Extract gcc version without running a test program

Change generation of print-gcc-version to preprocess, but not compile, a
dummy source file containing the macro GCC_VERSION, then scan the
resulting output to find the numeric value of the macro.  This lets the
compiler do the work of expanding the expression, but avoids running a
test program.  This is necessary for cross-compiler support, since
cross-compiled test outputs cannot be run locally.

Store the output in autogenerated-gcc-version, since it is not a
runnable program.

Author: Kevin Pyle

.gitignore

@@ -27,7 +27,6 @@ gcc-c-api/gcc-tree.h
 gcc-c-api/gcc-type.h
 gcc-c-api/gcc-variable.h
 gcc-with-python.1.gz
-print-gcc-version
 
 # Generated by Sphinx
 docs/_build

Makefile

@@ -62,7 +62,7 @@ PLUGIN_OBJECT_GENERATED_FILES:= $(patsubst %.c,%.o,$(PLUGIN_GENERATED_SOURCE_FIL
 PLUGIN_OBJECT_FILES:= $(PLUGIN_OBJECT_SOURCE_FILES) $(PLUGIN_OBJECT_GENERATED_FILES)
 GCCPLUGINS_DIR:= $(shell $(TARGET_GCC) --print-file-name=plugin)
 
-GENERATOR_DEPS=cpybuilder.py wrapperbuilder.py print-gcc-version
+GENERATOR_DEPS=cpybuilder.py wrapperbuilder.py autogenerated-gcc-version
 
 # The plugin supports both Python 2 and Python 3
 #
@@ -160,18 +160,20 @@ $(PLUGIN_OBJECT_GENERATED_FILES): CPPFLAGS+= $(if $(srcdir),-I$(srcdir))
 $(PLUGIN_OBJECT_SOURCE_FILES) $(PLUGIN_OBJECT_GENERATED_FILES): %.o: $(srcdir)%.c autogenerated-config.h $(srcdir)gcc-python.h $(LIBGCC_C_API_SO) autogenerated-EXTRA_CFLAGS.txt
 	$(COMPILE.c) $(shell cat autogenerated-EXTRA_CFLAGS.txt) $(OUTPUT_OPTION) $<
 
-print-gcc-version: print-gcc-version.c autogenerated-EXTRA_CFLAGS.txt
-	$(CC) \
-		$(CPPFLAGS) $(CFLAGS) \
-		$(shell cat autogenerated-EXTRA_CFLAGS.txt) \
-		-o $@ \
-		$<
+# Use a long variable name to avoid unwanted matches.  Add an explicit
+# -x c since gcc requires a language specifier when processing stdin.
+# C and C++ print the same version, so skip
+# autogenerated-EXTRA_CFLAGS.txt.
+autogenerated-gcc-version:
+	echo gcc_version_major_minor= __GNUC__ __GNUC_MINOR__ | \
+	$(TARGET_GCC) -x c -E - | \
+	{ awk '/^gcc_version_major_minor=/ { print ($$2*1000)+$$3; exit 0; }' > "$@.part" && test -s "$@.part" && mv -f "$@.part" "$@"; } || { rc=$$?; $(RM) "$@.part"; exit $$rc; }
 
 clean:
 	$(RM) *.so *.o gcc-c-api/*.o autogenerated*
 	$(RM) -r docs/_build
 	$(RM) -f gcc-with-$(PLUGIN_NAME).1 gcc-with-$(PLUGIN_NAME).1.gz
-	$(RM) -f print-gcc-version
+	$(RM) -f autogenerated-gcc-version
 	$(MAKE) -C gcc-c-api clean CC="$(CC)" TARGET_GCC="$(TARGET_GCC)"
 	find tests -name "*.o" -delete
 
@@ -283,7 +285,7 @@ demo: plugin
 json-examples: plugin
 	$(INVOCATION_ENV_VARS) $(srcdir)./gcc-with-cpychecker -I/usr/include/python2.7 -c libcpychecker_html/test/example1/bug.c
 
-test-suite: plugin print-gcc-version
+test-suite: plugin autogenerated-gcc-version
 	$(INVOCATION_ENV_VARS) $(PYTHON) run-test-suite.py
 
 show-ssa: plugin

gcc-python-plugin.spec

@@ -145,7 +145,7 @@ BuildPlugin() {
        PYTHON=$PythonExe \
        PYTHON_CONFIG=$PythonConfig \
        PLUGIN_PYTHONPATH=%{gcc_plugins_dir}/$PluginName \
-       plugin print-gcc-version
+       plugin autogenerated-gcc-version
     popd
 }
 

print-gcc-version.c

@@ -29,9 +29,9 @@
 PLUGIN_NAME = os.environ.get('PLUGIN_NAME', 'python')
 
 def get_gcc_version():
-    p = Popen(['./print-gcc-version'],
-              stdout=PIPE, stderr=PIPE)
-    out, err = p.communicate()
+    out = '0'
+    with open('autogenerated-gcc-version', 'r') as f:
+        out = f.read()
     return(int(out))
 
 GCC_VERSION = get_gcc_version()