On 2014-02-28 20:12:27 +0200, Martin Storsjö wrote:
> Without this cast, the BE_32() expression is sign extended when
> assigned to an uint64_t, since the uint8_t|uint8_t expression
> is promoted to an int.
>
> Also avoid undefined behaviour when left shifting an uint8_t
> by 24 by casting it to an uint32_t explicitly before shifting.
>
> Based on a patch by Michael Niedermayer.
> ---
> Casting the first uint8_t to an uint32_t before shifting,
> as suggested by Janne.
> ---
> tools/qt-faststart.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/tools/qt-faststart.c b/tools/qt-faststart.c
> index 634bb6d..027f806 100644
> --- a/tools/qt-faststart.c
> +++ b/tools/qt-faststart.c
> @@ -41,10 +41,10 @@
>
> #define BE_16(x) ((((uint8_t*)(x))[0] << 8) | ((uint8_t*)(x))[1])
>
> -#define BE_32(x) ((((uint8_t*)(x))[0] << 24) | \
> - (((uint8_t*)(x))[1] << 16) | \
> - (((uint8_t*)(x))[2] << 8) | \
> - ((uint8_t*)(x))[3])
> +#define BE_32(x) (((uint32_t)(((uint8_t*)(x))[0]) << 24) | \
> + (((uint8_t*)(x))[1] << 16) | \
> + (((uint8_t*)(x))[2] << 8) | \
> + ((uint8_t*)(x))[3])
>
> #define BE_64(x) (((uint64_t)(((uint8_t*)(x))[0]) << 56) | \
> ((uint64_t)(((uint8_t*)(x))[1]) << 48) | \
> @@ -123,7 +123,7 @@ int main(int argc, char *argv[])
> if (fread(atom_bytes, ATOM_PREAMBLE_SIZE, 1, infile) != 1) {
> break;
> }
> - atom_size = (uint32_t) BE_32(&atom_bytes[0]);
> + atom_size = BE_32(&atom_bytes[0]);
> atom_type = BE_32(&atom_bytes[4]);
>
> /* keep ftyp atom */
ok
Janne
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