Add optional usage of gcov for test coverage

Use gcov to find how much code coverage our current testing gets. This
can be enabled by passing --with-gcov to configure and running "make
gcov". This is limited to gcc. Here's a run from the current code (for
some reason, gcov insists on profiling gstring.h).

/usr/bin/gcov pkg.h pkg.c parse.h parse.c main.c
File 'pkg.c'
Lines executed:73.16% of 611
pkg.c:creating 'pkg.c.gcov'

File '/usr/include/glib-2.0/glib/gstring.h'
Lines executed:100.00% of 6
/usr/include/glib-2.0/glib/gstring.h:creating 'gstring.h.gcov'

File 'parse.c'
Lines executed:79.67% of 492
parse.c:creating 'parse.c.gcov'

File 'main.c'
Lines executed:57.34% of 293
main.c:creating 'main.c.gcov'

.gitignore

@@ -6,6 +6,9 @@
 *.so
 *.exe
 *.orig
+*.gcda
+*.gcno
+*.gcov
 .deps/
 .libs/
 INSTALL

Makefile.am

@@ -24,6 +24,7 @@ endif
 
 AM_CFLAGS = \
 	$(WARN_CFLAGS) \
+	$(GCOV_CFLAGS) \
 	$(GLIB_CFLAGS)
 
 bin_PROGRAMS = pkg-config
@@ -42,6 +43,12 @@ dist_doc_DATA = pkg-config-guide.html
 dist_man_MANS = pkg-config.1
 EXTRA_DIST = README.win32
 
+# gcov test coverage
+gcov:
+	-$(MAKE) $(AM_MAKEFLAGS) -k check
+	$(GCOV) $(pkg_config_SOURCES)
+CLEANFILES = *.gcda *.gcno *.gcov
+
 # Since we can't always have glib in DIST_SUBDIRS, we need to make sure
 # glib is configured when we want to run dist. Unfortunately, there's no
 # DIST_CONFIGURE_FLAGS.

configure.ac

@@ -182,6 +182,27 @@ fi
 AC_SUBST(GLIB_LIBS)
 AC_SUBST(GLIB_CFLAGS)
 
+dnl
+dnl Optional gcov test coverage usage
+dnl
+AC_ARG_WITH([gcov],
+  [AS_HELP_STRING([--with-gcov], [gcov test coverage @<:@default=no@:>@])],
+  [],
+  [with_gcov=no])
+if test "x$with_gcov" = xyes; then
+  if test "$GCC" = no; then
+    AC_MSG_ERROR([gcov test coverage can only be used with GCC])
+  fi
+
+  AC_PATH_PROG([GCOV], [gcov], [AC_MSG_ERROR([could not find gcov program])])
+  GCOV_CFLAGS="-fprofile-arcs -ftest-coverage"
+
+  # Ensure there's no optimizing since last -O wins and CFLAGS is used
+  # at the end of COMPILE/LTCOMPILE.
+  CFLAGS="${CFLAGS+$CFLAGS }-O0"
+fi
+AC_SUBST([GCOV_CFLAGS])
+
 AC_CONFIG_FILES([
 Makefile
 check/Makefile