The warn.h header

#include "/package/prog/prjlibs/include/warn.h"
{
  WARN_CHK(1>=1u);
  WARN_TYPE(char*, "foo");
  WARN_PTYPE(char**, "foo");
  WARN_CAST(char*, "foo");
  WARN_ARR(char, "foo");
  WARN_IF(1==0);
  if (NOWARN_SIGNED(uid_t)) { ... }
  if (NOWARN_UNSIGNED(uid_t)) { ... }
  if (NOWARN_NEGATIVE(uid_t, uid)) { ... }
}

The warn.h C header file provides macros to provoke or inhibit compiler warnings.

• WARN_CHK(expr) is a void expression which avoids evaluating the given expression at run time, but still allows it to be visible to the compiler to provoke warnings.
• WARN_TYPE(type, expr) is a void expression triggering a warning if the given expression is not assignment-compatible with the given type. It is mostly useful in the definitions of other macros, when you want to perform type checking as functions do. The given expression is not evaluated at run time. The type must be specified in a form that can have "*" appended to it to form the associated pointer type - in particular, pointer-to-function and pointer-to-array types must be specified through typedefs.
• WARN_PTYPE(ptype, expr) is a void expression triggering a warning if the given expression is not assignment-compatible with the dereferenced form of the given type. It is useful for pointer-to-function and pointer-to-array types, where WARN_TYPE cannot be used.
• WARN_CAST(type, expr) evaluates to the given expression, cast to the given type, but triggering a warning if the expression is not assignment compatible with that type. The type specification has the same restrictions as with WARN_TYPE.
• WARN_ARR(type, expr) is a void expression triggering a warning if the given expression is not an array whose base type is the given type. It is mostly useful in the definitions of other macros, when you want to perform type checking as functions do. The given expression is not evaluated at run time.
• WARN_IF(expr) is a void expression triggering a warning if the given expression evaluates to nonzero. The expression should be an integer constant expression; it is not evaluated at run time.
• NOWARN_SIGNED(type) returns nonzero iff the given integer type is signed, without triggering a warning.
• NOWARN_UNSIGNED(type) returns nonzero iff the given integer type is unsigned, without triggering a warning.
• NOWARN_NEGATIVE(type, expr) returns nonzero iff the given expression, when cast to the given type, yields a negative value, without triggering a warning. The expression may be evaluated more than once.