Build: Make compiler warnings configurable

Use the SR_ARG_ENABLE_WARNINGS macro to configure and check for
the availability of compiler warning flags. Maintain separate
sets of warning flags for C and C++.

The configure option --enable-warnings=[min|max|fatal|no] can
be used to set the compiler warning level for all languages.
The default level is "max".

Makefile.am

@@ -22,15 +22,15 @@ ACLOCAL_AMFLAGS = -I m4
 
 local_includes = -Iinclude -I$(srcdir)/include -I$(srcdir)/src -I.
 if BINDINGS_CXX
-local_includes += -Ibindings/cxx/include -I${srcdir}/bindings/cxx/include -Ibindings/cxx
+local_includes += -Ibindings/cxx/include -I$(srcdir)/bindings/cxx/include -Ibindings/cxx
 endif
 # Ensure that local include directories are always searched first.
 AM_CPPFLAGS = $(local_includes) -DFIRMWARE_DIR='"$(FIRMWARE_DIR)"'
 
 # The check CFLAGS are a superset of the libsigrok CFLAGS, and the
 # python bindings CFLAGS are a superset of the C++ bindings CFLAGS.
-AM_CFLAGS = $(CHECK_CFLAGS)
-AM_CXXFLAGS = $(PYSIGROK_CFLAGS)
+AM_CFLAGS = $(SR_WFLAGS) $(CHECK_CFLAGS)
+AM_CXXFLAGS = $(SR_WXXFLAGS) $(PYSIGROK_CFLAGS)
 
 lib_LTLIBRARIES = libsigrok.la
 

configure.ac

@@ -40,7 +40,6 @@ AH_BOTTOM([#endif /* SR_CONFIG_H */])
 # Enable more compiler warnings via -Wall and -Wextra. Add -fvisibility=hidden
 # and enforce use of SR_API to explicitly mark all public API functions.
 CFLAGS="$CFLAGS -std=c11"
-CFLAGS="$CFLAGS -Wall -Wextra -Wmissing-prototypes"
 CFLAGS="$CFLAGS -fvisibility=hidden"
 CFLAGS="$CFLAGS -D_POSIX_C_SOURCE=200112L"
 
@@ -150,6 +149,7 @@ SR_PKG_CHECK([check], [SR_PKGLIBS_CHECK], [check >= 0.9.4])
 AM_CONDITIONAL([HAVE_CHECK], [test "x$sr_have_check" = xyes])
 
 AC_LANG([C])
+SR_ARG_ENABLE_WARNINGS([SR_WFLAGS], [-Wall], [-Wall -Wextra -Wmissing-prototypes])
 
 # Check host characteristics.
 AC_C_BIGENDIAN
@@ -264,6 +264,7 @@ SR_DRIVER([ZEROPLUS Logic Cube], [zeroplus-logic-cube], [libusb])
 ###############################
 
 AC_LANG([C++])
+SR_ARG_ENABLE_WARNINGS([SR_WXXFLAGS], [-Wall], [-Wall -Wextra])
 
 AC_ARG_ENABLE([bindings],
 	[AS_HELP_STRING([--enable-bindings], [build language bindings [default=yes]])],
@@ -466,6 +467,8 @@ libsigrok configuration summary:
  - Prefix.......................... $prefix
  - Building on..................... $build
  - Building for.................... $host
+ - C compiler warnings............. $SR_WFLAGS
+ - C++ compiler warnings........... $SR_WXXFLAGS
 
 Detected libraries (required):
  - glib-2.0 >= 2.32.0.............. $sr_glib_version

m4/sigrok.m4

@@ -16,7 +16,7 @@
 ## You should have received a copy of the GNU General Public License
 ## along with sigrok. If not, see <http://www.gnu.org/licenses/>.
 
-#serial 20150821
+#serial 20150823
 
 ## SR_APPEND(var-name, [list-sep,] element)
 ##
@@ -125,9 +125,9 @@ m4_define([_SR_ARG_ENABLE_WARNINGS_ONCE],
 AC_PROVIDE([$0])[]dnl
 AC_ARG_ENABLE([warnings],
 		[AS_HELP_STRING([[--enable-warnings[=min|max|fatal|no]]],
-				[set compile pedantry level [default=min]])],
+				[set compile pedantry level [default=max]])],
 		[sr_enable_warnings=$enableval],
-		[sr_enable_warnings=min])[]dnl
+		[sr_enable_warnings=max])[]dnl
 dnl
 # Test whether the compiler accepts each flag.  Look at standard output,
 # since GCC only shows a warning message if an option is not supported.
@@ -173,9 +173,9 @@ int main(int argc, char** argv) { return (argv != 0) ? argc : 0; }
 ]])])
 AS_CASE([$sr_enable_warnings],
 	[no], [],
-	[max], [sr_check_compile_warning_flags $3],
+	[min], [sr_check_compile_warning_flags $2],
 	[fatal], [sr_check_compile_warning_flags $3 -Werror],
-	[sr_check_compile_warning_flags $2])
+	[sr_check_compile_warning_flags $3])
 rm -f "$sr_conftest"
 AC_SUBST([$1], [$sr_warning_flags])
 AC_MSG_RESULT([[$]{sr_warning_flags:-none}])[]dnl