ERR33-C. Detect and handle standard library errors

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). Assuming that all calls to such functions will succeed and failing to check the return value for an indication of an error is a dangerous practice that may lead to unexpected or undefined behavior when an error occurs. It is essential that programs detect and appropriately handle all errors in accordance with an error-handling policy, as discussed in ERR00-C. Adopt and implement a consistent and comprehensive error-handling policy.

The successful completion or failure of each of the standard library functions listed in the following table shall be determined either by comparing the function’s return value with the value listed in the column labeled “Error Return” or by calling one of the library functions mentioned in the footnotes.

Standard Library Functions

Function	Successful Return	Error Return
`aligned_alloc()`	Pointer to space	`NULL`
`asctime_s()`	`0`	Nonzero
`at_quick_exit()`	`0`	Nonzero
`atexit()`	`0`	Nonzero
`bsearch()`	Pointer to matching element	`NULL`
`bsearch_s()`	Pointer to matching element	`NULL`
`btowc()`	Converted wide character	`WEOF`
`c16rtomb()`	Number of bytes	`(size_t)(-1)`
`c32rtomb()`	Number of bytes	`(size_t)(-1)`
`calloc()`	Pointer to space	`NULL`
`clock()`	Processor time	`(clock_t)(-1)`
`cnd_broadcast()`	`thrd_success`	`thrd_error`
`cnd_init()`	`thrd_success`	`thrd_nomem` or `thrd_error`
`cnd_signal()`	`thrd_success`	`thrd_error`
`cnd_timedwait()`	`thrd_success`	`thrd_timedout` or `thrd_error`
`cnd_wait()`	`thrd_success`	`thrd_error`
`ctime_s()`	`0`	Nonzero
`fclose()`	`0`	`EOF` (negative)
`fflush()`	`0`	`EOF` (negative)
`fgetc()`	Character read	`EOF`¹
`fgetpos()`	`0`	Nonzero, `errno > 0`
`fgets()`	Pointer to string	`NULL`
`fgetwc()`	Wide character read	`WEOF`¹
`fopen()`	Pointer to stream	`NULL`
`fopen_s()`	`0`	Nonzero
`fprintf()`	Number of characters (nonnegative)	Negative
`fprintf_s()`	Number of characters (nonnegative)	Negative
`fputc()`	Character written	`EOF`²
`fputs()`	Nonnegative	`EOF` (negative)
`fputwc()`	Wide character written	`WEOF`
`fputws()`	Nonnegative	`EOF` (negative)
`fread()`	Elements read	Elements read
`freopen()`	Pointer to stream	`NULL`
`freopen_s()`	`0`	Nonzero
`fscanf()`	Number of conversions (nonnegative)	`EOF` (negative)
`fscanf_s()`	Number of conversions (nonnegative)	`EOF` (negative)
`fseek()`	`0`	Nonzero
`fsetpos()`	`0`	Nonzero, `errno > 0`
`ftell()`	File position	`−1L`, `errno > 0`
`fwprintf()`	Number of wide characters (nonnegative)	Negative
`fwprintf_s()`	Number of wide characters (nonnegative)	Negative
`fwrite()`	Elements written	Elements written
`fwscanf()`	Number of conversions (nonnegative)	`EOF` (negative)
`fwscanf_s()`	Number of conversions (nonnegative)	`EOF` (negative)
`getc()`	Character read	`EOF`¹
`getchar()`	Character read	`EOF`¹
`getenv()`	Pointer to string	`NULL`
`getenv_s()`	Pointer to string	`NULL`
`gets_s()`	Pointer to string	`NULL`
`getwc()`	Wide character read	`WEOF`
`getwchar()`	Wide character read	`WEOF`
`gmtime()`	Pointer to broken-down time	`NULL`
`gmtime_s()`	Pointer to broken-down time	`NULL`
`localtime()`	Pointer to broken-down time	`NULL`
`localtime_s()`	Pointer to broken-down time	`NULL`
`malloc()`	Pointer to space	`NULL`
`mblen(), s != NULL`	Number of bytes	`−1`
`mbrlen(), s != NULL`	Number of bytes or status	`(size_t)(-1)`
`mbrtoc16()`	Number of bytes or status	`(size_t)(-1)`, `errno == EILSEQ`
`mbrtoc32()`	Number of bytes or status	`(size_t)(-1)`, `errno == EILSEQ`
`mbrtowc(), s != NULL`	Number of bytes or status	`(size_t)(-1)`, `errno == EILSEQ`
`mbsrtowcs()`	Number of non-null elements	`(size_t)(-1)`, `errno == EILSEQ`
`mbsrtowcs_s()`	`0`	Nonzero
`mbstowcs()`	Number of non-null elements	`(size_t)(-1)`
`mbstowcs_s()`	`0`	Nonzero
`mbtowc(), s != NULL`	Number of bytes	`−1`
`memchr()`	Pointer to located character	`NULL`
`mktime()`	Calendar time	`(time_t)(-1)`
`mtx_init()`	`thrd_success`	`thrd_error`
`mtx_lock()`	`thrd_success`	`thrd_error`
`mtx_timedlock()`	`thrd_success`	`thrd_timedout` or `thrd_error`
`mtx_trylock()`	`thrd_success`	`thrd_busy` or `thrd_error`
`mtx_unlock()`	`thrd_success`	`thrd_error`
`printf_s()`	Number of characters (nonnegative)	Negative
`putc()`	Character written	`EOF`²
`putwc()`	Wide character written	`WEOF`
`raise()`	`0`	Nonzero
`realloc()`	Pointer to space	`NULL`
`remove()`	`0`	Nonzero
`rename()`	`0`	Nonzero
`setlocale()`	Pointer to string	`NULL`
`setvbuf()`	`0`	Nonzero
`scanf()`	Number of conversions (nonnegative)	`EOF` (negative)
`scanf_s()`	Number of conversions (nonnegative)	`EOF` (negative)
`signal()`	Pointer to previous function	`SIG_ERR`, `errno > 0`
`snprintf()`	Number of characters that would be written (nonnegative)	Negative
`snprintf_s()`	Number of characters that would be written (nonnegative)	Negative
`sprintf()`	Number of non-null characters written	Negative
`sprintf_s()`	Number of non-null characters written	Negative
`sscanf()`	Number of conversions (nonnegative)	`EOF` (negative)
`sscanf_s()`	Number of conversions (nonnegative)	`EOF` (negative)
`strchr()`	Pointer to located character	`NULL`
`strerror_s()`	`0`	Nonzero
`strftime()`	Number of non-null characters	`0`
`strpbrk()`	Pointer to located character	`NULL`
`strrchr()`	Pointer to located character	`NULL`
`strstr()`	Pointer to located string	`NULL`
`strtod()`	Converted value	`0`, `errno == ERANGE`
`strtof()`	Converted value	`0`, `errno == ERANGE`
`strtoimax()`	Converted value	`INTMAX_MAX` or `INTMAX_MIN`, `errno == ERANGE`
`strtok()`	Pointer to first character of a token	`NULL`
`strtok_s()`	Pointer to first character of a token	`NULL`
`strtol()`	Converted value	`LONG_MAX` or `LONG_MIN`, `errno == ERANGE`
`strtold()`	Converted value	`0, errno == ERANGE`
`strtoll()`	Converted value	`LLONG_MAX` or `LLONG_MIN`, `errno == ERANGE`
`strtoumax()`	Converted value	`UINTMAX_MAX`, `errno == ERANGE`
`strtoul()`	Converted value	`ULONG_MAX`, `errno == ERANGE`
`strtoull()`	Converted value	`ULLONG_MAX`, `errno == ERANGE`
`strxfrm()`	Length of transformed string	`>= n`
`swprintf()`	Number of non-null wide characters	Negative
`swprintf_s()`	Number of non-null wide characters	Negative
`swscanf()`	Number of conversions (nonnegative)	`EOF` (negative)
`swscanf_s()`	Number of conversions (nonnegative)	`EOF` (negative)
`thrd_create()`	`thrd_success`	`thrd_nomem` or `thrd_error`
`thrd_detach()`	`thrd_success`	`thrd_error`
`thrd_join()`	`thrd_success`	`thrd_error`
`thrd_sleep()`	`0`	Negative
`time()`	Calendar time	`(time_t)(-1)`
`timespec_get()`	Base	`0`
`tmpfile()`	Pointer to stream	`NULL`
`tmpfile_s()`	`0`	Nonzero
`tmpnam()`	Non-null pointer	`NULL`
`tmpnam_s()`	`0`	Nonzero
`tss_create()`	`thrd_success`	`thrd_error`
`tss_get()`	Value of thread-specific storage	`0`
`tss_set()`	`thrd_success`	`thrd_error`
`ungetc()`	Character pushed back	`EOF` (see below)
`ungetwc()`	Character pushed back	`WEOF`
`vfprintf()`	Number of characters (nonnegative)	Negative
`vfprintf_s()`	Number of characters (nonnegative)	Negative
`vfscanf()`	Number of conversions (nonnegative)	`EOF` (negative)
`vfscanf_s()`	Number of conversions (nonnegative)	`EOF` (negative)
`vfwprintf()`	Number of wide characters (nonnegative)	Negative
`vfwprintf_s()`	Number of wide characters (nonnegative)	Negative
`vfwscanf()`	Number of conversions (nonnegative)	`EOF` (negative)
`vfwscanf_s()`	Number of conversions (nonnegative)	`EOF` (negative)
`vprintf_s()`	Number of characters (nonnegative)	Negative
`vscanf()`	Number of conversions (nonnegative)	`EOF` (negative)
`vscanf_s()`	Number of conversions (nonnegative)	`EOF` (negative)
`vsnprintf()`	Number of characters that would be written (nonnegative)	Negative
`vsnprintf_s()`	Number of characters that would be written (nonnegative)	Negative
`vsprintf()`	Number of non-null characters (nonnegative)	Negative
`vsprintf_s()`	Number of non-null characters (nonnegative)	Negative
`vsscanf()`	Number of conversions (nonnegative)	`EOF` (negative)
`vsscanf_s()`	Number of conversions (nonnegative)	`EOF` (negative)
`vswprintf()`	Number of non-null wide characters	Negative
`vswprintf_s()`	Number of non-null wide characters	Negative
`vswscanf()`	Number of conversions (nonnegative)	`EOF` (negative)
`vswscanf_s()`	Number of conversions (nonnegative)	`EOF` (negative)
`vwprintf_s()`	Number of wide characters (nonnegative)	Negative
`vwscanf()`	Number of conversions (nonnegative)	`EOF` (negative)
`vwscanf_s()`	Number of conversions (nonnegative)	`EOF` (negative)
`wcrtomb()`	Number of bytes stored	`(size_t)(-1)`
`wcschr()`	Pointer to located wide character	`NULL`
`wcsftime()`	Number of non-null wide characters	`0`
`wcspbrk()`	Pointer to located wide character	`NULL`
`wcsrchr()`	Pointer to located wide character	`NULL`
`wcsrtombs()`	Number of non-null bytes	`(size_t)(-1)`, `errno == EILSEQ`
`wcsrtombs_s()`	`0`	Nonzero
`wcsstr()`	Pointer to located wide string	`NULL`
`wcstod()`	Converted value	`0`, `errno == ERANGE`
`wcstof()`	Converted value	`0`, `errno == ERANGE`
`wcstoimax()`	Converted value	`INTMAX_MAX` or `INTMAX_MIN`, `errno == ERANGE`
`wcstok()`	Pointer to first wide character of a token	`NULL`
`wcstok_s()`	Pointer to first wide character of a token	`NULL`
`wcstol()`	Converted value	`LONG_MAX` or `LONG_MIN`, `errno == ERANGE`
`wcstold()`	Converted value	`0`, `errno == ERANGE`
`wcstoll()`	Converted value	`LLONG_MAX` or `LLONG_MIN`, `errno == ERANGE`
`wcstombs()`	Number of non-null bytes	`(size_t)(-1)`
`wcstombs_s()`	`0`	Nonzero
`wcstoumax()`	Converted value	`UINTMAX_MAX`, `errno == ERANGE`
`wcstoul()`	Converted value	`ULONG_MAX`, `errno == ERANGE`
`wcstoull()`	Converted value	`ULLONG_MAX`, `errno == ERANGE`
`wcsxfrm()`	Length of transformed wide string	`>= n`
`wctob()`	Converted character	`EOF`
`wctomb(), s != NULL`	Number of bytes stored	`−1`
`wctomb_s(), s != NULL`	Number of bytes stored	`−1`
`wctrans()`	Valid argument to `towctrans`	`0`
`wctype()`	Valid argument to `iswctype`	`0`
`wmemchr()`	Pointer to located wide character	`NULL`
`wprintf_s()`	Number of wide characters (nonnegative)	Negative
`wscanf()`	Number of conversions (nonnegative)	`EOF` (negative)
`wscanf_s()`	Number of conversions (nonnegative)	`EOF` (negative)

Note: According to FIO35-C . Use feof() and ferror() to detect end-of-file and file errors when sizeof(int) == sizeof(char), callers should verify end-of-file and file errors for the functions in this table as follows:

¹By calling ferror() and feof()²By calling ferror()

The ungetc() function does not set the error indicator even when it fails, so it is not possible to check for errors reliably unless it is known that the argument is not equal to EOF. The C Standard [ISO/IEC 9899:2011] states that "one character of pushback is guaranteed," so this should not be an issue if, at most, one character is ever pushed back before reading again. (See FIO13-C . Never push back anything other than one read character.)

Noncompliant Code Example (`setlocale()`)

In this noncompliant code example, the function utf8_to_wcs() attempts to convert a sequence of UTF-8 characters to wide characters. It first invokes setlocale() to set the global locale to the implementation-defined en_US.UTF-8 but does not check for failure. The setlocale() function will fail by returning a null pointer, for example, when the locale is not installed. The function may fail for other reasons as well, such as the lack of resources. Depending on the sequence of characters pointed to by utf8, the subsequent call to mbstowcs() may fail or result in the function storing an unexpected sequence of wide characters in the supplied buffer wcs.

#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;
}

Compliant Solution (`setlocale()`)

This compliant solution checks the value returned by setlocale() and avoids calling mbstowcs() if the function fails. The function also takes care to restore the locale to its initial setting before returning control to the caller.

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

Noncompliant Code Example (`calloc()`)

In this noncompliant code example, temp_num, tmp2, and num_of_records are derived from a tainted source. Consequently, an attacker can easily cause calloc() to fail by providing a large value for num_of_records.

#include <stdlib.h>
#include <string.h>
 
enum { SIG_DESC_SIZE = 32 };

typedef struct {
  char sig_desc[SIG_DESC_SIZE];
} signal_info;
 
void func(size_t num_of_records, size_t temp_num,
          const char *tmp2, size_t tmp2_size_bytes) {
  signal_info *start = (signal_info *)calloc(num_of_records,
                                          sizeof(signal_info));

  if (tmp2 == NULL) {
    /* Handle error */
  } else if (temp_num > num_of_records) {
    /* Handle error */
  } else if (tmp2_size_bytes < SIG_DESC_SIZE) {
    /* Handle error */
  }

  signal_info *point = start + temp_num - 1;
  memcpy(point->sig_desc, tmp2, SIG_DESC_SIZE);
  point->sig_desc[SIG_DESC_SIZE - 1] = '\0';
  /* ... */
  free(start);
}

When calloc() fails, it returns a null pointer that is assigned to start. If start is null, an attacker can provide a value for temp_num that, when scaled by sizeof(signal_info), references a writable address to which control is eventually transferred. The contents of the string referenced by tmp2 can then be used to overwrite the address, resulting in an arbitrary code execution vulnerability.

Compliant Solution (`calloc()`)

To correct this error, ensure the pointer returned by calloc() is not null:

#include <stdlib.h>
#include <string.h>

enum { SIG_DESC_SIZE = 32 };

typedef struct {
  char sig_desc[SIG_DESC_SIZE];
} signal_info;
 
void func(size_t num_of_records, size_t temp_num,
          const char *tmp2, size_t tmp2_size_bytes) {
  signal_info *start = (signal_info *)calloc(num_of_records,
                                           sizeof(signal_info));
  if (start == NULL) {
    /* Handle allocation error */
  } else if (tmp2 == NULL) {
    /* Handle error */
  } else if (temp_num > num_of_records) {
    /* Handle error */
  } else if (tmp2_size_bytes < SIG_DESC_SIZE) {
    /* Handle error */
  }

  signal_info *point = start + temp_num - 1; 
  memcpy(point->sig_desc, tmp2, SIG_DESC_SIZE);
  point->sig_desc[SIG_DESC_SIZE - 1] = '\0';
  /* ... */
  free(start);
}

Noncompliant Code Example (`realloc()`)

This noncompliant code example calls realloc() to resize the memory referred to by p. However, if realloc() fails, it returns a null pointer and the connection between the original block of memory and p is lost, resulting in a memory leak.

#include <stdlib.h>
 
void *p;
void func(size_t new_size) {
  if (new_size == 0) {
    /* Handle error */
  }
  p = realloc(p, new_size);
  if (p == NULL) {
   /* Handle error */
  }
}

This code example complies with MEM04-C . Do not perform zero-length allocations.

Compliant Solution (`realloc()`)

In this compliant solution, the result of realloc() is assigned to the temporary pointer q and validated before it is assigned to the original pointer p:

#include <stdlib.h>
 
void *p;
void func(size_t new_size) {
  void *q;

  if (new_size == 0) {
    /* Handle error */
  }
 
  q = realloc(p, new_size);
  if (q == NULL) {
   /* Handle error */
  } else {
    p = q;
  }
}

Noncompliant Code Example (`fseek()`)

In this noncompliant code example, the fseek() function is used to set the file position to a location offset in the file referred to by file prior to reading a sequence of bytes from the file. However, if an I/O error occurs during the seek operation, the subsequent read will fill the buffer with the wrong contents.

#include <stdio.h>
 
size_t read_at(FILE *file, long offset,
               void *buf, size_t nbytes) {
  fseek(file, offset, SEEK_SET);
  return fread(buf, 1, nbytes, file);
}

Compliant Solution (`fseek()`)

According to the C Standard, the fseek() function returns a nonzero value to indicate that an error occurred. This compliant solution tests for this condition before reading from a file to eliminate the chance of operating on the wrong portion of the file if fseek() fails:

#include <stdio.h>
 
size_t read_at(FILE *file, long offset,
               void *buf, size_t nbytes) {
  if (fseek(file, offset, SEEK_SET) != 0) {
    /* Indicate error to caller */
    return 0;
  }
  return fread(buf, 1, nbytes, file);
}

Noncompliant Code Example (`snprintf()`)

In this noncompliant code example, snprintf() is assumed to succeed. However, if the call fails (for example, because of insufficient memory, as described in GNU libc bug 441945), the subsequent call to log_message() has undefined behavior because the character buffer is uninitialized and need not be null-terminated.

#include <stdio.h>
 
extern void log_message(const char *);

void f(int i, int width, int prec) {
  char buf[40];
  snprintf(buf, sizeof(buf), "i = %*.*i", width, prec, i);
  log_message(buf);
  /* ... */
}

Compliant Solution (`snprintf()`)

This compliant solution does not assume that snprintf() will succeed regardless of its arguments. It tests the return value of snprintf() before subsequently using the formatted buffer. This compliant solution also treats the case where the static buffer is not large enough for snprintf() to append the terminating null character as an error.

#include <stdio.h>
#include <string.h>
 
extern void log_message(const char *);

void f(int i, int width, int prec) {
  char buf[40];
  int n;
  n = snprintf(buf, sizeof(buf), "i = %*.*i", width, prec, i);
  if (n < 0 || n >= sizeof(buf)) {
    /* Handle snprintf() error */
    strcpy(buf, "unknown error");
  }
  log_message(buf);
}

Compliant Solution (`snprintf(`null`)`)

If unknown, the length of the formatted string can be discovered by invoking snprintf() with a null buffer pointer to determine the size required for the output, then dynamically allocating a buffer of sufficient size, and finally calling snprintf() again to format the output into the dynamically allocated buffer. Even with this approach, the success of all calls still needs to be tested, and any errors must be appropriately handled. A possible optimization is to first attempt to format the string into a reasonably small buffer allocated on the stack and, only when the buffer turns out to be too small, dynamically allocate one of a sufficient size:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
extern void log_message(const char *); 
 
void f(int i, int width, int prec) {
  char buffer[20];
  char *buf = buffer;
  int n  = sizeof(buffer);
  const char fmt[] = "i = %*.*i";

  n = snprintf(buf, n, fmt, width, prec, i);
  if (n < 0) {
    /* Handle snprintf() error */
    strcpy(buffer, "unknown error");
    goto write_log;
  }

  if (n < sizeof(buffer)) {
    goto write_log;
  }

  buf = (char *)malloc(n + 1);
  if (NULL == buf) {
    /* Handle malloc() error */
    strcpy(buffer, "unknown error");
    goto write_log;
  }

  n = snprintf(buf, n, fmt, width, prec, i);
  if (n < 0) {
    /* Handle snprintf() error */
    strcpy(buffer, "unknown error");
  }

write_log:
  log_message(buf);

  if (buf != buffer) {
    free(buf);
  }
}

This solution uses the goto statement, as suggested in MEM12-C . Consider using a goto chain when leaving a function on error when using and releasing resources.

Exceptions

ERR33-C-EX1: It is acceptable to ignore the return value of a function that cannot fail, or a function whose return value is inconsequential, or when an error condition need not be diagnosed. The function's results should be explicitly cast to void to signify programmer intent. Return values from the functions in the following table do not need to be checked because their historical use has overwhelmingly omitted error checking and the consequences are not relevant to security.

Functions for which Return Values Need Not Be Checked

Function	Successful Return	Error Return
`putchar()`	Character written	`EOF`
`putwchar()`	Wide character written	`WEOF`
`puts()`	Nonnegative	`EOF` (negative)
`printf()`, `vprintf()`	Number of characters (nonnegative)	Negative
`wprintf()`, `vwprintf()`	Number of wide characters (nonnegative)	Negative
`kill_dependency()`	The input parameter	NA
`memcpy()`, `wmemcpy()`	The destination input parameter	NA
`memmove()`, `wmemmove()`	The destination input parameter	NA
`strcpy()`, `wcscpy()`	The destination input parameter	NA
`strncpy()`, `wcsncpy()`	The destination input parameter	NA
`strcat()`, `wcscat()`	The destination input parameter	NA
`strncat()`, `wcsncat()`	The destination input parameter	NA
`memset()`, `wmemset()`	The destination input parameter	NA

Risk Assessment

Failing to detect error conditions can lead to unpredictable results, including abnormal program termination and denial-of-service attacks or, in some situations, could even allow an attacker to run arbitrary code.

Rule	Severity	Likelihood	Remediation Cost	Priority	Level
ERR33-C	High	Likely	Medium	P18	L1

Automated Detection

Tool	Version	Checker	Description
Astrée	24.04	error-information-unused error-information-unused-computed	Partially checked
Axivion Bauhaus Suite	7.2.0	CertC-ERR33
CodeSonar	8.1p0	LANG.FUNCS.IRV	Ignored return value
Compass/ROSE			Can detect violations of this recommendation when checking for violations of EXP12-C. Do not ignore values returned by functions and EXP34-C . Do not dereference null pointers
Coverity	2017.07	MISRA C 2012 Rule 22.8 MISRA C 2012 Rule 22.9 MISRA C 2012 Rule 22.10	Implemented
LDRA tool suite	9.7.1	80 D	Partially implemented
Parasoft C/C++test	2023.1	CERT_C-ERR33-a CERT_C-ERR33-b CERT_C-ERR33-c CERT_C-ERR33-d	The value returned by a function having non-void return type shall be used The value returned by a function having non-void return type shall be used Avoid null pointer dereferencing Always check the returned value of non-void function
Parasoft Insure++			Runtime analysis
Polyspace Bug Finder	R2024a	Errno not checked Return value of a sensitive function not checked Unprotected dynamic memory allocation MISRA C:2012 Rule 17.7 MISRA C:2012 Rule 22.9	errno is not checked for error conditions following function call Sensitive functions called without checking for unexpected return values and errors Pointer returned from dynamic allocation not checked for `NULL` value The value returned by a function having non-void return type shall be used The value of `errno` shall be tested against zero after calling an `errno`-setting function
PRQA QA-C	Unable to render {include} The included page could not be found.	3200	Partially implemented
PRQA QA-C++	4.4	2820, 2821, 2822, 2823, 2824, 2930, 2931, 2932, 2933, 2934, 3802, 3803, 3804
RuleChecker	24.04	error-information-unused	Partially checked

Related Vulnerabilities

The vulnerability in Adobe Flash [VU#159523] arises because Flash neglects to check the return value from calloc(). Even when calloc() returns a null pointer, Flash writes to an offset from the return value. Dereferencing a null pointer usually results in a program crash, but dereferencing an offset from a null pointer allows an exploit to succeed without crashing the program.

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

Related Guidelines

Key here (explains table format and definitions)

Taxonomy	Taxonomy item	Relationship
CERT C Secure Coding Standard	ERR00-C. Adopt and implement a consistent and comprehensive error-handling policy	Prior to 2018-01-12: CERT: Unspecified Relationship
CERT C Secure Coding Standard	EXP34-C . Do not dereference null pointers	Prior to 2018-01-12: CERT: Unspecified Relationship
CERT C Secure Coding Standard	FIO13-C . Never push back anything other than one read character	Prior to 2018-01-12: CERT: Unspecified Relationship
CERT C Secure Coding Standard	MEM04-C . Do not perform zero-length allocations	Prior to 2018-01-12: CERT: Unspecified Relationship
CERT C Secure Coding Standard	MEM12-C . Consider using a goto chain when leaving a function on error when using and releasing resources	Prior to 2018-01-12: CERT: Unspecified Relationship
CERT C	ERR10-CPP. Check for error conditions	Prior to 2018-01-12: CERT: Unspecified Relationship
CERT C	FIO04-CPP. Detect and handle input and output errors	Prior to 2018-01-12: CERT: Unspecified Relationship
ISO/IEC TS 17961:2013	Failing to detect and handle standard library errors [liberr]	Prior to 2018-01-12: CERT: Unspecified Relationship
CWE 2.11	CWE-252, Unchecked Return Value	2017-07-06: CERT: Partial overlap
CWE 2.11	CWE-253, Incorrect Check of Function Return Value	2017-07-06: CERT: Partial overlap
CWE 2.11	CWE-391, Unchecked Error Condition	2017-07-06: CERT: Rule subset of CWE

CERT-CWE Mapping Notes

Key here for mapping notes

CWE-252/CWE-253/CWE-391 and ERR33-C/POS34-C

Independent( ERR33-C, POS54-C, FLP32-C, ERR34-C) Intersection( CWE-252, CWE-253) = Ø CWE-391 = Union( CWE-252, CWE-253) CWE-391 = Union( ERR33-C, POS34-C, list) where list =

Ignoring return values of functions outside the C or POSIX standard libraries

Bibliography

[DHS 2006]	Handle All Errors Safely
[Henricson 1997]	Recommendation 12.1, "Check for All Errors Reported from Functions"
[ISO/IEC 9899:2011]	Subclause 7.21.7.10, "The `ungetc` Function"
[VU#159523]

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Noncompliant Code Example (`setlocale()`)

Compliant Solution (`setlocale()`)

Noncompliant Code Example (`calloc()`)

Compliant Solution (`calloc()`)

Noncompliant Code Example (`realloc()`)

Compliant Solution (`realloc()`)

Noncompliant Code Example (`fseek()`)

Compliant Solution (`fseek()`)

Noncompliant Code Example (`snprintf()`)

Compliant Solution (`snprintf()`)

Compliant Solution (`snprintf(`null`)`)

Exceptions

Risk Assessment

Automated Detection

Related Vulnerabilities

Related Guidelines

CERT-CWE Mapping Notes

CWE-252/CWE-253/CWE-391 and ERR33-C/POS34-C

Bibliography

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ERR33-C. Detect and handle standard library errors

Noncompliant Code Example (setlocale())

Compliant Solution (setlocale())

Noncompliant Code Example (calloc())

Compliant Solution (calloc())

Noncompliant Code Example (realloc())

Compliant Solution (realloc())

Noncompliant Code Example (fseek())

Compliant Solution (fseek())

Noncompliant Code Example (snprintf())

Compliant Solution (snprintf())

Compliant Solution (snprintf(null))

Exceptions

Risk Assessment

Automated Detection

Related Vulnerabilities

Related Guidelines

CERT-CWE Mapping Notes

CWE-252/CWE-253/CWE-391 and ERR33-C/POS34-C

Bibliography

Noncompliant Code Example (`setlocale()`)

Compliant Solution (`setlocale()`)

Noncompliant Code Example (`calloc()`)

Compliant Solution (`calloc()`)

Noncompliant Code Example (`realloc()`)

Compliant Solution (`realloc()`)

Noncompliant Code Example (`fseek()`)

Compliant Solution (`fseek()`)

Noncompliant Code Example (`snprintf()`)

Compliant Solution (`snprintf()`)

Compliant Solution (`snprintf(`null`)`)