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However, note that both calling functions and accessing volatile-qualified objects can still be optimized out (while maintaining strict conformance to the standard), so this compliant solution still might not work in some cases.  The memset_s() function introduced in C11 is the preferred solution (see the following solution for more information).  If memset_s() function is not yet available on your implementation, this compliant solution is the best alternative, and can be discarded once supported by your implementation.

Compliant Solution (C11)

The C Standard includes a memset_s function. Subclause K.3.7.4.1, paragraph 4 [ISO/IEC 9899:2011], states:

Unlike memset, any call to the memset_s function shall be evaluated strictly according to the rules of the abstract machine as described in (5.1.2.3). That is, any call to the memset_s function shall assume that the memory indicated by s and n may be accessible in the future and thus must contain the values indicated by c.

void getPassword(void) {
  char pwd[64];

  if (retrievePassword(pwd, sizeof(pwd))) {
     /* Checking of password, secure operations, etc. */
  }
  memset_s(pwd, 0, sizeof(pwd));
}

Noncompliant Code Example

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Related Vulnerabilities

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

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Related Guidelines

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