Re: [PATCH 1/2] dir.c: fix uninitialized memory warning

From: Pat Notz <patnotz@gmail.com>
Date: Sep 17, 2010, 00:32 UTC
Message-ID: <AANLkTin52McRcJcNocSGMxA7PUCiygSwQTHc1SWcMeOk@mail.gmail.com>
In-Reply-To: <AANLkTik1X0i-OYZCxokw-W3Kt+vEDtBvFeCwQU3q40ap@mail.gmail.com>

On Thu, Sep 16, 2010 at 5:26 PM, Nguyen Thai Ngoc Duy <pclouds@gmail.com> wrote:

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> 2010/9/17 Ævar Arnfjörð Bjarmason <avarab@gmail.com>:
>> On Thu, Sep 16, 2010 at 20:53, Pat Notz <patnotz@gmail.com> wrote:
>>> GCC 4.4.4 on MacOS warns about potential use of uninitialized memory.
>>>
>>> Signed-off-by: Pat Notz <patnotz@gmail.com>
>>> ---
>>>  dir.c |    2 +-
>>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/dir.c b/dir.c
>>> index 133f472..d1e5e5e 100644
>>> --- a/dir.c
>>> +++ b/dir.c
>>> @@ -232,7 +232,7 @@ int add_excludes_from_file_to_list(const char *fname,
>>>  {
>>>        struct stat st;
>>>        int fd, i;
>>> -       size_t size;
>>> +       size_t size = 0;
>>>        char *buf, *entry;
>>
>> What does the GCC warning say exactl? I.e. what line does it complain
>> about?

Here's the output:

make V=1 -j2 all gcc -o dir.o -c -g -O2 -Wall -I. -I/opt/local/include -DUSE_ST_TIMESPEC -DSHA1_HEADER='<openssl/sha.h>' -DNO_MEMMEM dir.c dir.c: In function 'add_excludes_from_file_to_list': dir.c:235: warning: 'size' may be used uninitialized in this function

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>>
>> Maybe this is a logic error introduced in v1.7.0-rc0~25^2? I haven't
>> checked.
>
> I don't see any case that "size" can be used uninitialized. Maybe the
> compiler was confused by
>
> if (!check_index ||
>    (buf = read_skip_worktree_file_from_index(fname, &size)) == NULL)
>        return -1;
>

No, line 245: if(size==0)

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> I wouldn't hurt though to initialize it early, even just to stop the
> compiler from complaining.
> --
> Duy
>