Synopsis

Detect and handle standard library errors.

Enabled by default

Yes

Severity/Certainty

High/High

Full description

The majority of the standard library functions, including I/O functions and memory allocation functions, return either a valid value or a value of the correct return type that indicates an error (for example, -1 or a null pointer). It is essential that programs detect and appropriately handle all errors in accordance with an error-handling policy. This check warns on usage of standard library functions without checking for errors in return value and/or errno.

Coding standards

Code examples

The following code example fails the check and will give a warning:

#include <locale.h>
#include <stdlib.h>

int utf8_to_wcs(wchar_t *wcs, size_t n, const char *utf8,
                size_t *size) {
    if (NULL == size) {
        return -1;
    }
    setlocale(LC_CTYPE, "en_US.UTF-8");
    *size = mbstowcs(wcs, utf8, n);
    return 0;
}

The following code example passes the check and will not give a warning about this issue:

#include <locale.h>
#include <stdlib.h>

int utf8_to_wcs(wchar_t *wcs, size_t n, const char *utf8,
                size_t *size) {
    if (NULL == size) {
        return -1;
    }
    const char *save = setlocale(LC_CTYPE, "en_US.UTF-8");
    if (NULL == save) {
        return -1;
    }

    *size = mbstowcs(wcs, utf8, n);

    if(*size == (size_t)(-1)) {
        /* handle error */
    }

    if (NULL == setlocale(LC_CTYPE, save)) {
        return -1;
    }
    return 0;
}