build-system: add clean-coverage target

This can be used to remove any stale coverage data before any
particular test run. This is useful for analysing individual tests.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>---

Makefile

@@ -723,6 +723,14 @@ module_block.h: $(SRC_PATH)/scripts/modules/module_block.py config-host.mak
 	$(addprefix $(SRC_PATH)/,$(patsubst %.mo,%.c,$(block-obj-m))), \
 	"GEN","$@")
 
+ifdef CONFIG_GCOV
+.PHONY: clean-coverage
+clean-coverage:
+	$(call quiet-command, \
+		find . \( -name '*.gcda' -o -name '*.gcov' \) -type f -exec rm {} +, \
+		"CLEAN", "coverage files")
+endif
+
 clean:
 # avoid old build problems by removing potentially incorrect old files
 	rm -f config.mak op-i386.h opc-i386.h gen-op-i386.h op-arm.h opc-arm.h gen-op-arm.h
@@ -1073,6 +1081,9 @@ endif
 		echo '')
 	@echo  'Cleaning targets:'
 	@echo  '  clean           - Remove most generated files but keep the config'
+ifdef CONFIG_GCOV
+	@echo  '  clean-coverage  - Remove coverage files'
+endif
 	@echo  '  distclean       - Remove all generated files'
 	@echo  '  dist            - Build a distributable tarball'
 	@echo  ''

docs/devel/testing.rst

@@ -161,9 +161,14 @@ GCC gcov support
 ``gcov`` is a GCC tool to analyze the testing coverage by
 instrumenting the tested code. To use it, configure QEMU with
 ``--enable-gcov`` option and build. Then run ``make check`` as usual.
-Reports can be obtained by running ``gcov`` command on the output
-files under ``$build_dir/tests/``, please read the ``gcov``
-documentation for more information.
+
+If you want to gather coverage information on a single test the ``make
+clean-coverage`` target can be used to delete any existing coverage
+information before running a single test.
+
+Reports can be obtained by running ``gcov`` command
+on the output files under ``$build_dir/tests/``, please read the
+``gcov`` documentation for more information.
 
 QEMU iotests
 ============