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This non-compliant code example declares the variable p as a pointer to a constant char with file scope. The value of str is assigned to p within the dont_do_this() function. However, str has automatic storage duration, so the lifetime of str ends when the dont_do_this() function exits.

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As a result of this undefined behavior, it is likely that p will refer to the string literal "Surprise, surprise" after the call to the innocuous() function.

Compliant Solution (p with

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Block Scope)

In this compliant solution, p is declared with the same scope as str, preventing p from taking on an indeterminate value outside of this_is_OK().

void this_is_OK() {
    const char str[] = "Everything OK";
    const char *p = str;
    /* ... */
}
/* pointer p is now inaccessible outside the scope of string str */

Compliant Solution (p with

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File Scope)

If it is necessary for p to be defined with file scope, it can be set to NULL before str is destroyed. This prevents p from taking on an indeterminate value, although any references to p must check for NULL.

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Some compilers generate a warning when a local stack variable is returned from a function. Compile your code at high warning levels and resolve any warnings (see MSC00-A. Compile cleanly at high warning levels).

Compliant Solution (Return Values)

Correcting this example depends on the intent of the programmer. If the intent is to modify the value of array and have that modification persist outside of the scope of init_array(), then the desired behavior can be achieved by declaring array elsewhere and passing it as an argument to init_array().

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Coverity Prevent. The RETURN_LOCAL checker finds many instances where a function will return a pointer to a local stack variable. Coverity Prevent cannot discover all violations of this rule, so further verification is necessary.

References

\[[Coverity 07|AA. C References#Coverity 07]\]
\[[ISO/IEC 9899-1999|AA. C References#ISO/IEC 9899-1999]\] Section 6.2.4, "Storage durations of objects," and Section 7.20.3, "Memory management functions"
\[[Coverity 07|AA. C References#Coverity 07]\]

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DCL12-A. Create and use abstract data types      02. Declarations and Initialization (DCL))       DCL32-C. Guarantee identifiers are unique