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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 <suyj.fnst@cn.fujitsu.com>
[ 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@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Su Yanjun 2018-12-05 14:40:07 +08:00 committed by David Sterba
parent 737defd3a5
commit 07cead1a1e
2 changed files with 7 additions and 0 deletions
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5
Makefile
View File

@ -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)

2
Makefile.extrawarn
View File

@ -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