libdill: Structured Concurrency for C

NAME

go - launches a coroutine

SYNOPSIS

#include <libdill.h>

int go(
    expression);

DESCRIPTION

This construct launches a coroutine. The coroutine gets a 1MB stack. The stack is guarded by a non-writeable memory page. Therefore, stack overflow will result in a SEGFAULT rather than overwriting memory that doesn't belong to it.

expression: Expression to evaluate as a coroutine.

The coroutine is executed concurrently, and its lifetime may exceed the lifetime of the caller coroutine. The return value of the coroutine, if any, is discarded and cannot be retrieved by the caller.

Any function to be invoked as a coroutine must be declared with the coroutine specifier.

Use hclose to cancel the coroutine. When the coroutine is canceled all the blocking calls within the coroutine will start failing with ECANCELED error.

WARNING: Coroutines will most likely work even without the coroutine specifier. However, they may fail in random non-deterministic ways, depending on the code in question and the particular combination of compiler and optimization level. Additionally, arguments to a coroutine must not be function calls. If they are, the program may fail non-deterministically. If you need to pass a result of a computation to a coroutine, do the computation first, and then pass the result as an argument. Instead of:

go(bar(foo(a)));

Do this:

int a = foo();
go(bar(a));

RETURN VALUE

In case of success the function returns handle of a bundle containing the new coroutine. In case of error it returns -1 and sets errno to one of the values below.

For details on coroutine bundles see bundle function.

ERRORS

ECANCELED: Current coroutine was canceled.
EMFILE: The maximum number of file descriptors in the process are already open.
ENFILE: The maximum number of file descriptors in the system are already open.
ENOMEM: Not enough memory.

EXAMPLE

coroutine void add(int a, int b) {
    printf("%d+%d=%d\n", a, b, a + b);
}

...

int h = go(add(1, 2));