[Issue 15768] std.stdio.trustedStdout accesses __gshared data without synchronization.

https://issues.dlang.org/show_bug.cgi?id=15768 Ivan Kazmenko <gassa@mail.ru> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |gassa@mail.ru --

https://issues.dlang.org/show_bug.cgi?id=15768 --- Comment #1 from github-bugzilla@puremagic.com --- Commits pushed to stable at https://github.com/dlang/phobos https://github.com/dlang/phobos/commit/92eed4f45ed01a5d1f975fb23859ea63473e6f5e Warn about Issue 15768 https://github.com/dlang/phobos/commit/02d1aedf6d3d001989ee342eae6d9fc6db61d399 Merge pull request #4401 from JackStouffer/patch-9 Warn about Issue 15768 --

https://issues.dlang.org/show_bug.cgi?id=15768 Jack Stouffer <jack@jackstouffer.com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |jack@jackstouffer.com --- Comment #2 from Jack Stouffer <jack@jackstouffer.com> --- In order for stdout, stdin, and stderr to be shared(File), I think File needs huge rewrites that will end up being backwards incompatible. Either that, or you need to write a second implementation of File that supports shared and has a lot less functionality. --

https://issues.dlang.org/show_bug.cgi?id=15768 --- Comment #3 from Sobirari Muhomori <dfj1esp02@sneakemail.com> --- I'd say follow TLS-cached singleton pattern, FILE* can be shared, but the reference counter must be separate. --

https://issues.dlang.org/show_bug.cgi?id=15768 Sobirari Muhomori <dfj1esp02@sneakemail.com> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |safe --

https://issues.dlang.org/show_bug.cgi?id=15768 Walter Bright <bugzilla@digitalmars.com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |thecybershadow@gmail.com --- Comment #4 from Walter Bright <bugzilla@digitalmars.com> --- *** Issue 13443 has been marked as a duplicate of this issue. *** --

https://issues.dlang.org/show_bug.cgi?id=15768 --- Comment #5 from github-bugzilla@puremagic.com --- Commits pushed to master at https://github.com/dlang/phobos https://github.com/dlang/phobos/commit/92eed4f45ed01a5d1f975fb23859ea63473e6f5e Warn about Issue 15768 https://github.com/dlang/phobos/commit/02d1aedf6d3d001989ee342eae6d9fc6db61d399 Merge pull request #4401 from JackStouffer/patch-9 --

https://issues.dlang.org/show_bug.cgi?id=15768 --- Comment #6 from Sobirari Muhomori <dfj1esp02@sneakemail.com> --- (In reply to Jack Stouffer from comment #2) > In order for stdout, stdin, and stderr to be shared(File) 1. shared(File) stdio will break code that consumes it as unshared 2. always doing interlocked counting for shared(File) is still slow, consider this optimization: https://dpaste.dzfl.pl/d8dab5b7aa1f --

July 28, 2016

[Issue 15768] std.stdio.trustedStdout accesses __gshared data without synchronization.

Posted by Jack Stouffer

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Jack Stouffer

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https://issues.dlang.org/show_bug.cgi?id=15768

--- Comment #7 from Jack Stouffer <jack@jackstouffer.com> ---
(In reply to Sobirari Muhomori from comment #6)
> (In reply to Jack Stouffer from comment #2)
> > In order for stdout, stdin, and stderr to be shared(File)
> 
> 1. shared(File) stdio will break code that consumes it as unshared

Yup, and I don't see a way around that. Apparently when std.stdio was designed, shared still had bugs, so it wasn't used and __gshared was chosen instead. That was a huge mistake that we are now paying for. shared is the right choice here; this is specifically what shared was designed for.

OT: IMO anytime __gshared shows up in Phobos outside of C bindings, it's a bug. I don't care if it's using locks, or the code is slightly slower, we need to dog food shared if shared going to get any good.

> 2. always doing interlocked counting for shared(File) is still slow, consider this optimization: https://dpaste.dzfl.pl/d8dab5b7aa1f

You can further optimize with a new implementation by removing the ref count from a non shared File instance.

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