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btrfs-progs: fix seemly wrong format overflow warning

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[WARNING]
When compiling btrfs-progs, the following warning pops up:
  In file included from /usr/include/stdio.h:867,
                   from ./kerncompat.h:22,
                   from common/fsfeatures.c:17:
  In function 'printf',
      inlined from 'process_features' at common/fsfeatures.c:192:4,
      inlined from 'btrfs_process_runtime_features' at common/fsfeatures.c:205:2:
  /usr/include/bits/stdio2.h:107:10: warning: '%s' directive argument is null [-Wformat-overflow=]
    107 |   return __printf_chk (__USE_FORTIFY_LEVEL - 1, __fmt, __va_arg_pack ());
        |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This only occur with default make parameters. If compiling with D=1, the
warning just disappears.

The involved tool chain is:
- GCC 10.1.0

[CAUSE]
The offending code is:
  static void process_features(u64 flags, enum feature_source source)
  {
  ...
		if (flags & feat->flag) {
			printf("Turning ON incompat feature '%s': %s\n",
				feat->name, feat->desc);
		}
  ...
  }

Currently, there is no runtime/fs feature without a name nor
description.  So we shouldn't hit a feature with NULL as name nor
description.

This looks like a bug in GCC though.

[WORKAROUND]
However can workaround it by doing an explicit check on feat->name and
feat->desc to teach GCC not to do a wrong warning.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2020-06-23 13:48:04 +08:00 committed by David Sterba
parent ac75513621
commit 2eb48d8c81
1 changed files with 1 additions and 1 deletions
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2
common/fsfeatures.c
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@ -188,7 +188,7 @@ static void process_features(u64 flags, enum feature_source source)
for (i = 0; i < array_size; i++) {
const struct btrfs_feature *feat = get_feature(i, source);
if (flags & feat->flag) {
if (flags & feat->flag && feat->name && feat->desc) {
printf("Turning ON incompat feature '%s': %s\n",
feat->name, feat->desc);
}