[ipxe-devel] [PATCH] [build] disable gcc stringop-truncation warnings

[Bruce Rogers]

The gcc 8 compiler introduces a warning for certain string manipulation
functions, flagging usages which _may_ not be intended. An audit of the
ipxe sources indicates all usages of strncat and strncpy are as intended,
so the warnings currently issues are not helpful, especially if warnings
are considered errors.

This patch adds detection of gcc's support for -Wno-stringop-truncation
to the build system, and if detected, uses that option to avoid the
warning.

Signed-off-by: Bruce Rogers <brogers at suse.com>
---
 src/Makefile.housekeeping | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/Makefile.housekeeping b/src/Makefile.housekeeping
index 00b07926..252a580f 100644
--- a/src/Makefile.housekeeping
+++ b/src/Makefile.housekeeping
@@ -131,6 +131,7 @@ eval :
 #
 
 WORKAROUND_CFLAGS :=
+WORKAROUND_HOST_CFLAGS :=
 WORKAROUND_ASFLAGS :=
 WORKAROUND_LDFLAGS :=
 
@@ -177,6 +178,14 @@ ifeq ($(CCTYPE),gcc)
 WNA_TEST = $(CC) -Wno-address -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 \
+	    >/dev/null 2>&1
+WNST_FLAGS := $(shell $(WNST_TEST) && $(ECHO) '-Wno-stringop-truncation')
+WORKAROUND_CFLAGS += $(WNST_FLAGS)
+WORKAROUND_HOST_CFLAGS += $(WNST_FLAGS)
 endif
 
 # Some versions of gas choke on division operators, treating them as
@@ -437,7 +446,7 @@ endif
 CFLAGS		+= $(WORKAROUND_CFLAGS) $(EXTRA_CFLAGS)
 ASFLAGS		+= $(WORKAROUND_ASFLAGS) $(EXTRA_ASFLAGS)
 LDFLAGS		+= $(WORKAROUND_LDFLAGS) $(EXTRA_LDFLAGS)
-HOST_CFLAGS	+= -O2 -g
+HOST_CFLAGS	+= $(WORKAROUND_HOST_CFLAGS) -O2 -g
 
 # Inhibit -Werror if NO_WERROR is specified on make command line
 #
-- 
2.16.3