<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1252"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">On Aug 24, 2013, at 1:43 PM, Tobias Grosser <<a href="mailto:tobias@grosser.es">tobias@grosser.es</a>> wrote:<br><div><br class="Apple-interchange-newline"><blockquote type="cite"><div style="font-size: 12px; 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;">On 08/24/2013 03:51 AM, Yaron Keren wrote:<br><blockquote type="cite">Hello,<br><br>Attached is a patch I made to make clang warn where division of two integer<br>literals loses precision. For instance:<br><br>double x = 1/2;<br><br>Which results in x being 0. This is not the programmer's intention.<br>While experienced users will know to code 1.0/2 to force floating division,<br>new C/C++ programmers will fall in this trap.<br><br>The patch computes the reminder in the division operation and if only if it<br>is non-zero, warns and suggests a fix.<br><br>This is the first code I write for LLVM so please review it carefully.<br>Specifically, I was not sure whether to create another warning group<br>in DiagnosticSemaKinds.td or reuse an existing one. Maybe the group should<br>be renamed from "DivZero" to "DivProblems".<br></blockquote><br>Wow. This seems really helpful!<br><br>As Matt suggested, please resubmit this patch to cfe-commits and add a test case.<br><br>+//<br>+ // check for integer constant division by integer constant<br><br>Also the comment seems misformatted. Remove the '//', start with an uppercase letter and finish the sentence with a point.<br><br>Also, here is an interesting test case that you may want to consider.<br><br>int foo(float b) {<br><span class="Apple-tab-span" style="white-space: pre;"> </span>float a = 1/2 + b;<br>}<br><br>Suggesting here to transform this into<br><br>int foo(float b) {<br><span class="Apple-tab-span" style="white-space: pre;"> </span>float a = 1.0/2 + b;<br>}<br><br>may not be what the user actually wants, as this promotes the whole expression to 'double'. Possibly the following is more in line.<br><br>int foo(float b) {<br><span class="Apple-tab-span" style="white-space: pre;"> </span>float a = 1.0f/2 + b;<br>}<br><br>Cheers,<br>Tobias<br>_______________________________________________<br>llvm-commits mailing list<br><a href="mailto:llvm-commits@cs.uiuc.edu">llvm-commits@cs.uiuc.edu</a><br><a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits</a></div></blockquote><br></div><div>This seems to have been forgotten, so I guess I’ll adopt it. This adds a test, fixes test failures and adds a new warning group for it. I haven’t yet been able to figure out how get the parent expression to check if it’s a cast to float to add the f in the warning message.</div><div><br></div><div></div></body></html>