Re: [PATCH] pack-bitmaps: plug memory leak, fix allocation size for recent_bitmaps

From: René Scharfe <l.s.r@web.de>
Date: May 19, 2015, 20:29 UTC
Message-ID: <555B9D1E.2050609@web.de>
In-Reply-To: <CAGZ79kZeX_VqcvTt_kgGKyWH0SV2zsV_j1KuxNhwR18zWfp5LA@mail.gmail.com>

Am 19.05.2015 um 02:57 schrieb Stefan Beller:

Show 16 quoted lines

> On Mon, May 18, 2015 at 4:24 PM, René Scharfe <l.s.r@web.de> wrote:
>> diff --git a/pack-bitmap.c b/pack-bitmap.c
>> index 62a98cc..e5abb8a 100644
>> --- a/pack-bitmap.c
>> +++ b/pack-bitmap.c
>> @@ -209,14 +209,12 @@ static inline uint8_t read_u8(const unsigned char *buffer, size_t *pos)
>>          return buffer[(*pos)++];
>>   }
>>
>> +#define MAX_XOR_OFFSET 160
>> +
>>   static int load_bitmap_entries_v1(struct bitmap_index *index)
>>   {
>> -       static const size_t MAX_XOR_OFFSET = 160;
>
> Is there a reason why we prefer defines over a  static const size_t here?

Yes, see below.

Show 6 quoted lines

>> -
>>          uint32_t i;
>> -       struct stored_bitmap **recent_bitmaps;
>> -
>> -       recent_bitmaps = xcalloc(MAX_XOR_OFFSET, sizeof(struct stored_bitmap));
>> +       struct stored_bitmap *recent_bitmaps[MAX_XOR_OFFSET] = { NULL };

If MAX_XOR_OFFSET is a const then C89 does not allow this declaration. C99 gives you a variable-length array here. VLAs can't be initialized at declaration time, so we'd need to add a memset() call (at least with GCC 4.9). Overall it's simpler and shorter to use a macro.

We could also use an enum, but that's not exactly common.

René