[build] Use positive-form tests when checking for supported warnings

Some versions of gcc seem to silently accept an attempt to disable an unrecognised warning (e.g. via -Wno-stringop-truncation) but will then report the unrecognised warning if any other error occurs during the build, resulting in a potentially misleading error message. Avoid this potential confusion by using the positive-form tests in order to determine the workaround CFLAGS. Signed-off-by: Michael Brown <mcb30@ipxe.org>
ipxe · Jul 8, 2018 · 1c47eb1 · 1c47eb1
1 parent 4095654
commit 1c47eb1
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/src/Makefile.housekeeping b/src/Makefile.housekeeping
@@ -174,14 +174,14 @@ endif
 # Inhibit this.
 #
 ifeq ($(CCTYPE),gcc)
-WNA_TEST = $(CC) -Wno-address -x c -c /dev/null -o /dev/null >/dev/null 2>&1
+WNA_TEST = $(CC) -Waddress -x c -c /dev/null -o /dev/null >/dev/null 2>&1
 WNA_FLAGS := $(shell $(WNA_TEST) && $(ECHO) '-Wno-address')
 WORKAROUND_CFLAGS += $(WNA_FLAGS)
 
 # gcc 8.0 generates warnings for certain suspect string operations. Our
 # sources have been vetted for correct usage.  Turn off these warnings.
 #
-WNST_TEST = $(CC) -Wno-stringop-truncation -x c -c /dev/null -o /dev/null \
+WNST_TEST = $(CC) -Wstringop-truncation -x c -c /dev/null -o /dev/null \
 		  >/dev/null 2>&1
 WNST_FLAGS := $(shell $(WNST_TEST) && $(ECHO) '-Wno-stringop-truncation')
 WORKAROUND_CFLAGS += $(WNST_FLAGS)