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C does not portably expose string-to-float conversion errors

sebsite.pw 7 min read Editor score 6/10

The post examines how C’s `strtod` family uses `math_errhandling` to report overflow and why portable error checks are difficult. This is a useful reminder that standard-library behavior can vary across implementations.

What

Standard C string-to-float functions can report range errors through errno or floating-point exceptions, depending on math_errhandling.

How

Underflow reporting is optional in C; POSIX instead requires errno to be set for overflow and underflow.

Why it matters

Portable numeric parsers must account for implementation differences rather than relying on errno alone.

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