On Wed, Sep 28, 2011 at 04:06, James Felix Black <[email protected]> wrote:
> All,
>
> I have a chunk of code that creates an AVPicture from a raw stream of
> YUV420P, and rescales it. Easy-peasy, but I'm getting the error:
>
> zc_libav.c:29: error: passing argument 2 of ‘sws_scale’ from incompatible
> pointer type
>
> (I run -pedantic-errors when building test builds.)
For ffmpeg sources, -pedantic-errors report numerous complaints for me
(regarding C++ style comments, etc). But the "incompatible pointer
type" is reported with default warnings, too (my ver is 4.5.3). This
is the explanation: expected `const uint8_t * const*' but argument is
of type `uint8_t **'.
> Looking at libswscale/swscale.h, I see that the function signature is:
>
> int sws_scale(struct SwsContext *c, const uint8_t* const srcSlice[],
> const int srcStride[], int srcSliceY, int srcSliceH,
> uint8_t* const dst[], const int dstStride[]);
>
> My code (assume that in_pic and out_pic are properly generated AVPictures):
>
> sws_scale(sws_ctx,
> in_pic->data,
> in_pic->linesize,
> 0,
> in->y,
> out_pic->data,
> out_pic->linesize);
>
> I'm happy to cast that 'in_pic->data' to get the compiler to shut up, but I
> don't know how.
The fix is to cast this way:
(const uint8_t **)in_pic->data,
> If I turn off errors (-pedantic), it compiles and runs fine. So this is
> really about my neurotic need not to see warnings, I guess. But I'm still
> curious as to how someone with more C experience would handle this.
There is a breathtaking discussion of the subject here:
http://stackoverflow.com/questions/78125/why-cant-i-convert-char-to-a-const-char-const-in-c.
The bottom line is: it's just a problem in the C standard.
Sincerely,
Alex
> Am I doomed to special-casing this makefile rule to turn off
> -pedantic-errors? That would make me sad, but then again, there is much that
> makes me sad.
>
> TIA,
> ~ jfb
>
> --
> James Felix Black <[email protected]>
> "Some strangey that!"
> Words: http://homonculus.net
>
>
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>
>
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