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…loc.c)
The final loop of zend_mm_gc() walks the pages of each chunk, and dispatches
on the page map entry to decide how far to advance:
if (info & ZEND_MM_IS_SRUN) {
...
i += bin_pages[bin_num];
} else /* if (info & ZEND_MM_IS_LRUN) */ {
i += ZEND_MM_LRUN_PAGES(info);
}
This is the same "reach the large-run case by elimination" pattern that
0c87849 promoted to a real check in zend_mm_free_heap(), zend_mm_size() and
zend_mm_realloc_heap(), except this one was left behind. Promote the comment to
a ZEND_MM_CHECK() that requires both the ZEND_MM_IS_LRUN bit and a non-zero page
count before advancing, which guarantees forward progress and only fires on a
corrupted heap. It costs a test and a branch.
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…loc.c)
The final loop of zend_mm_gc() walks the pages of each chunk, and dispatches on the page map entry to decide how far to advance:
This is the same "reach the large-run case by elimination" pattern that 0c87849 promoted to a real check in zend_mm_free_heap(), zend_mm_size() and zend_mm_realloc_heap(), except this one was left behind. Promote the comment to a ZEND_MM_CHECK() that requires both the ZEND_MM_IS_LRUN bit and a non-zero page count before advancing, which guarantees forward progress and only fires on a corrupted heap. It costs a test and a branch.