__BUILTIN_TYPES_COMPATIBLE_P(3) | Library Functions Manual | __BUILTIN_TYPES_COMPATIBLE_P(3)

# 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.

December 21, 2010 | NetBSD 9.0