https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111213

--- Comment #3 from mengli ming <dale.mengli.ming at proton dot me> ---
(In reply to David Malcolm from comment #1)
> (In reply to mengli ming from comment #0)
> 
> Thanks for filing this bug.
> 
> > Hi, this case (https://godbolt.org/z/98PMz1KKz) contains an out-of-bound
> > error (stmt: `return arr[9];`). At -O0, the analyzer can report this
> > warning. However, at -O1, -O2, and -O3, the analyzer doesn't report that.
> 
> This is a side-effect of how late the analyzer runs.  Adding
>   -fdump-ipa-analyzer=stdder
> shows that at -O1 and above, the "arr[9]" access is optimized away before
> the analyzer "sees" it.
> 
> See e.g.:
>   https://godbolt.org/z/YjffsMYW4
> 
> My hypothesis is that the optimizer sees the undefined behavior and
> optimizes the function away (but I haven't looked into the details).
> 
> If that's the case, that's a strong argument that the analyzer should run
> earlier. I'm not sure if we have an existing bug about that.

Many thanks!!!

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