Convert char to unsigned before calling ctype.h functions #1
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the `isspace` and `isdigit` functions, like many other functions from ctype.h, actually take an `int` as the parameter, and are specified to have undefined behavior when the parameter is not in the range (-1)-255. Because it is implementation-defined whether `char` is signed or unsigned (and on most compilers targeting x86 it is actually signed), if a `char` in the range 128-254 (say, because the format string is encoded in a superset of ASCII, including UTF-8) is passed to those functions, it could be sign-extended to (-128)-(-2) and cause undefined behavior. This patch adds manually conversion from `char` to `unsigned char` before passing them to ctype.h functions; since `unsigned char`-to-`int` conversion is zero-extension, this avoids said undefined behavior.
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the
isspaceandisdigitfunctions, like many other functions from ctype.h, actually take anintas the parameter, and are specified to have undefined behavior when the parameter is not in the range (-1)-255. Because it is implementation-defined whethercharis signed or unsigned (and on most compilers targeting x86 it is actually signed), if acharin the range 128-254 (say, because the format string is encoded in a superset of ASCII, including UTF-8) is passed to those functions, it could be sign-extended to (-128)-(-2) and cause undefined behavior.This patch adds manually conversion from
chartounsigned charbefore passing them to ctype.h functions; sinceunsigned char-to-intconversion is zero-extension, this avoids said undefined behavior.