[ruby-core:61374] [ruby-trunk - Bug #9600] sysconf(_SC_GETGR_R_SIZE_MAX) is just a hint for getgrnam_r()

Issue #9600 has been updated by Daniel Berger.


I don't think there's a way to get it. You'll have to rescue and retry with a realloc'ed buffer.

One bit of trickiness is that different platforms seem to set errno to different values on different platforms. In my own sys-admin gem, I caught Errno::ERANGE on Linux and Solaris, while on Darwin it was Errno::ENOENT, and on FreeBSD it was Errno::ENOTTY.

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Bug #9600: sysconf(_SC_GETGR_R_SIZE_MAX) is just a hint for getgrnam_r()
https://bugs.ruby-lang.org/issues/9600#change-45685

* Author: Rei Odaira
* Status: Open
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
* ruby -v: ruby 2.2.0dev (2014-03-05) [powerpc64-linux]
* Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN, 2.1: UNKNOWN
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When there is a group that has a lot of members, TestProcess#test_execopts_gid fails.  Following is a more simple example:

    $ ruby -e 'system("true", gid: "largegroup")'
    -e:1:in `system': Numerical result out of range - getgrnam_r (Errno::ERANGE)
    from -e:1:in `<main>'

This wrong exception happens because obj2gid() in process.c calls getgrnam_r() with a buffer that was allocated based on the size returned by sysconf(_SC_GETGR_R_SIZE_MAX). In Linux, sysconf(_SC_GETGR_R_SIZE_MAX) returns 1024, but actually this value is just a hint, so obj2gid() should gradually extend the buffer until getgrnam_r() no longer throws ERANGE.

The same issue was reported in the following page:
http://tomlee.co/2012/10/problems-with-large-linux-unix-groups-and-getgrgid_r-getgrnam_r/



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