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If control reaches the closing curly brace (}) of a non-void function without evaluating a return statement, using the return value of the function call is undefined behavior. (see See undefined behavior 88.).

Noncompliant Code Example

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This error is frequently diagnosed by compilers. (see See MSC00-C. Compile cleanly at high warning levels.).

Compliant Solution

This compliant solution ensures that the checkpass() function always returns a value:

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This compliant solution changes the interface of getlen() to store the result in a user-provided pointer and return returns a status indicator to report success or failure. The best method for handling this type of error is specific to the application and the type of error. (see See ERR00-C. Adopt and implement a consistent and comprehensive error-handling policy for more on error handling.).

#include <stddef.h>
 
int getlen(const int *input, size_t maxlen, int delim,
           size_t *result) {
  if (result == NULL) {
    return -1;
  }
  for (size_t i = 0; i < maxlen; ++i) {
    if (input[i] == delim) {
      *result = i;
      return 0;
    }
  }
  return -1;
}

void func(int userdata) {
  size_t i;
  int data[] = {1, 1, 1};
  if (getlen(data, sizeof(data), 0, &i) != 0) {
    /* Handle error */
  } else {
    data[i] = userdata;
  }
}

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