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The C Standard, Section subclause 6.7.3, paragraph 6 [ISO/IEC 9899:2011], states:

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The following well-formed but noncompliant code example borrowed from Section subclause 6.5.16.1 of the C Standard allows a constant value to be modified:

char const **cpp;
char *cp;
char const c = 'A';

cpp = &cp; /* constraintConstraint violation */
*cpp = &c; /* validValid */
*cp = 'B'; /* validValid */

The first assignment is unsafe because it would allow the valid code that follows to attempt to change the value of the const object c.

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Similarly to the previous example, the following well-formed but noncompliant code example modifies a constant object after casting away its constness constness. Compiling the program on a Linux/x64 system does not produce any diagnostics even at high warning levels, but the generated executable program fails at runtime with SIGESGV.

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If cpp, cp, and c are declared as automatic (stack) variables, this example compiles without warning on all versions of Microsoft Visual Studio when compiled in C mode (/TC). In both cases, the resulting program changes the value of c. Version GCC 3.2.2 of the GCC compiler generates a warning but compiles. The resulting program changes the value of c.

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

Bibliography

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