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cogl-flags: Fix iterating flag when the most-significant bit is set
When the flags contain a value that only has the most-significant bit set then ffsl will return the size of an unsigned long. According to the C spec it is undefined what happens when shifting by a number greater than or equal to the size of the left operand. On Intel (and probably others) this seems to end up being a no-op so the iteration breaks. To fix this we can split the shift into two separate shifts. We always need to shift by at least one bit so we can put this one bit shift into a separate operator. Reviewed-by: Robert Bragg <robert@linux.intel.com>
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@ -109,7 +109,12 @@ G_BEGIN_DECLS
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{ \
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int _next_bit = _cogl_util_ffsl (_mask); \
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(bit) += _next_bit; \
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_mask >>= _next_bit;
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/* This odd two-part shift is to avoid */ \
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/* shifting by sizeof (long)*8 which has */ \
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/* undefined results according to the */ \
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/* C spec (and seems to be a no-op in */ \
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/* practice) */ \
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_mask = (_mask >> (_next_bit - 1)) >> 1; \
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#define COGL_FLAGS_FOREACH_END \
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} } } G_STMT_END
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