MDEV-40176: UBSAN: runtime error: applying non-zero offset in my_charpos_mb#5291
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This pull request modifies the pointer arithmetic in the my_charpos_mb function within strings/ctype-mb.c to calculate (end-start)+2 instead of end+2-start, preventing potential undefined behavior from performing pointer arithmetic out of bounds. There are no review comments, and I have no feedback to provide.
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raghunandanbhat
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strings/ctype-mb.c:261my_charpos_mb
…rpos_mb` Problem: When `my_charpos_mb()` is called with pos = end = NULL and the string has fewer than `length` characters, the `end + 2 - start` return expression evaluates `end+2`, forming the pointer NULL+2. Offsetting a null pointer is undefined behavior. Fix: Compute the integer difference before adding the offset. The result is identical but no invalid pointer is ever formed.
…rpos_mb` (2) my_numchars_mb and my_charpos_mb both used their cs argument so remove the notused attribute on them.
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grooverdan
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Jun 29, 2026
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fixes MDEV-40176
Problem:
When
my_charpos_mb()is called with pos = end = NULL and the string has fewer thanlengthcharacters, theend + 2 - startreturn expression evaluatesend+2, forming the pointer NULL+2. Offsetting a null pointer is undefined behavior.Fix:
Compute the integer difference before adding the offset. The result is identical but no invalid pointer is ever formed.