Messages in this thread | | | Date | Thu, 11 Feb 2016 09:06:37 -0500 | From | Theodore Ts'o <> | Subject | Re: [BUG REPORT] use of unreachable() masks uninitialized variables warnings |
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On Wed, Feb 10, 2016 at 08:13:09PM -0700, Jeff Merkey wrote: > Here are the sources of several bugs I have seen recently in ext4 I am > pretty sure with a null bh. One good check is to set the BUG() macro > NOT TO call unreachable() as a build test since the compiler will > ignore uninitialized variables in a function if someone calls BUG() > even conditionally, and never report them during build. > > The following are from v4.4.1 with a BUG() macro with the call to > unreachable() removed:
I checked all of the fs/ext4 warnings you listed and they are all false positives.
> In file included from fs/ext4/file.c:30:0: > fs/ext4/ext4_jbd2.h: In function ‘ext4_inode_journal_mode’: > fs/ext4/ext4_jbd2.h:409:1: warning: control reaches end of non-void > function [-Wreturn-type] > }
This is from a:
if (foo) { ... return foobie; } else if (bar) { ... return barbie; } else { BUG(); }
construct.
> fs/ext4/inode.c: In function ‘ext4_map_blocks’: > fs/ext4/inode.c:548:5: warning: ‘retval’ may be used uninitialized in > this function [-Wmaybe-uninitialized] > if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) { > ^ > fs/ext4/extents.c:2305:14: warning: ‘len’ may be used uninitialized in > this function [-Wmaybe-uninitialized] > ext4_lblk_t len; > ^
All of the may be used uninitialized warnings are from a:
if (foo) { ... retval = xxx; } else if (bar) { ... retval = yyy; } else { BUG(); }
construct.
It may be that there are some false warnings, but they certainly weren't from warnings you've listed from ext4.
Cheers,
- Ted
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