From 07cead1a1e2e244a94808555b1f5ae70995efbe9 Mon Sep 17 00:00:00 2001 From: Su Yanjun Date: Wed, 5 Dec 2018 14:40:07 +0800 Subject: [PATCH] btrfs-progs: silence build warning caused by gcc 8 '-Wformat-truncation' 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. Use the GCC option -Wno-format-truncation to disable this for default build and W=1 build, while still keeping it for W=2 and W=3 builds. Signed-off-by: Su Yanjun [ 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 Signed-off-by: David Sterba --- Makefile | 5 +++++ Makefile.extrawarn | 2 ++ 2 files changed, 7 insertions(+) diff --git a/Makefile b/Makefile index ee1fc139..29a4ee9e 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 9c88950e..e084ac61 100644 --- a/Makefile.extrawarn +++ b/Makefile.extrawarn @@ -52,6 +52,7 @@ 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 @@ -60,6 +61,7 @@ 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