HP C/aC++ for PA-RISC Software Attribute format, Attribute visibility, Attribute warnunusedresult

Similar to the NO_RETURN pragma, this attribute asserts to the optimizer that this function never returns to the call site. This allows the optimizer to delete any code after the function call. A C++ function marked with this attribute may still throw an exception unless it has an empty throw list.

Example:

void foo(int i) __attribute__ ((noreturn));

attribute format

__attribute__ ((format(type, arg_format_string, arg_check_start)))

The format attribute specifies that a function takes printf, scanf, strftime or strfmon style arguments which should be type-checked against a format string. In the example above, the format string is the second argument of the function foo and the arguments to check start with the third argument.

Example:

int foo(int i, const char *my_format, ...) __attribute__((format(printf, 2, 3)));

attribute visibility

__attribute__ ((visibility("default""protected""hidden")))

The visibility attributes "default", "protected", and "hidden", are equivalent to the options -Bdefault, -Bprotected, and -Bhidden, and the pragmas DEFAULT_BINDING, EXTERN, and HIDDEN, respectively.

Example:

void foo(int i) __attribute__ ((visibility("hidden"));

attribute warn_unused_result

__attribute__ ((warn_unused_result))

If a caller of a function with this attribute does not use its return value, the compiler emits a warning. This is useful for functions where not checking the result can be a security problem or always a program bug, as with realloc. The following example results in a warning on line 5:

int fn () __attribute__ ((warn_unused_result)); int test()

{

if (fn () < 0) return -1; fn ();

return 0;

}

118 Pragma Directives and Attributes