This is a draft version of a MISRA C++ 202x rule proposed for public review.
MISRA Rule 6.7.1
Category: Required
Analysis Type: Decidable,Single Translation Unit
Amplification
This rule does not apply to variables declared constexpr or const.
Rationale
The use of mutable variables with static storage duration, even when they do not have linkage, potentially results in hidden temporal coupling.
This can lead to data races (and thus undefined behaviour). Additionally, functions with persistent state are usually more difficult to
understand and test.
Note: the lifetime of local variables with static storage duration ends at program termination in the reverse order of their
creation. Suitable care should be taken to ensure that the code executed during destruction does not access a previously destroyed variable.
Example
int32_t bar();
int32_t ga = 0; // Compliant - but violates "See also"
int32_t foo()
{
int32_t a = 0; // Compliant
static int32_t b = 0; // Non-compliant
static constexpr int32_t c = 0; // Compliant
static const int32_t d = bar(); // Compliant
}
class Application
{
static Application & theApp()
{
static Application app; // Non-compliant
return app;
}
};
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