Fix unspecified behaviour in zend_alloc in heap->limit computation #12613
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Right-shifting a negative number is unspecified (i.e. implementation-defined) behaviour [1]. If we take a look at the generated assembly [2], we see that the wrong value is computed. Fix it by using Z_UL instead of Z_L. While we're at it, just change every occurrence of this pattern to use Z_UL instead of casting. [1] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1548.pdf §6.5.7.5 [2] https://godbolt.org/z/4Y1qKKjsh
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mvorisek
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Nov 5, 2023
iluuu1994
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Nov 6, 2023
Good catch, forgot about 32-bit for a second. |
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Right-shifting a negative number is unspecified (i.e. implementation-defined) behaviour [1]. If we take a look at the generated assembly [2], we see that the wrong value is computed. Fix it by using Z_UL instead of Z_L.
While we're at it, just change every occurrence of this pattern to use Z_UL instead of casting.
[1] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1548.pdf §6.5.7.5
[2] https://godbolt.org/z/4Y1qKKjsh