For many non-bugs UBsan is at least as likely to reveal it as -fno-strict-aliasing -fwrapv -fno-aggressive-loop-optimizations so we should tell people to try that before wasting time in Bugzilla.
OK for wwwdocs?
Index: htdocs/bugs/index.html =================================================================== RCS file: /cvs/gcc/wwwdocs/htdocs/bugs/index.html,v retrieving revision 1.116 diff -u -r1.116 index.html --- htdocs/bugs/index.html 5 Jul 2014 21:52:32 -0000 1.116 +++ htdocs/bugs/index.html 6 Oct 2015 10:50:32 -0000 @@ -50,7 +50,11 @@ with <code>gcc -Wall -Wextra</code> and see whether this shows anything wrong with your code. Similarly, if compiling with <code>-fno-strict-aliasing -fwrapv -fno-aggressive-loop-optimizations</code> -makes a difference, your code probably is not correct.</p> +makes a difference, your code probably is not correct. +If compiling with <code>-fsanitize=undefined</code> is supported by your +version of GCC and produces any run-time errors your code is definitely +not correct. +</p> <h2>Summarized bug reporting instructions</h2>