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    SubjectRe: RFC: 'more signals' patch, 2.1.33
    Richard Henderson <> writes:

    > A slightly more difficult situation is what to do with sigsets
    > smaller than the kernel's, at least if we do manage to decouple
    > libc from other libraries from the application. Consider the
    > common idiom:
    > struct sigaction new, old;
    > new = ...
    > sigaction(SIGFOO, &new, &old);
    > ...
    > sigaction(SIGFOO, &old, NULL);
    > which assumes that things are restored intact. But if this bit were
    > in a library and the application was using a larger sigset, then
    > the top bits will be lost.

    I don't think this is a problem. First we introduced a sigset_t which
    is hopefully large enough for the next years in glibc (1024 signals).
    Second, changing the size of the sigset_t etc is an incompatible
    change which is not done without protection. In the above case the
    `sigaction' function will be a wrapper around the sys_xsigaction
    syscall which is in the libc. When some day the size of sigset_t is
    changed and the implementation in the libc has to changed, we'll use
    the symbol versioning of glibc-2.1 and above to hide this. Old
    program will continue to work since the old definition of sigaction
    will still be available for them.

    -- Uli
    ---------------. ,-. Rubensstrasse 5
    Ulrich Drepper \ ,-------------------' \ 76149 Karlsruhe/Germany
    Cygnus Solutions `--' `------------------------

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