[cfe-dev] RFC: Implementing -fno-delete-null-pointer-checks in clang

James Courtier-Dutton via cfe-dev cfe-dev at lists.llvm.org
Fri Apr 27 09:24:49 PDT 2018


Hi,

Turning this on its head. Adding a warning saying something like
"Warning: NULL point check being optimized out at line X"  might be
useful.
The developer might spot that and think "Ah! maybe I put that check in
the wrong place!"

Kind Regards

James



On 18 April 2018 at 19:21, Tim Northover via cfe-dev
<cfe-dev at lists.llvm.org> wrote:
> On 18 April 2018 at 18:13, Manoj Gupta via cfe-dev
> <cfe-dev at lists.llvm.org> wrote:
>> Therefore, I would like to implement support for this flag (maybe with a
>> different name),
>
> I'd suggest -mdo-what-i-mean; the whole idea is horribly
> underspecified, and basically rips up the LangRef in favour of a
> nebulous set of good and bad optimizations (probably as dictated by
> the ones that have bitten someone who wrote bad code recently and was
> grumpy enough about it to complain at us).
>
> In particular I'm skeptical that the address space solution actually
> works. What they actually mean is probably not so much about removing
> the icmps, but about the control-flow decisions based on them. And
> LLVM might not be aware that any given conditional branch comes from a
> tainted comparison.
>
> Cheers.
>
> Tim.
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