From: Su Yanjun <suyj.fnst@xxxxxxxxxxxxxx>
When using gcc8 + glibc 2.28.5 compiles utils.c, it complains as below:
utils.c:852:45: warning: '%s' directive output may be truncated writing
up to 4095 bytes into a region of size 4084 [-Wformat-truncation=]
snprintf(path, sizeof(path), "/dev/mapper/%s", name);
^~ ~~~~
In file included from /usr/include/stdio.h:873,
from utils.c:20:
/usr/include/bits/stdio2.h:67:10: note: '__builtin___snprintf_chk'
output between 13 and 4108 bytes into a destination of size 4096
return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
__bos (__s), __fmt, __va_arg_pack ());
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This isn't a type of warning we care about, particularly when calling
snprintf() we expect string to be truncated.
Using the GCC option -Wno-format-truncation to disable this for default
build and W=1 build, while still keep it for W=2/W=3 build.
Signed-off-by: Su Yanjun <suyj.fnst@xxxxxxxxxxxxxx>
[Use cc-disable-warning to fix the not working CFLAGS setting in configure.ac]
[Keep the warning in W=2/W=3 build]
Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
---
Makefile | 5 +++++
Makefile.extrawarn | 2 ++
2 files changed, 7 insertions(+)
diff --git a/Makefile b/Makefile
index f4ab14ea74c8..a9e57fecb6e6 100644
--- a/Makefile
+++ b/Makefile
@@ -62,6 +62,10 @@ DEBUG_LDFLAGS :=
ABSTOPDIR = $(shell pwd)
TOPDIR := .
+# Disable certain GCC 8 + glibc 2.28 warning for snprintf()
+# where string truncation for snprintf() is expected.
+DISABLE_WARNING_FLAGS := $(call cc-disable-warning, format-truncation)
+
# Common build flags
CFLAGS = $(SUBST_CFLAGS) \
$(CSTD) \
@@ -73,6 +77,7 @@ CFLAGS = $(SUBST_CFLAGS) \
-I$(TOPDIR) \
-I$(TOPDIR)/kernel-lib \
-I$(TOPDIR)/libbtrfsutil \
+ $(DISABLE_WARNING_FLAGS) \
$(EXTRAWARN_CFLAGS) \
$(DEBUG_CFLAGS_INTERNAL) \
$(EXTRA_CFLAGS)
diff --git a/Makefile.extrawarn b/Makefile.extrawarn
index 18a3a860053e..0c11f2450802 100644
--- a/Makefile.extrawarn
+++ b/Makefile.extrawarn
@@ -53,6 +53,7 @@ warning-1 += -Wold-style-definition
warning-1 += $(call cc-option, -Wmissing-include-dirs)
warning-1 += $(call cc-option, -Wunused-but-set-variable)
warning-1 += $(call cc-disable-warning, missing-field-initializers)
+warning-1 += $(call cc-disable-warning, format-truncation)
warning-2 := -Waggregate-return
warning-2 += -Wcast-align
@@ -61,6 +62,7 @@ warning-2 += -Wnested-externs
warning-2 += -Wshadow
warning-2 += $(call cc-option, -Wlogical-op)
warning-2 += $(call cc-option, -Wmissing-field-initializers)
+warning-2 += $(call cc-option, -Wformat-truncation)
warning-3 := -Wbad-function-cast
warning-3 += -Wcast-qual
--
2.19.2
