This diagnostic rule is based on the software development guidelines developed by MISRA (Motor Industry Software Reliability Association).
As defined by the C++ standard, macro names and identifiers that contain the '__' sequence anywhere or begin with '_[A-Z]' are reserved for use in the language and standard library implementation. The same rule applies to the C language as well, except that the '__' sequence should be at the beginning of a reserved identifier.
Declaring such identifiers outside the standard library may cause problems. For example, this code:
#define _BUILTIN_abs(x) (x < 0 ? -x : x)
#include <cmath>
int foo(int x, int y, bool c)
{
return abs(c ? x : y)
}may change the behavior of the 'abs' function if this function is implemented through the use of the compiler's built-in (intrinsic) function as follows:
#define abs(x) (_BUILTIN_abs(x))This diagnostic is classified as:
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