Fixed bug #76532 (excessive memory usage in mb_strimwidth)

[MarcusSchwarz]

No description provided.

[nikic]

This should use width or string->len, whichever is lower.

[nikic]

Merged as bf5a802 into 7.1+. Thanks!

[cmb69]

Is it really okay to rely on the zend_long to int conversion in the first place? To my knowledge, this is implementation defined behavior.

Also, the bug report claims that the issue occurs for $width > 2147483647, but the PHPT uses $width == 2147483647.

[nikic]

@cmb69 This PR fixes the issue of unnecessary over-allocation if the trim width exceeds the string length. The type conversion is a separate problem and already fixed in PHP 7.3 by the migration to size_t.

[cmb69]

@nikic Thanks! However, merging of the PR closed bug 76532 which is (also) about the integer overflow. For PHP 7.1 and 7.2, it might be sensible to check for width < 0 || width > INT_MAX) here,

[nikic]

@cmb69 This PR fixes the practical concern, and fully correct behavior is not possible on older versions, as the libmbfl support is not there. Making it fail nicer is IMHO a waste of time. However, feel free to add a check (just need to make sure it's not merged into master).