autoconf: Add support for code coverage

Add support for code coverage collection. This helps
developers to check if their test scenarios really exercised
all the OpenOCD functionality that they intended to test.

- Option --enable-gcov has been added to configure.ac
  which enables the coverage collection using Gcov. (Disabled
  by default.)

- The steps to collect and inspect the coverage have been
  described in HACKING file.

Change-Id: I259e401937a255e7ad7f155359a0b7787e4d0752
Signed-off-by: Jan Matyas <jan.matyas@codasip.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/8521
Tested-by: jenkins
Reviewed-by: Evgeniy Naydanov <evgeniy.naydanov@syntacore.com>
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

.gitignore

@@ -15,6 +15,10 @@
 src/jtag/minidriver_imp.h
 src/jtag/jtag_minidriver.h
 
+# coverage files (gcov)
+*.gcda
+*.gcno
+
 # OpenULINK driver files generated by SDCC
 src/jtag/drivers/OpenULINK/*.rel
 src/jtag/drivers/OpenULINK/*.asm

HACKING

@@ -92,6 +92,22 @@ patch:
   make
   @endcode
 
+- Code coverage analysis
+
+  By inspecting the code coverage, you can identify potential gaps in your testing
+  and use that information to improve your test scenarios.
+
+  Example usage:
+  @code
+  mkdir build-gcov; cd build-gcov
+  ../configure --enable-gcov [...]
+  make
+  # ... Now execute your test scenarios to collect OpenOCD code coverage ...
+  lcov --capture --directory ./src --output-file openocd-coverage.info
+  genhtml openocd-coverage.info --output-directory coverage_report
+  # ... Open coverage_report/index.html in a web browser ...
+  @endcode
+
 Please consider performing these additional checks where appropriate
 (especially Clang Static Analyzer for big portions of new code) and
 mention the results (e.g. "Valgrind-clean, no new Clang analyzer

Makefile.am

@@ -38,6 +38,7 @@ endif
 
 # common flags used in openocd build
 AM_CFLAGS = $(GCC_WARNINGS)
+AM_LDFLAGS =
 
 AM_CPPFLAGS = $(HOST_CPPFLAGS)\
 			  -I$(top_srcdir)/src \
@@ -51,6 +52,12 @@ AM_CPPFLAGS += -I$(top_srcdir)/jimtcl \
 else
 AM_CPPFLAGS += $(JIMTCL_CFLAGS)
 endif
+
+if USE_GCOV
+AM_CFLAGS += --coverage
+AM_LDFLAGS += --coverage
+endif
+
 EXTRA_DIST += \
 	BUGS \
 	HACKING \

configure.ac

@@ -171,6 +171,9 @@ m4_define([DUMMY_ADAPTER],
 m4_define([OPTIONAL_LIBRARIES],
 	[[[capstone], [Use Capstone disassembly framework], []]])
 
+m4_define([COVERAGE],
+	[[[gcov], [Collect coverage using gcov], []]])
+
 AC_ARG_ENABLE([doxygen-html],
   AS_HELP_STRING([--disable-doxygen-html],
     [Disable building Doxygen manual as HTML.]),
@@ -199,6 +202,19 @@ AC_ARG_ENABLE([werror],
   AS_HELP_STRING([--disable-werror], [Do not treat warnings as errors]),
   [gcc_werror=$enableval], [gcc_werror=$gcc_warnings])
 
+AC_ARG_ENABLE([gcov],
+  AS_HELP_STRING([--enable-gcov], [Enable runtime coverage collection via gcov]),
+  [enable_gcov=$enableval], [enable_gcov=no])
+
+AS_IF([test "x$enable_gcov" = "xyes"], [
+  AC_DEFINE([USE_GCOV], [1], [1 to enable coverage collection using gcov.])
+  dnl When collecting coverage, disable optimizations.
+  dnl This overrides the "-O2" that autoconf uses by default:
+  CFLAGS+=" -O0"
+], [
+  AC_DEFINE([USE_GCOV], [0], [0 to leave coverage collection disabled.])
+])
+
 # set default verbose options, overridden by following options
 debug_usb_io=no
 debug_usb_comms=no
@@ -787,6 +803,8 @@ AM_CONDITIONAL([INTERNAL_JIMTCL], [test "x$use_internal_jimtcl" = "xyes"])
 AM_CONDITIONAL([HAVE_JIMTCL_PKG_CONFIG], [test "x$have_jimtcl_pkg_config" = "xyes"])
 AM_CONDITIONAL([INTERNAL_LIBJAYLINK], [test "x$use_internal_libjaylink" = "xyes"])
 
+AM_CONDITIONAL([USE_GCOV], [test "x$enable_gcov" = "xyes"])
+
 # Look for environ alternatives.  Possibility #1: is environ in unistd.h or stdlib.h?
 AC_MSG_CHECKING([for environ in unistd.h and stdlib.h])
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
@@ -862,7 +880,8 @@ m4_foreach([adapter], [USB1_ADAPTERS,
 	LIBGPIOD_ADAPTERS,
 	LIBJAYLINK_ADAPTERS, PCIE_ADAPTERS, SERIAL_PORT_ADAPTERS,
 	DUMMY_ADAPTER,
-	OPTIONAL_LIBRARIES],
+	OPTIONAL_LIBRARIES,
+	COVERAGE],
 	[s=m4_format(["%-40s"], ADAPTER_DESC([adapter]))
 	AS_CASE([$ADAPTER_VAR([adapter])],
 		[auto], [

src/openocd.c

@@ -375,6 +375,13 @@ int openocd_main(int argc, char *argv[])
 
 	log_exit();
 
+#if USE_GCOV
+	/* Always explicitly dump coverage data before terminating.
+	 * Otherwise coverage would not be dumped when exit_on_signal occurs. */
+	void __gcov_dump(void);
+	__gcov_dump();
+#endif
+
 	if (ret == ERROR_FAIL)
 		return EXIT_FAILURE;
 	else if (ret != ERROR_OK)