Unverified Commit 1b8ed4ad authored by Daniel Stenberg's avatar Daniel Stenberg
Browse files

libcurl-thread.3: expand somewhat on the NO_SIGNAL motivation 

Multi-threaded applictions basically MUST set CURLOPT_NO_SIGNAL to 1L to
avoid the risk of getting a SIGPIPE.

Either way, a multi-threaded application that uses libcurl/openssl needs
to have a signhandler for or ignore SIGPIPE on its own.

Based on discussions in #2800
Closes #2904
parent 3c7511b9

docs/libcurl/libcurl-thread.3

+9 −3
Original line number Original line Diff line number Diff line
@@ -5,7 +5,7 @@ 
.\" *                            | (__| |_| |  _ <| |___

.\" *                            | (__| |_| |  _ <| |___

.\" *                             \___|\___/|_| \_\_____|

.\" *                             \___|\___/|_| \_\_____|

.\" *

.\" *

.\" * Copyright (C) 2015 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.

.\" * Copyright (C) 2015 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al.

.\" *

.\" *

.\" * This software is licensed as described in the file COPYING, which

.\" * This software is licensed as described in the file COPYING, which

.\" * you should have received as part of this distribution. The terms

.\" * you should have received as part of this distribution. The terms
@@ -79,8 +79,14 @@ all handles. Everything will or might work fine except that timeouts are not 
honored during the DNS lookup - which you can work around by building libcurl

honored during the DNS lookup - which you can work around by building libcurl

with c-ares or threaded-resolver support. c-ares is a library that provides

with c-ares or threaded-resolver support. c-ares is a library that provides

asynchronous name resolves. On some platforms, libcurl simply will not

asynchronous name resolves. On some platforms, libcurl simply will not

function properly multi-threaded unless the \fICURLOPT_NOSIGNAL(3)\fP option is

function properly multi-threaded unless the \fICURLOPT_NOSIGNAL(3)\fP option

set.

is set.



When \fICURLOPT_NOSIGNAL(3)\fP is set to 1L, your application needs to deal

with the risk of a SIGPIPE (that at least the OpenSSL backend can

trigger). Note that setting \fICURLOPT_NOSIGNAL(3)\fP to 0L will not work in a

threaded situation as there will be race where libcurl risks restoring the

former signal handler while another thread should still ignore it.

.IP "Name resolving"

.IP "Name resolving"

\fBgethostby* functions and other system calls.\fP These functions, provided

\fBgethostby* functions and other system calls.\fP These functions, provided

by your operating system, must be thread safe. It is very important that

by your operating system, must be thread safe. It is very important that