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Using anonymous pipes for jobserver support has some advantages: for example there is nothing on disk that needs to be cleaned up. However it has many obscure problems, related to the fact that in order for it to work we need to ensure these resources are properly passed through to child processes that want to use the jobserver. At the same time we don't want to pass the pipe to process which DON'T know about the jobserver. Other processes can open file descriptors which we then think are our jobserver, but aren't. And, we open the pipe file descriptors in blocking mode which doesn't work for all users. See issues such as SV 57178, SV 57242, and SV 62397 To avoid these issues, use named pipes (on systems where they are available) instead of anonoymous pipes. This simplifies many things: we never need to pass open file descriptors to our children; they can open the jobserver named pipe. We don't need to worry about recursive vs. non-recursive children. Users don't have to "pass through" the resources if they are invoking sub-makes. Each child can open its own file descriptor and set blocking as needed. The downside is the named pipe exists on disk and so must be cleaned up when the "top-level" make instance exits. In order to allow make to continue to be used in build systems where older versions of GNU make, or other tools that want to use the jobserver, but don't understand named pipes, introduce a new option --jobserver-style that allows the user to choose anonymous pipes. * NEWS: Announce the change and the --jobserver-style option. * doc/make.1: Add --jobserver-style documentation. * doc/make.texi (Special Variables): Add missing items to .FEATURES. (Options Summary): Add --jobserver-style. (POSIX Jobserver): Named pipes, changes to --jobserver-auth, and the --jobserver-style option. (Windows Jobserver): Document --jobserver-style for Windows. * configure.ac: Check for mkfifo. * src/config.h-vms.template: Undefined HAVE_MKFIFO. * src/config.h.W32.template: Ditto. * src/main.c: Add jobserver-style as a new command line option. (main): Add jobserver-fifo to .FEATURES if supported. Pass the style option to jobserver_setup(). * src/os.h (jobserver_setup): Accept a style string option. * src/posixos.c (enum js_type): Enumeration of the jobserver style. (js_type): Which style we are currently using. (fifo_name): The path to the named pipe (if in use). (jobserver_setup): If no style is given, or "fifo" is given, set up a named pipe: get a temporary file and use mkfifo() on it, then open it for reading and writing. If something fails fall back to anonymous pipes. (jobserver_parse_auth): Parse jobserver-auth to determine the style. If we are using a named pipe, open it. If we're using anonymous pipes ensure they're valid as before. (jobserver_get_invalid_auth): Don't invalidate the jobserver when using named pipes. (jobserver_clear): Clean up memory used for named pipes. (jobserver_acquire_all): Unlink the named pipe when done. * src/w32/w32os.c (jobserver_setup): Check the style argument. * tests/scripts/features/jobserver: Use --jobserver-style to test the anonymous pipe behavior, and also test named pipe/semaphore behavior. Check invalid jobserver-style options. * tests/scripts/functions/shell: Use --jobserver-style to test the anonymous pipe behavior, and also test named pipe/semaphore behavior. |
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