Re: issue: unexpected results in optimizations

["James K. Lowden" <jklowden@schemamania.org>]

On Tue, 12 Dec 2023 09:39:58 +0100
David Brown via Gcc <gcc@gcc.gnu.org> wrote:

> If you have fixed the immediate problems in the code, add the 
> "-fsanitize=undefined" flag before running it.  That will do run-time 
> undefined behaviour checks.

I would like to understand that better, for reasons you might guess.  

-fsanitize is described under Program Instrumentation Options, but much
of the terminology seems to C, and some of the options are documented
to work only with C or C++. 

If it applies to the generated code irrespective of the front-end, then
could the options be described in terms of Generic?  For example,
signed-integer-overflow, bounds, and bounds-strict would seem to be
useful in any language that defines integers and arrays.  I also wonder
if "integer" includes _Float128. 

"-fsanitize" appears only once in the Internals document, under 

	bool TARGET_MEMTAG_CAN_TAG_ADDRESSES

If I knew when contructs were needed for particular options to work, I
could add them to the documentation.  

--jkl