Defect in XSH sigaltstack()

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        Defect report from : Ulrich Drepper , Red Hat, Inc.

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@ page 1352 line 42013 section sigaltstack() objection {ud-sigaltstack}

Problem:

Edition of Specification (Year): 2003

Defect code :  1. Error

The sigalstack() specification current includes in the "shall fail"
area:

[ENOMEM] The size of the alternate stack area is less than MINSIGSTKSZ.


This is a problem in some situation.  Assume a change in the userlevel
definition of MINSGISTKSZ.  The new value is larger than the old one.
The kernel will support either value but new user code will always
use the new, larger value.

If a test suite is now run on such a system it might check that
sigaltstack() fails if the passed stack is MINGSIGSTKSZ-1 in size.  This
call wouldn't fail in this situation.

And for what reason?  There is no legitimate reason.  The requirement
to fail in this case is solely of interest to test suite authors.  If
a program passes a smaller value and it would work from the kernel's point of 
view there is no reason to not allow it.


Action:

Move line 42013 after line 42014 and preceed by a line saying:

The /sigaltstack()/ function may fail if: