SEI CERT C Coding Standard

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Comment: Added an example using strtoumax instead of scanf, which should be a portable solution, thus I removed the Windows example with scanf. It is perhaps a touch of a digression from the topic of this rec, namely formatted output, but it is a safer way to perform the conversion, and complies with our other recommendations regarding integer conversion.

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This compliant solution guarantees that a correct value in the range of mytypedef_t is read, or an error condition is detected, assuming the value of MYTYPEDEF_MAX is correct as the largest value representable by mytypedef_t:  We use the strtoumax function instead of scanf, as it provides enhanced error checking functionality.

Code Block
bgColor#ccccff
langc
#include <stdio.h>
#include <inttypes.h>
#inc #include <errno.h> 

mytypedef_t x;
uintmax_t temp;

/* ... */
if (fgets(buff, sizeof(buff), stdin) == NULL) {
  if (puts("EOF or read error\n") == EOF) {
    /* Handle error */
  }
} else {
  /* Check for errors in the conversion */
  errno = 0;
  temp = strtoumax(buff, &end_ptr, 10);
  if (ERANGE == errno) {
    if (puts("number out of range\n") == EOF) {
      /* Handle error */
    } 
  }
  else if (end_ptr == buff) {
    if (puts("not valid numeric input\n") == EOF) {
      /* Handle error */
    }
  }
  else if ('\n' != *end_ptr && '\0' != *end_ptr) {
    if (puts("extra characters on input line\n") == EOF) {
      /* Handle error */
    }
  }
  
  /* No conversion errors, attempt to store the converted value into x */
  if (temp > MYTYPEDEF_MAX) {
    /* Handle error */
  } else {
    x = temp;
  }
}

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