Em sex., 2 de set. de 2022 às 09:01, Justin Pryzby <pryzby@telsasoft.com> escreveu:
On Mon, Aug 29, 2022 at 10:06:55AM +0900, Kyotaro Horiguchi wrote: > At Fri, 26 Aug 2022 10:28:50 -0300, Ranier Vilela <ranier.vf@gmail.com> wrote in > > At function has_matching_range, if variable ranges->nranges == 0, > > we exit quickly with a result equal to false. > > > > This means that nranges can be zero. > > It occurs then that it is possible then to occur an array out of bonds, in > > the initialization of the variable maxvalue. > > So if nranges is equal to zero, there is no need to initialize minvalue and > > maxvalue. > > > > The patch tries to fix it, avoiding possible errors by using maxvalue. > > However it seems that nranges will never be zero, still the fix looks > good to me since it is generally allowed to be zero. I don't find a > similar mistake related to Range.nranges.
I'm not sure, but I *suspect* that compilers usually check ranges->nranges==0 before reading ranges->values[2 * ranges->nranges - 1];
Especially since it's a static function.
Even if they didn't (say, under -O0), values[-1] would probably point to a palloc header, which would be enough to "not crash" before returning one line later.
But +1 to fix this and other issues even if they would never crash.
Thanks Justin.
Based on comments by David, I made a new patch.
To simplify I've included the 0001 in the 0002 patch.
Summary:
1. Once that ranges->nranges is invariant, avoid the loop if ranges->nranges <= 0.
This matches the current behavior.
2. Once that ranges->nsorted is invariant, avoid the loop if ranges->nsorted <= 0.
This matches the current behavior.
3. Remove the invariant cxt from ranges->nsorted loop.
4. Avoid possible overflows when using int to store length strings.
5. Avoid possible out-of-bounds when ranges->nranges == 0.
6. Avoid overhead when using unnecessary StringInfoData to convert Datum a to Text b.
