<html>
<head>
<style><!--
.hmmessage P
{
margin:0px;
padding:0px
}
body.hmmessage
{
font-size: 12pt;
font-family:Calibri
}
--></style></head>
<body class='hmmessage'><div dir='ltr'>Just a wild guess - is this SIGHUP because stdin/stdout are broken? I.e. the debugger closes its pty's on detach and that causes the signal?<div>What is the behavior on MAC?<br><br><div><hr id="stopSpelling">To: labath@google.com<br>Date: Wed, 30 Mar 2016 14:49:33 -0700<br>CC: lldb-dev@lists.llvm.org<br>Subject: Re: [lldb-dev] SBProcess::Detach kills target<br>From: lldb-dev@lists.llvm.org<br><br>
<style><!--
.ExternalClass .ecxhmmessage P {
padding:0px;
}
.ExternalClass body.ecxhmmessage {
font-size:12pt;
font-family:Calibri;
}
--></style>
<div dir="ltr">Right, my bad. The problem was that when debugger detaches the stdio does not go anywhere so I failed to see my printf.<div><br></div><div>Still, is this how it is supposed to be? I naively assume that if we don't send SIGHUP in attach scenario we should not send it in launch scenario too.</div><div><br></div><div>Thanks,</div><div>Eugene<br><br><div>> From: labath@google.com<br>> Date: Wed, 30 Mar 2016 10:22:33 +0100<br>> Subject: Re: [lldb-dev] SBProcess::Detach kills target<br>> To: eugenebi@hotmail.com<br>> CC: jingham@apple.com; lldb-dev@lists.llvm.org<br>> <br>> So I have made a small test program (which does nothing but spin in a<br>> loop), and indeed it is the SIGHUP that kills it after detach. If the<br>> test program blocks the signal, then it continues running even after<br>> detach:<br>> $ cat a.c<br>> #include <unistd.h><br>> #include <signal.h><br>> <br>> int main() {<br>> signal(SIGHUP, SIG_IGN);<br>> for (;;) sleep(1);<br>> }<br>> $ cc a.c -g<br>> $ ps -A | grep a.out<br>> $ ~/ll/build/dbg/bin/lldb ./a.out<br>> (lldb) target create "./a.out"<br>> Current executable set to './a.out' (x86_64).<br>> (lldb) b 6<br>> Breakpoint 1: where = a.out`main + 19 at a.c:6, address = 0x0000000000400590<br>> (lldb) r<br>> Process 13416 launched: './a.out' (x86_64)<br>> Process 13416 stopped<br>> * thread #1: tid = 13416, 0x0000000000400590 a.out`main + 19 at a.c:6,<br>> name = 'a.out', stop reason = breakpoint 1.1<br>> frame #0: 0x0000000000400590 a.out`main + 19 at a.c:6<br>> 3<br>> 4 int main() {<br>> 5 signal(SIGHUP, SIG_IGN);<br>> -> 6 for (;;) sleep(1);<br>> 7 }<br>> (lldb) detach<br>> Process 13416 detached<br>> (lldb) q<br>> $ ps -A | grep a.out<br>> 13416 ? 00:00:00 a.out<br>> <br>> <br>> On 29 March 2016 at 18:38, Eugene Birukov <eugenebi@hotmail.com> wrote:<br>> > I believe this is not SIGHUP on debugger exit. I am using my own C++ program<br>> > that calls into LLDB API. So, this program is still alive after calling<br>> > SBProcess::Detach() but the target dies. Also, the target intercepts SIGHUP<br>> > to do cleanup before exiting. I put printf there, it was not hit.<br>> The fact whether your program is alive irrelevant. What matters is<br>> that by cleaning up the process structure, we will also close the<br>> master end of the pty used for inferior communication, and this is<br>> what causes the SIGHUP. For that reason you also cannot use a printf<br>> to do diagnostics as the output has nowhere to go. Note that lldb's<br>> behavior here will be different from gdb as gdb does not do stdio<br>> redirection, and has the inferior share the pty with the debugger (in<br>> which case your program will die when you close the terminal window).<br>> <br>> ><br>> > I tried interactive LLDB, the target is not there:<br>> ><br>> > Process 49145 stopped<br>> > * thread #1: tid = 49145, ..., stop reason = signal SIGSTOP<br>> > frame #0: 0x00007ffff6a5bbed libc.so.6 at syscall-template.S:81<br>> > (lldb) detach<br>> > Process 49145 detached<br>> > (lldb) q<br>> > eugene@EUGENEBI-L1:~/tmp$ ps<br>> > PID TTY TIME CMD<br>> > 30714 pts/17 00:00:00 bash<br>> > 49259 pts/17 00:00:00 ps<br>> Note that the inferior will not show up here even if it exists, as ps<br>> will only list the processes with the same tty, but at this point the<br>> inferior process has no tty.<br>> <br>> Good luck with your investigations.<br>> <br>> pl<br></div></div> </div>
<br>_______________________________________________
lldb-dev mailing list
lldb-dev@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev</div></div> </div></body>
</html>