__UNCONST(3)

__UNCONST(3) | Library Functions Manual | __UNCONST(3)

# NAME

__UNCONST — compile time cast-away macro

# SYNOPSIS

#include <sys/cdefs.h>
void
__UNCONST(x);
void
__UNVOLATILE(x);

# DESCRIPTION

The __UNCONST() macro can be used to omit warnings produced by certain compilers when operating with pointers declared with the const type qualifier in a context without such qualifier. Examples include passing a pointer declared with the const qualifier to a function without such qualifier, and variable assignment from a const pointer to a non-const pointer. In the same vein, the __UNVOLATILE() macro can be used to exclude warnings related to the volatile type qualifier.

# IMPLEMENTATION NOTES

These macros are implemented by explicitly using unsigned long instead of intptr_t, a signed type guaranteed to hold a pointer.

# SEE ALSO

cc(1), cdefs(3)

# CAVEATS

As both macros may hide valid errors, their usage is not recommended unless there is a well-thought reason for a cast. A typical use case for __UNCONST() involve an API that does not follow the so-called ``const correctness'' even if it would be appropriate. Valid use cases of __UNVOLATILE() include passing a volatile pointer to memset(3).
Use of this macro is non-portable; this is part of the implementation namespace and should only be used in NetBSD code.

October 17, 2013 | NetBSD 8.0