<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Jun 23, 2017, at 9:13 PM, David Baraff via swift-users <<a href="mailto:swift-users@swift.org" class="">swift-users@swift.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="">I realize this is slightly centric to iOS, but it irks me that both Apple’s crash report logs and popular platforms like PLCrashReporter can do the hard stuff like give you a stack trace, but are *completely* unable to display the error message from terminating a program via fatalError(), or the error message from, e.g. dying with a bad optional.<br class=""><br class="">Is there *any* to intercept the error messages that from fatalError() and similar like things in swift (bad optionals, invalid array accesses, assertions)? I would think that some sort of a “hook” into these standard error routines would be a good thing.<br class=""><br class="">In my case, if I could simply save that darn error string in a file, i could pick it up when the app next launches and report it along with the rest of the info like the stack/signal, etc.<br class=""><br class="">I’ve been looking through the code in stdlib/public/runtime/Errors.cpp but haven’t found anything promising that lets me jump in there. In my code, I’m likely to write things like<br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>guard let x = … else {<br class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span class="Apple-tab-span" style="white-space:pre"> </span>fatalError(“Data type has payload <T> but is hooked to UI control with intrinsic type <U>”)<br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}<br class=""><br class="">and having that exact string tells me precisely what’s going, far simpler than a stack trace.<br class=""></div></div></blockquote></div><br class=""><div class=""><br class=""></div><div class="">Fatal error messages already get logged three ways:</div><div class=""><br class=""></div><div class="">- Printed to the process's stderr;</div><div class="">- Logged to the system log using asl_log;</div><div class="">- Set as the crash reason for CrashReporter.</div><div class=""><br class=""></div><div class="">The crash messages should thus already be in your crash reports somewhere. See <a href="https://github.com/jckarter/swift/blob/master/stdlib/public/runtime/Errors.cpp#L168" class="">https://github.com/jckarter/swift/blob/master/stdlib/public/runtime/Errors.cpp#L168</a> and <a href="https://github.com/jckarter/swift/blob/master/stdlib/public/runtime/Errors.cpp#L204" class="">https://github.com/jckarter/swift/blob/master/stdlib/public/runtime/Errors.cpp#L204</a> for the relevant runtime source code. cc'ing Greg Parker who probably knows better exactly where these messages end up.</div><div class=""><br class=""></div><div class="">-Joe</div></body></html>