[FFmpeg-devel] [PATCH] fix unused variable warning in libswscale

[Diego Biurrun]

On Tue, Nov 04, 2008 at 12:20:30AM +0100, Diego Biurrun wrote:
> Here is a small patch to eliminate an unused variable warning.

Since this simple change, seems to have generated a surprising amount of
questions, here are the two functions side-by-side, with the body of the
for loop omitted.

before:

static inline void RENAME(rgb24ToUV)(uint8_t *dstU, uint8_t *dstV, uint8_t *src1, uint8_t *src2, long width, uint32_t *unused)
{
    int i;
    assert(src1==src2);
#ifdef HAVE_MMX
    RENAME(bgr24ToUV_mmx)(dstU, dstV, src1, width, PIX_FMT_RGB24);
#else
    for (i=0; i<width; i++) {   
    }
#endif
}


after:

static inline void RENAME(rgb24ToUV)(uint8_t *dstU, uint8_t *dstV, uint8_t *src1, uint8_t *src2, long width, uint32_t *unused)
{
#ifdef HAVE_MMX
    assert(src1==src2);
    RENAME(bgr24ToUV_mmx)(dstU, dstV, src1, width, PIX_FMT_RGB24);
#else
    int i;
    assert(src1==src2);
    for (i=0; i<width; i++) {
    }
#endif
}


Yes, the assert is duplicated, but the alternative is to mix
declarations and statements if the variable declaration is placed below
the assert.  In any case the second alternative is more readable IMO
since you have two separate blocks and not intermingled preprocessor
statements.

Diego