[PATCH 2/9] btrfs-progs: fix gcc8 default build warning caused by '-Wformat-truncation'

[Qu Wenruo <wqu@suse.com>]

From: Su Yanjun <suyj.fnst@cn.fujitsu.com>

When using gcc8 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 PATH_MAX
is much less than either.

Using the GCC option -Wno-format-truncation to disable this for default
build.

Signed-off-by: Su Yanjun <suyj.fnst@cn.fujitsu.com>
[Use cc-disable-warning to fix the not working CFLAGS setting in configure.ac]
Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 Makefile           | 1 +
 Makefile.extrawarn | 1 +
 2 files changed, 2 insertions(+)

diff --git a/Makefile b/Makefile
index f4ab14ea74c8..252299f8869f 100644
--- a/Makefile
+++ b/Makefile
@@ -49,6 +49,7 @@ CSCOPE_CMD := cscope -u -b -c -q
 include Makefile.extrawarn
 
 EXTRA_CFLAGS :=
+EXTRA_CFLAGS += $(call cc-disable-warning, format-truncation)
 EXTRA_LDFLAGS :=
 
 DEBUG_CFLAGS_DEFAULT = -O0 -U_FORTIFY_SOURCE -ggdb3
diff --git a/Makefile.extrawarn b/Makefile.extrawarn
index 5849036fd166..bbb2d5173846 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
-- 
2.19.1