Rule 7.0.2: Unclear/questionable rationale

[cgpzs]

Hi,

Rule 7.0.2 bans any type of conversion to bool (implicit or explicit) anywhere in the code (with some exceptions). The rationale says:

"However, this interpretation may not be appropriate for APIs, such as POSIX, that do not use Boolean return values."

This sounds strange, why should modern C++17 code (that may not use C-style POSIX functions at all) be limited by this?

Could you show an example code that highlights how this is a problem and leads to unexpected behavior? For example, how is this code unsafe/can lead to unexpected results?

Code:

bool b1 = static_cast< bool >( 4 );  // Non-compliant

Conversion from fundamental types to bool is well-defined behavior as per [conv.bool]:

"A prvalue of arithmetic, unscoped enumeration, pointer, or pointer to member type can be converted to a prvalue of type bool. A zero value, null pointer value, or null member pointer value is converted to false; any other value is converted to true."

Thanks!

[misra cpp]

The issue is with functions like strcmp, where an implicit conversion to bool may not give the answer expected (0 being equality)

Also in a case like if (a = b) .... (though this is also non-compliant with another rule)