int test_array [1 - 2 * !(enum { N = $2 / 2 - 1 };
-		($ac_type) ((((($ac_type) 1 << N) << N) - 1) * 2 + 1)
+static int test_array [1 - 2 * !(($ac_type) ((((($ac_type) 1 << N) << N) - 1) * 2 + 1)
 		 < ($ac_type) ((((($ac_type) 1 << N) << N) - 1) * 2 + 2))];
 test_array [0] = 0
 
@@ -3158,9 +3158,12 @@ then
 (it is also a good idea to do 'make clean' before compiling)" "$LINENO" 5
 fi
 
-# If the user set CFLAGS, use this instead of the automatically
-# determined setting
-preset_cflags="$CFLAGS"
+# Don't let AC_PROG_CC set the default CFLAGS. It normally sets -g -O2
+# when the compiler supports them, but we don't always want -O2, and
+# we set -g later.
+if test -z "$CFLAGS"; then
+        CFLAGS=
+fi
 ac_ext=c
 ac_cpp='$CPP $CPPFLAGS'
 ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
@@ -3952,10 +3955,6 @@ ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
 ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
 ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
-if test ! -z "$preset_cflags"
-then
-	CFLAGS=$preset_cflags
-fi
 
 
 

configure.in

@@ -461,14 +461,13 @@ then
 (it is also a good idea to do 'make clean' before compiling)])
 fi
 
-# If the user set CFLAGS, use this instead of the automatically
-# determined setting
-preset_cflags="$CFLAGS"
-AC_PROG_CC
-if test ! -z "$preset_cflags"
-then
-	CFLAGS=$preset_cflags
+# Don't let AC_PROG_CC set the default CFLAGS. It normally sets -g -O2
+# when the compiler supports them, but we don't always want -O2, and
+# we set -g later.
+if test -z "$CFLAGS"; then
+        CFLAGS=
 fi
+AC_PROG_CC
 
 AC_SUBST(CXX)
 AC_SUBST(MAINCC)