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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">It may be worth noting that nearly all well-written UNIX applications should set the disposition of SIGPIPE to SIG_IGN. (Preferably using sigaction, simply
because that's now the preferred API, but doing it with signal is essentially equivalent in this case.)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">SIGPIPE is a hack. It exists only to terminate poorly-written programs that could otherwise block a pipeline. See Bach,
<i>The Design of the UNIX Operating System</i>; if memory serves, Bach quotes Dennis Ritchie on this point. SIGPIPE was introduced because some poorly-written programs did not check the return code from write.[1]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Catching SIGPIPE in a custom handler is nearly always the Wrong Thing. The correct approach, 99.9% of the time, is to set the disposition to SIG_IGN and check
the results of each system call.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Personally, I think it's completely acceptable for a library to note in its documentation that the calling program MUST ignore SIGPIPE, or the library may not
function properly. It's arguably OK for a library to check the disposition of SIGPIPE and if it's SIG_DFL, change it to SIG_IGN, on the grounds that the calling program is not well-written so it doesn't deserve to govern its own signal handling; but it's probably
better to just fail in that case, either immediately (with a diagnostic that tells the user that the developer forgot to set the disposition of SIGPIPE) or when a SIGPIPE occurs.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Libraries can't accommodate all forms of invalid behavior. You can do a certain amount of defensive coding, but at some point you're diminishing functionality
for well-behaved applications in order to coddle bad ones. Don't do that.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">[1] There were no send, sendto, or sendmsg calls at the time. Now the argument applies equally to them.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:black">Michael Wojcik</span><span style="font-size:9.0pt;font-family:"Calibri","sans-serif";color:#1F497D">
<br>
</span><span style="font-size:9.0pt;font-family:"Courier New";color:black">Distinguished Engineer</span><span style="font-size:9.0pt;font-family:"Courier New";color:black">, Micro Focus</span><span style="font-size:9.0pt;font-family:"Calibri","sans-serif";color:#1F497D">
</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> openssl-users [mailto:openssl-users-bounces@openssl.org]
<b>On Behalf Of </b>mahesh gs<br>
<b>Sent:</b> Monday, May 01, 2017 23:59<br>
<b>To:</b> openssl-users@openssl.org<br>
<b>Subject:</b> Re: [openssl-users] Query regarding MSG_NOSIGNAL with SSL_Write<o:p></o:p></span></p>
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<p class="MsoNormal">Yes, ours is a library and we do not wish to ignore the signal process wide because the consumer of our library (application) might want to handle the SIGPIPE for there own socket handling.<o:p></o:p></p>
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