build: New configure --enable-coverage option

Some of the autoconf logic is originally from Asad. In addition, the
explicit call to __gcov_flush() is now vendored in vdef.h like other
toolchain abstractions.

.gitignore

@@ -125,6 +125,10 @@ cscope.*out
 /lib/libvarnishapi/vsl_glob_test
 /lib/libvarnishapi/vxp_test
 
+# GCOV droppings
+*.gcda
+*.gcno
+
 # vtc-bisect.sh default vtc
 /bisect.vtc
 

Makefile.am

@@ -42,6 +42,9 @@ install-data-local:
 	$(install_sh) -d -m 0755 $(DESTDIR)$(localstatedir)/varnish
 
 
+distclean-local:
+	find . '(' -name '*.gcda' -o -name '*.gcda' ')' -exec rm '{}' ';'
+
 distcleancheck_listfiles = \
 	find . -type f -exec sh -c 'test -f $(srcdir)/$$1 || echo $$1' \
 		sh '{}' ';'

bin/varnishd/cache/cache_panic.c

@@ -65,10 +65,6 @@
  *
  */
 
-#ifdef GCOVING
-    int __gcov_flush(void);
-#endif
-
 static struct vsb pan_vsb_storage, *pan_vsb;
 static pthread_mutex_t panicstr_mtx;
 
@@ -812,9 +808,7 @@ pan_ic(const char *func, const char *file, int line, const char *cond,
 	VSB_cat(pan_vsb, "\n");
 	VSB_putc(pan_vsb, '\0');	/* NUL termination */
 
-#ifdef GCOVING
-	__gcov_flush();
-#endif
+	v_gcov_flush();
 	abort();
 }
 

bin/varnishd/mgt/mgt_cli.c

@@ -63,10 +63,6 @@ static const struct cli_cmd_desc *cmds[] = {
 #include "tbl/cli_cmds.h"
 };
 
-#ifdef GCOVING
-    int __gcov_flush(void);
-#endif
-
 static const int ncmds = sizeof cmds / sizeof cmds[0];
 
 static int		cli_i = -1, cli_o = -1;
@@ -112,9 +108,7 @@ mcf_panic(struct cli *cli, const char * const *av, void *priv)
 	(void)cli;
 	(void)av;
 	(void)priv;
-#ifdef GCOVING
-	__gcov_flush();
-#endif
+	v_gcov_flush();
 	AZ(strcmp("", "You asked for it"));
 	/* NOTREACHED */
 	abort();

configure.ac

@@ -769,6 +769,13 @@ case $CFLAGS in
     ;;
 esac
 
+# --enable-coverage
+AC_ARG_ENABLE(coverage,
+	AS_HELP_STRING([--enable-coverage],
+		[enable coverage (implies debugging symbols, default is NO)]),
+	    [],
+	    [enable_coverage=no])
+
 # --enable-debugging-symbols
 AC_ARG_ENABLE(debugging-symbols,
 	AS_HELP_STRING([--enable-debugging-symbols],
@@ -776,6 +783,25 @@ AC_ARG_ENABLE(debugging-symbols,
 	    [],
 	    [enable_debugging_symbols=no])
 
+if test "$enable_coverage" != no; then
+	AC_DEFINE([GCOVING], [1], [Define to 1 if code coverage is enabled.])
+	save_CFLAGS=$CFLAGS
+	CFLAGS=
+	AX_CHECK_COMPILE_FLAG([--coverage],
+		[COV_FLAGS=--coverage],
+		[AX_CHECK_COMPILE_FLAG([-fprofile-arcs -ftest-coverage],
+			[COV_FLAGS="-fprofile-arcs -ftest-coverage"])])
+	AX_CHECK_COMPILE_FLAG([-fprofile-abs-path],
+		[COV_FLAGS="$COV_FLAGS -fprofile-abs-path"])
+	AX_CHECK_COMPILE_FLAG([-fPIC], [COV_FLAGS="$COV_FLAGS -fPIC"])
+	CFLAGS=$COV_FLAGS
+	AC_CHECK_FUNCS([__gcov_flush])
+	AC_CHECK_FUNCS([__gcov_dump])
+	AC_CHECK_FUNCS([__llvm_gcov_flush])
+	CFLAGS="$save_CFLAGS $COV_FLAGS"
+	enable_debugging_symbols=yes
+fi
+
 if test "$enable_debugging_symbols" != no; then
 	if test "x$SUNCC" = "xyes" ; then
 		CFLAGS="${CFLAGS} -O0 -g"

include/vdef.h

@@ -112,6 +112,19 @@
 #  define v_dont_optimize
 #endif
 
+#ifdef HAVE___GCOV_FLUSH
+#  define v_gcov_flush() __gcov_flush()
+int __gcov_flush(void);
+#elif defined HAVE___GCOV_DUMP
+#  define v_gcov_flush() __gcov_dump()
+void __gcov_dump(void);
+#elif defined HAVE___LLVM_GCOV_FLUSH
+#  define v_gcov_flush() __llvm_gcov_flush()
+int __llvm_gcov_flush(void);
+#else
+#  define v_gcov_flush() do { } while (0)
+#endif
+
 /*********************************************************************
  * Fundamental numerical limits
   * These limits track RFC8941