RFR: 8251438: Issues with our POSIX set_signal_handler()

[Thomas Stuefe]

On Mon, 7 Dec 2020 21:45:57 GMT, Gerard Ziemski <gziemski at openjdk.org> wrote:

> This is a fix for a potential issue involving "The storage occupied by sa_handler and sa_sigaction may overlap, and a conforming application shall not use both simultaneously." https://pubs.opengroup.org/onlinepubs/009695399/functions/sigaction.html, when we in fact do assume different storages.

Hi Gerard,

I was confused about the patch. Its fine from a simplification standpoint - putting all those ? expressions into one place - but where were we relying on different storage?

Cheers, Thomas

src/hotspot/os/posix/signals_posix.cpp line 743:

> 741: // Implementation may use the same storage for both the sa_sigaction field and the sa_handler field,
> 742: // so check for "sigAct.sa_flags == SA_SIGINFO"
> 743: static address get_signal_handler(struct sigaction action) {

This copies the structure by value. While the compiler will probably optimize this out, I'd still not do it. Please use 
static address get_signal_handler(const struct sigaction*) 
 
instead.

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Changes requested by stuefe (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/1680