[wwwdocs] Suggest UBsan in https://gcc.gnu.org/bugs/

[wwwdocs] Suggest UBsan in https://gcc.gnu.org/bugs/

[Jonathan Wakely]

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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?

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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>
 

Re: [wwwdocs] Suggest UBsan in https://gcc.gnu.org/bugs/

[Jonathan Wakely]

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On 06/10/15 11:54 +0100, Jonathan Wakely wrote:
>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>
> 

On IRC Markus pointed out that ubsan works in all supported releases,
and that some code that gets ubsan errors still shows real gcc bugs,
so here's an updated patch.

[-- Attachment #2: patch.txt --]
[-- Type: text/x-patch, Size: 802 bytes --]

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 11:15:04 -0000
@@ -50,7 +50,9 @@
 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, or if compiling with <code>-fsanitize=undefined</code>
+produces any run-time errors, then your code is probably not correct.
+</p>
 
 <h2>Summarized bug reporting instructions</h2>
 

Re: [wwwdocs] Suggest UBsan in https://gcc.gnu.org/bugs/

[Gerald Pfeifer]

On Tue, 6 Oct 2015, Jonathan Wakely wrote:
> On IRC Markus pointed out that ubsan works in all supported releases,
> and that some code that gets ubsan errors still shows real gcc bugs,
> so here's an updated patch.

This looks like a nice addition, thank you!

Gerald