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[[!meta title="SA_SIGINFO, SA_SIGACTION"]]

[[!tag open_issue_glibc]]

Note: SA_SIGINFO has now been implemented by Jérémie Koenig.  It will be
uploaded in Debian eglibc 2.13-19.

IRC, #hurd, August / September 2010:

    <giselher> Hy, I came across SA_SIGINFO in cherokee, I have the void sighandler(int num) prototype but how do I add the sa_handler field?
    <pinotree> if SA_SIGACTION is not defined, then you use sa_handler instead of sa_sigaction, and not add SA_SIGINFO in the sa_flags
    <giselher> SA_SIGINFO is not defined
    <pinotree> s/SA_SIGACTION/SA_SIGINFO/ above, yes
    <giselher> K
    <giselher> I am not sure if I fully understand this, there is the  line "act.sa_flags = SA_SIGINFO" and how do I have to change that >_>
    <pinotree> can you paste the source in a pastebin?
    <giselher> k
    <giselher> http://archhurd.pastebin.com/N8BCnG6g at line 790
    <pinotree> something along the lines of http://www.archhurd.pastebin.com/tdpcFD5G
    <pinotree> note that in the handler the siginfo_t parameter is used, which cannot be done if SA_SIGINFO is not defined
    <pinotree> (that code still won't compile, yet)
    <giselher> btw: is there a reason why SA_SIGINFO is not implemented?
    <giselher> the guildlines only say "It's not implemented"
    <azeem> 09:43 < azeem> signal stuff is tricky :-/
    <azeem> basically it was pending on a complete rewrite by Roland, which never occured
    <youpi> I have an almost complete implementation, just not finished yet
    <youpi> (only the siginfo part)
    <azeem> nobody really groked that code for years until youpi showed up, but he added partial support AFAIK, not having much time on his hand
    <azeem> ah, he's here
    <azeem> :)
    <giselher> oh, should I just wait ?
    <youpi> no
    <giselher> k
    <youpi> there are OSes which don't have SA_SIGINFO
    <youpi> just cope with them: use sa_handler instead of sa_sigaction, and don't set SA_SIGINFO
    <youpi> (i.e. replace with 0 in your example)
    <giselher> ok
    <youpi> when SA_SIGINFO becomes available, it'll just be used

IRC, freenode, #hurd, 2011-08-20:

    < youpi> erf, tcpwrappers will need si_pid
    < jkoenig> I could implement it not too far away in the future, we just
      need a version of msg_sig_post() with a siginfo argument or something.
    < youpi> I can also see a lot of packages using SA_SIGINFO for no reason...
    < youpi> (probably copy/pasty code)
    < youpi>   sa.sa_flags = SA_SIGINFO;
    < youpi>   sa.sa_handler = parse_config;
    < youpi> void parse_config(int)
    < youpi> yay
    < youpi>     if(siginf->si_signo == SIGXCPU)
    < youpi>       fprintf(stderr, "Exceeded CPU usage.\n");
    < youpi> ...
    < youpi> jkoenig: actually most package don't actually use the SA_SIGINFO
      they request...
    < youpi> jkoenig: si_pid should get us almost all actually used coverage
    < youpi> I've seen only one example using si_errno
    < jkoenig> ok
    < youpi> oh, it's actually supported by your patch
    < youpi> (errno)
    < jkoenig> but I guess since implementing si_pid will require a new RPC, we
      might as well plan for the rest
    < youpi> jkoenig: indeed
    < jkoenig> youpi, hmm I doubt it's properly filled in in all circumstances?
    < youpi> ok, well, we'll see
    < pinotree> jkoenig: if it can be of help, boost::unit_test queries various
      fields of siginfo_t depending on the signal
    < pinotree> jkoenig: also, pulseaudio uses siginfo_t for remapping faulting
      memory on SIGBUS
    < jkoenig> pinotree, oh ok good to know
    < pinotree> *faulty
    < youpi> jkoenig: well, I guess you had checked that the si_addr field is
      correct in a few simple testcase :)
    < jkoenig> hmm I think so, yes
    < jkoenig> I ran like, "* (char *) 0x12345678;" or something IIRC
    < youpi> ok
    < jkoenig> I seem to remember mach generated SIGBUS instead of SIGSEGV
      depending on the upper bit, or something (I can't quite remember)
    < jkoenig> but when sigsegv was generated si_addr was right.
    < pinotree> jkoenig: (see boost/test/impl/execution_monitor.ipp in boost
      sources)
    < pinotree> maybe you can try the unit tests for boost::unit_tests, if any
      :)
    < pinotree> (while src/pulsecore/memtrap.c in PA)
     * pinotree stops doing MrObvious™