Fix integer truncation in th_{tis2uni,uni2tis}_line #22
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The size_t n parameter was narrowed to an int left variable, which is wrong on 64-bit platforms, as callers expect min(n, strlen(s) + 1) result characters to be written (incl. the terminating NUL), yet, due to the truncation, at most n mod 2^31 characters are written, which may be 0, if n is size_t(INT_MAX) + . Fix by making the left variable also be of type size_t. This is safe, as each --left is protected by a left > 1 check, so the value can never become negative. We can't fix the return type, that would be incompatible with existing users, but users don't need the return value: it's easily calculated as min(n - 1, strlen(s)). Add a FIXME comment nonetheless, for when compatibility can be broken, and use saturation arithmetic instead of modular arithmetic to avoid the pseudo-random return value. Amend the documentation accordingly.
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The size_t n parameter was narrowed to an int left variable, which is wrong on 64-bit platforms, as callers expect min(n, strlen(s) + 1) result characters to be written (incl. the terminating NUL), yet, due to the truncation, at most n mod 2^31 characters are written, which may be 0, if n is size_t(INT_MAX) + .
Fix by making the left variable also be of type size_t. This is safe, as each --left is protected by a left > 1 check, so the value can never become negative.
We can't fix the return type, that would be incompatible with existing users, but users don't need the return value: it's easily calculated as min(n - 1, strlen(s)). Add a FIXME comment nonetheless, for when compatibility can be broken, and use saturation arithmetic instead of modular arithmetic to avoid the pseudo-random return value.
Amend the documentation accordingly.