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swscale/vscale: Increase type strictness

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libswscale/vscale.c makes extensive use of function pointers and in
doing so it converts these function pointers to and from a pointer to
void. Yet this is actually against the C standard:
C90 only guarantees that one can convert a pointer to any incomplete
type or object type to void* and back with the result comparing equal
to the original which makes pointers to void generic pointers to
incomplete or object type. Yet C90 lacks a generic function pointer
type.
C99 additionally guarantees that a pointer to a function of one type may
be converted to a pointer to a function of another type with the result
and the original comparing equal when converting back.
This makes any function pointer type a generic function pointer type.
Yet even this does not make pointers to void generic function pointers.

Both GCC and Clang emit warnings for this when in pedantic mode.

This commit fixes this by using a union that can hold one member of any
of the required function pointer types to store the function pointer.
This works even for C90.

Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
pull/336/head
Andreas Rheinhardt 5 years ago
parent 1dff97b7bc
commit 2fae000994
1 changed files with 29 additions and 22 deletions
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  1. 51
      libswscale/vscale.c

51
libswscale/vscale.c
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@ -25,7 +25,14 @@ typedef struct VScalerContext
int32_t *filter_pos;
int filter_size;
int isMMX;
void *pfn;
union {
yuv2planar1_fn yuv2planar1;
yuv2planarX_fn yuv2planarX;
yuv2interleavedX_fn yuv2interleavedX;
yuv2packed1_fn yuv2packed1;
yuv2packed2_fn yuv2packed2;
yuv2anyX_fn yuv2anyX;
} pfn;
yuv2packedX_fn yuv2packedX;
} VScalerContext;
@ -43,9 +50,9 @@ static int lum_planar_vscale(SwsContext *c, SwsFilterDescriptor *desc, int slice
uint16_t *filter = inst->filter[0] + (inst->isMMX ? 0 : sliceY * inst->filter_size);
if (inst->filter_size == 1)
((yuv2planar1_fn)inst->pfn)((const int16_t*)src[0], dst[0], dstW, c->lumDither8, 0);
inst->pfn.yuv2planar1((const int16_t*)src[0], dst[0], dstW, c->lumDither8, 0);
else
((yuv2planarX_fn)inst->pfn)(filter, inst->filter_size, (const int16_t**)src, dst[0], dstW, c->lumDither8, 0);
inst->pfn.yuv2planarX(filter, inst->filter_size, (const int16_t**)src, dst[0], dstW, c->lumDither8, 0);
if (desc->alpha) {
int sp = first - desc->src->plane[3].sliceY;
@ -55,9 +62,9 @@ static int lum_planar_vscale(SwsContext *c, SwsFilterDescriptor *desc, int slice
uint16_t *filter = inst->filter[1] + (inst->isMMX ? 0 : sliceY * inst->filter_size);
if (inst->filter_size == 1)
((yuv2planar1_fn)inst->pfn)((const int16_t*)src[0], dst[0], dstW, c->lumDither8, 0);
inst->pfn.yuv2planar1((const int16_t*)src[0], dst[0], dstW, c->lumDither8, 0);
else
((yuv2planarX_fn)inst->pfn)(filter, inst->filter_size, (const int16_t**)src, dst[0], dstW, c->lumDither8, 0);
inst->pfn.yuv2planarX(filter, inst->filter_size, (const int16_t**)src, dst[0], dstW, c->lumDither8, 0);
}
return 1;
@ -85,13 +92,13 @@ static int chr_planar_vscale(SwsContext *c, SwsFilterDescriptor *desc, int slice
uint16_t *filter = inst->filter[0] + (inst->isMMX ? 0 : chrSliceY * inst->filter_size);
if (c->yuv2nv12cX) {
((yuv2interleavedX_fn)inst->pfn)(c, filter, inst->filter_size, (const int16_t**)src1, (const int16_t**)src2, dst1[0], dstW);
inst->pfn.yuv2interleavedX(c, filter, inst->filter_size, (const int16_t**)src1, (const int16_t**)src2, dst1[0], dstW);
} else if (inst->filter_size == 1) {
((yuv2planar1_fn)inst->pfn)((const int16_t*)src1[0], dst1[0], dstW, c->chrDither8, 0);
((yuv2planar1_fn)inst->pfn)((const int16_t*)src2[0], dst2[0], dstW, c->chrDither8, 3);
inst->pfn.yuv2planar1((const int16_t*)src1[0], dst1[0], dstW, c->chrDither8, 0);
inst->pfn.yuv2planar1((const int16_t*)src2[0], dst2[0], dstW, c->chrDither8, 3);
} else {
((yuv2planarX_fn)inst->pfn)(filter, inst->filter_size, (const int16_t**)src1, dst1[0], dstW, c->chrDither8, 0);
((yuv2planarX_fn)inst->pfn)(filter, inst->filter_size, (const int16_t**)src2, dst2[0], dstW, c->chrDither8, inst->isMMX ? (c->uv_offx2 >> 1) : 3);
inst->pfn.yuv2planarX(filter, inst->filter_size, (const int16_t**)src1, dst1[0], dstW, c->chrDither8, 0);
inst->pfn.yuv2planarX(filter, inst->filter_size, (const int16_t**)src2, dst2[0], dstW, c->chrDither8, inst->isMMX ? (c->uv_offx2 >> 1) : 3);
}
}
@ -125,13 +132,13 @@ static int packed_vscale(SwsContext *c, SwsFilterDescriptor *desc, int sliceY, i
if (c->yuv2packed1 && lum_fsize == 1 && chr_fsize == 1) { // unscaled RGB
((yuv2packed1_fn)inst->pfn)(c, (const int16_t*)*src0, (const int16_t**)src1, (const int16_t**)src2,
inst->pfn.yuv2packed1(c, (const int16_t*)*src0, (const int16_t**)src1, (const int16_t**)src2,
(const int16_t*)(desc->alpha ? *src3 : NULL), *dst, dstW, 0, sliceY);
} else if (c->yuv2packed1 && lum_fsize == 1 && chr_fsize == 2 &&
chr_filter[2 * chrSliceY + 1] + chr_filter[2 * chrSliceY] == 4096 &&
chr_filter[2 * chrSliceY + 1] <= 4096U) { // unscaled RGB
int chrAlpha = chr_filter[2 * chrSliceY + 1];
((yuv2packed1_fn)inst->pfn)(c, (const int16_t*)*src0, (const int16_t**)src1, (const int16_t**)src2,
inst->pfn.yuv2packed1(c, (const int16_t*)*src0, (const int16_t**)src1, (const int16_t**)src2,
(const int16_t*)(desc->alpha ? *src3 : NULL), *dst, dstW, chrAlpha, sliceY);
} else if (c->yuv2packed2 && lum_fsize == 2 && chr_fsize == 2 &&
lum_filter[2 * sliceY + 1] + lum_filter[2 * sliceY] == 4096 &&
@ -145,7 +152,7 @@ static int packed_vscale(SwsContext *c, SwsFilterDescriptor *desc, int sliceY, i
c->lumMmxFilter[3] = lum_filter[2 * sliceY] * 0x10001;
c->chrMmxFilter[2] =
c->chrMmxFilter[3] = chr_filter[2 * chrSliceY] * 0x10001;
((yuv2packed2_fn)inst->pfn)(c, (const int16_t**)src0, (const int16_t**)src1, (const int16_t**)src2, (const int16_t**)src3,
inst->pfn.yuv2packed2(c, (const int16_t**)src0, (const int16_t**)src1, (const int16_t**)src2, (const int16_t**)src3,
*dst, dstW, lumAlpha, chrAlpha, sliceY);
} else { // general RGB
if ((c->yuv2packed1 && lum_fsize == 1 && chr_fsize == 2) ||
@ -195,7 +202,7 @@ static int any_vscale(SwsContext *c, SwsFilterDescriptor *desc, int sliceY, int
desc->alpha ? desc->dst->plane[3].line[dp3] : NULL };
av_assert1(!c->yuv2packed1 && !c->yuv2packed2);
((yuv2anyX_fn)inst->pfn)(c, lum_filter + sliceY * lum_fsize,
inst->pfn.yuv2anyX(c, lum_filter + sliceY * lum_fsize,
(const int16_t**)src0, lum_fsize, chr_filter + sliceY * chr_fsize,
(const int16_t**)src1, (const int16_t**)src2, chr_fsize, (const int16_t**)src3, dst, dstW, sliceY);
@ -270,9 +277,9 @@ void ff_init_vscale_pfn(SwsContext *c,
chrCtx->isMMX = use_mmx;
--idx;
if (yuv2nv12cX) chrCtx->pfn = yuv2nv12cX;
else if (c->vChrFilterSize == 1) chrCtx->pfn = yuv2plane1;
else chrCtx->pfn = yuv2planeX;
if (yuv2nv12cX) chrCtx->pfn.yuv2interleavedX = yuv2nv12cX;
else if (c->vChrFilterSize == 1) chrCtx->pfn.yuv2planar1 = yuv2plane1;
else chrCtx->pfn.yuv2planarX = yuv2planeX;
}
lumCtx = c->desc[idx].instance;
@ -283,8 +290,8 @@ void ff_init_vscale_pfn(SwsContext *c,
lumCtx->filter_pos = c->vLumFilterPos;
lumCtx->isMMX = use_mmx;
if (c->vLumFilterSize == 1) lumCtx->pfn = yuv2plane1;
else lumCtx->pfn = yuv2planeX;
if (c->vLumFilterSize == 1) lumCtx->pfn.yuv2planar1 = yuv2plane1;
else lumCtx->pfn.yuv2planarX = yuv2planeX;
} else {
lumCtx = c->desc[idx].instance;
@ -303,12 +310,12 @@ void ff_init_vscale_pfn(SwsContext *c,
if (yuv2packedX) {
if (c->yuv2packed1 && c->vLumFilterSize == 1 && c->vChrFilterSize <= 2)
lumCtx->pfn = yuv2packed1;
lumCtx->pfn.yuv2packed1 = yuv2packed1;
else if (c->yuv2packed2 && c->vLumFilterSize == 2 && c->vChrFilterSize == 2)
lumCtx->pfn = yuv2packed2;
lumCtx->pfn.yuv2packed2 = yuv2packed2;
lumCtx->yuv2packedX = yuv2packedX;
} else
lumCtx->pfn = yuv2anyX;
lumCtx->pfn.yuv2anyX = yuv2anyX;
}
}

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