Bug 7446 – [TDPL] Trivial asynchronous file copy example crashes with OwnerTerminated

import std.concurrency, std.stdio; void main() { enum bufferSize = 1024 * 100; auto tid = spawn(&fileWriter); // Read loop foreach (ubyte[] buffer; stdin.byChunk(bufferSize)) { send(tid, buffer.idup); } } void fileWriter() { // Write loop for (;;) { auto buffer = receiveOnly!(immutable(ubyte)[])(); stdout.rawWrite(buffer); } } TDPL says: "The writer thread exits with the OwnerTerminated exception, which is recognized by the runtime system, which simply ignores it." This program will cat stdin to stdout as expected, however on exit it will apparently crash with an OwnerTerminated exception. I should point out another oddity: the exception information (class, message, stack trace) are printed to STDOUT, not STDERR. When using this example program to copy a file using pipes, the exception is appended to the destination file.

This is a phobos bug, druntime can't know anything about phobos exception types. If this is intened behavior the OwnerTerminated exception should be catched in spawn's exec function (https://github.com/D-Programming-Language/phobos/blob/a0c7d834434222018c0f01ee72bc51842513fa23/std/concurrency.d#L487).

I can't find the original documentation about runtime anymore, but IMHO the receive-functions should mention the exception OwnerTerminated in its documentation. I'll file a PR.

@berni44 created dlang/phobos pull request #7333 "Fix Issue 7446 - [TDPL] Trivial asynchronous file copy example crashes" fixing this issue: - Fix Issue 7446 - [TDPL] Trivial asynchronous file copy example crashes with OwnerTerminated https://github.com/dlang/phobos/pull/7333

A trivial workaround of course is to do this: void fileWriter() { // Write loop for (;;) { try { auto buffer = receiveOnly!(immutable(ubyte)[])(); stdout.rawWrite(buffer); } catch(OwnerTerminated _) { return; } } }

dlang/phobos pull request #7333 "Fix Issue 7446 - [TDPL] Trivial asynchronous file copy example crashes" was merged into master: - 9340d7a6b170dc92a47ef8c9905b50a31430509d by Bernhard Seckinger: Fix Issue 7446 - [TDPL] Trivial asynchronous file copy example crashes with OwnerTerminated https://github.com/dlang/phobos/pull/7333