While rule DCL50-CPP. Do not define a C-style variadic function forbids creation of such functions, they may still be defined when that function has external, C language linkage. Under these circumstances, care must be taken when invoking the va_start() macro. The C-standard library macro va_start() imposes several semantic restrictions on the type of the value of its second parameter. The C Standard, subclause 7.16.1.4, paragraph 4 [ISO/IEC 9899:2011], states the following:
The parameter parmN is the identifier of the rightmost parameter in the variable parameter list in the function definition (the one just before the
...). If the parameter parmN is declared with theregisterstorage class, with a function or array type, or with a type that is not compatible with the type that results after application of the default argument promotions, the behavior is undefined.
...
Passing an object of an unsupported type as the second argument to va_start() can result in undefined behavior that might be exploited to cause data integrity violations.
Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
EXP58-CPP | Medium | Unlikely | Medium | P4 |
L3 |
Automated Detection
Tool | Version | Checker | Description | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Clang |
| -Wvarargs | Does not catch the violation in the third noncompliant code example (it is conditionally supported by Clang) | ||||||
| CodeSonar |
| BADMACRO.STDARG_H | Use of <stdarg.h> Feature | ||||||
| Helix QAC |
| C++3852, C++3853 | |||||||
| Klocwork |
| CERT.VA_START.TYPE | |||||||
| Parasoft C/C++test |
| CERT_CPP-EXP58-a | Use macros for variable arguments correctly | ||||||
| Polyspace Bug Finder |
| CERT C++: EXP58-CPP | Checks for incorrect data types for second argument of va_start (rule fully covered) |
Related Vulnerabilities
Search for vulnerabilities resulting from the violation of this rule on the CERT website.
Related Guidelines
Bibliography
| [ISO/IEC 9899:2011] | Subclause 7.16.1.4, "The va_start Macro" |
| [ISO/IEC 14882-2014] | Subclause 18.10, "Other Runtime Support" |
...
...