returned if there is an error, such as if a precondition is not met. The
default is 0, casted to the type of the method. If you need to return
something else then you can specify an "onerror" keyword after the
prototype and after that a number, a token (an identifier) or a bit of C
code enclosed in braces {}. The braces will not be printed into the
output, they just delimit the string. For example
returned if there is an error, such as if a precondition is not met. The
default is 0, casted to the type of the method. If you need to return
something else then you can specify an "onerror" keyword after the
prototype and after that a number, a token (an identifier) or a bit of C
code enclosed in braces {}. The braces will not be printed into the
output, they just delimit the string. For example