[ruby-core:61330] [ruby-trunk - Bug #9600] sysconf(_SC_GETGR_R_SIZE_MAX) is just a hint for getgrnam_r()

Issue #9600 has been updated by Akira Tanaka.


Off topic.

Yui NARUSE wrote:
> 
> SuSv7 changes it.
> 
> * http://pubs.opengroup.org/onlinepubs/009695399/functions/getgrnam.html v6's getgrnam_r
> * http://pubs.opengroup.org/onlinepubs/9699919799/functions/getgrnam.html v7's getgrnam_r
> * http://pubs.opengroup.org/onlinepubs/9699919799/functions/sysconf.html v7's sysconf

There is no Single Unix Specification version 7 (yet).
The issue number is not the version number.

SUSv3:
| The Single UNIX Specification, Version 3 is made up of the Base Specifications, Issue 6 and
| X/Open Curses, Issue 4, Version 2.
http://www.unix.org/version3/sus_contents.html

SUSv4:
| The Single UNIX Specification uses The Open Group Base Specifications, Issue 7 documentation as its core.
| The documentation is structured as follows:
| * The Base Specifications, Issue 7, composed of:
|   - Base Definitions, Issue 7 (XBD7)
|   - System Interfaces, Issue 7 (XSH7)
|   - Shell and Utilities, Issue 7 (XCU7)
|   - Rationale, Issue 7, (XRAT7) (Informative)
| * X/Open Curses, Issue 7
http://www.unix.org/version4/overview.html



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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-45654

* 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
----------------------------------------
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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