[PATCH] D66651: Annotate return values of allocation functions with dereferenceable_or_null

Johannes Doerfert via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Wed Aug 28 08:05:30 PDT 2019


jdoerfert added inline comments.


================
Comment at: llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp:4200
+                          Call.getContext(), Op1C->getZExtValue()));
+  } else if (isCallocLikeFn(&Call, TLI) && Op0C && Op1C) {
+    bool Overflow;
----------------
xbolva00 wrote:
> xbolva00 wrote:
> > xbolva00 wrote:
> > > xbolva00 wrote:
> > > > jdoerfert wrote:
> > > > > What if one is NULL but the other not? Will `getWithDereferenceableOrNullBytes(0)` do the right thing?
> > > > Maybe isNullValue confused you. isNullValue means just CstInt->getValue() == 0.
> > > > 
> > > > if Op0C is NULL -> no calloc annotation
> > > > if Op1C is NULL -> no calloc annotation
> > > > 
> > > > if Op0C is '0' -> no annotation; see
> > > > if ((Op0C && Op0C->isNullValue()) || (Op1C && Op1C->isNullValue()))
> > > >     return;
> > > > 
> > > > Same for Op1C.
> > > I will add a comment like
> > > 
> > >   // Bail out if the allocation size is zero.
> > >   if ((Op0C && Op0C->isNullValue()) || (Op1C && Op1C->isNullValue()))
> > >     return;
> > Aha, I know what do you mean.
> > 
> > Hmm, it could work for calloc case - I will look on it.
> eh, no :D
> 
> calloc(1, unknown_var) - We can do nothing in this case ..
`calloc(1, 0)` or `calloc(0, 1)` is the question


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  rL LLVM

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https://reviews.llvm.org/D66651





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