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The atoi family of functions should never be used for any purpose - they are broken by design. The reason why can be found in the C standard C23 7.24.1: The functions atof, atoi, atol, and atol...
Answer
#1: Initial revision
by
Lundin
·
2024-12-11T09:00:04Z (about 21 hours ago)
The `atoi` family of functions should never be used for any purpose - they are broken by design. The reason why can be found in the C standard C23 7.24.1: > The functions `atof`, `atoi`, `atol`, and `atoll` are not required to affect the value of the integer expression `errno` on an error. If the value of the result cannot be represented, the behavior is undefined. Meaning that the functions do not necessary have any error handling at all - if you pass a string which consists of other things than digit characters, anything can happen. Furthermore, the same chapter makes this guarantee (C23 7.24.2): > Except for the behavior on error, they are equivalent to > > atoi: (int)strtol(nptr, nullptr, 10) > atol: strtol(nptr, nullptr, 10) > atoll: strtoll(nptr, nullptr, 10) So the solution is to always use the `strtol` family of functions instead. They have error handling but are otherwise 100% equivalent to the `atoi` family, when passing base 10 = decimal as parameter. (In fact some of the better standard libraries implements `atoi` as a mere wrapper macro around `strtol`.)