The simple answer is to use strtoul() instead. The longer answer is that even if all you needed was signed 32 bit integers or were happy with 31 bits for unsigned, the atoi() function is a poor fit for what you appear to be doing. As you have already noted, the atoi() function converts a … Read more
The std::from_chars function does not throw, it only returns a value of type from_chars_result which is a struct with two fields: struct from_chars_result { const char* ptr; std::errc ec; }; You should inspect the values of ptr and ec when the function returns: #include <iostream> #include <string> #include <charconv> int main() { int i3; std::string_view … Read more
Use strtoull if you have it or _strtoui64() with visual studio. unsigned long long strtoull(const char *restrict str, char **restrict endptr, int base); /* I am sure MS had a good reason not to name it “strtoull” or * “_strtoull” at least. */ unsigned __int64 _strtoui64( const char *nptr, char **endptr, int base );
Try to use strtol(): strtol(“FA”, NULL, 16);
The proper function (as long as you are insisting on using C-style functions) is strtol and the conversion code might look as follows const char *number = “10”; /* for example */ char *end; long value = strtol(number, &end, 10); if (end == number || *end != ‘\0’ || errno == ERANGE) /* ERROR, abort … Read more
You have to include stdlib.h #include <stdlib.h> Next time you encounter similar warnings just run man atoi and the manual pages should state that which header file should be included.
That’s one of the reasons atoi is sometimes considered unsafe. Use strtol / strtoul instead. And if you have it use strtonum. The function atoi is more dangerous than you might think. The POSIX standard says: If the value cannot be represented, the behavior is undefined. The C99 standard says this also: 7.20.1 The functions … Read more
1). Are there any other differences between the two? I find std::atoi() a horrible function: It returns zero on error. If you consider zero as a valid input, then you cannot tell whether there was an error during the conversion or the input was zero. That’s just bad. See for example How do I tell … Read more
You have 3 choices: atoi This is probably the fastest if you’re using it in performance-critical code, but it does no error reporting. If the string does not begin with an integer, it will return 0. If the string contains junk after the integer, it will convert the initial part and ignore the rest. If … Read more
It means Ascii to Integer. Likewise, you can have atol for Ascii to Long, atof for Ascii to Float, etc. A Google search for ‘atoi “ascii to integer”‘ confirms this on several pages. I’m having trouble finding any official source on it… but in this listing of man pages from Third Edition Unix (1973) collected … Read more