<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">On Jan 28, 2014, at 12:08 PM, Manuel Klimek <<a href="mailto:klimek@google.com">klimek@google.com</a>> wrote:<br><div><br class="Apple-interchange-newline"><blockquote type="cite"><span style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;">On Tue, Jan 28, 2014 at 2:38 AM, Richard Smith<span class="Apple-converted-space"> </span></span><span dir="ltr" style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><<a href="mailto:metafoo@gmail.com" target="_blank">metafoo@gmail.com</a>></span><span style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;"> </span><span style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;">wrote:</span><br style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><blockquote class="gmail_quote" style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex;"><div class="im"><div>On Mon Jan 27 2014 at 4:51:40 PM, Yuri <<a href="mailto:yuri@rawbw.com" target="_blank">yuri@rawbw.com</a>> wrote:</div><blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex;">On 01/27/2014 16:37, Jean-Daniel Dupas wrote:<br>> If you want to debug/profile clang, you can invoke it directly with the -cc1 flag, and passing the right arguments.<br>><br>> To get the full command line used to invoke the real compilation process, you can use the -### argument:<br>><br>> clang -### -c -emit-llvm c.cpp<br>><br>> For the record, in the early days, the clang driver was a separate binary that used to invoke the compiler (which was called ccc IIRC).<br>> Some time ago, the driver and the compiler were merged into a single clang binary, but it continue to work the same way it used to do. That explains why it executes itself.<br><br>I see.<br>So I wrote up my proposal to make this opt-in:<br><a href="http://llvm.org/bugs/show_bug.cgi?id=18638" target="_blank">http://llvm.org/bugs/show_bug.<u></u>cgi?id=18638</a></blockquote><div><br></div></div><div>I don't think the reasons why we spawn another binary have really been captured in this thread. The biggest reason is that the clang driver accepts multiple files to compile:</div><div><br></div><div> clang foo.c bar.c baz.c -o thing</div><div><br></div><div>... and runs one compile process for each source file (and in this case, one link process for the binary). Crash recovery is just a nice side-effect of having a separate driver and frontend. The main benefit is that we get a consistent execution model regardless of the number of files passed to the driver.</div></blockquote><div style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><br></div><div style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">But nowadays with modules we also have in-process compilation steps of dependent modules without going through the whole driver enchilada, so is this becoming an obsolete argument?</div></blockquote></div><br><div>Clang forking itself remains quite useful for getting test cases for crashers. If the forked clang crashes the parent clang process tries to generate a preprocessed source to serve as a test case. We have found this to be invaluable for users to file useful test cases.</div></body></html>