NAME

__builtin_types_compatible_p — GNU extension to check equivalent types

SYNOPSIS

int
__builtin_types_compatible_p(type_a, type_b);

DESCRIPTION

The __builtin_types_compatible_p() is a GNU extension for determining whether two types are equivalent. If type_a is equivalent to type_b, a value 1 is returned. Otherwise __builtin_types_compatible_p() returns 0.

The following remarks should be taken into account.

1. The architecture-specific size of the two types does not have an impact on the result. For example, sizeof(char *) and sizeof(int) result the same value on i386, but the types naturally are not equivalent.
2. Type qualifiers are ignored. The function returns the same value for long and const long.
3. The amount of pointer indirection affects the result. For example, double * is not equivalent to double **.
4. Two types defined with typedef are equivalent if and only if their underlying types are equivalent.
5. The enum type is a special case in that two enum types are not considered equivalent.

EXAMPLES

The following example combines __builtin_types_compatible_p() and the typeof(3) construct:

#define __COMPARE_TYPES(v, t)      \
         __builtin_types_compatible_p(__typeof__(v), t)

...

if (__COMPARE_TYPES(p, double) != 0)
	err(EX_DATAERR, "invalid type");

SEE ALSO

gcc(1), __builtin_constant_p(3), typeof(3)

CAVEATS

This is a non-standard, compiler-specific extension.