[llvm] r196158 - Debug Info: drop debug info via upgrading path if version number does not match.

[Manman Ren]

On Mon, Dec 2, 2013 at 2:07 PM, Eric Christopher <echristo at gmail.com> wrote:

> > Add a helper function getDebugInfoVersionFromModule to return the debug
> info
> > version number for a module.
> >
>
> I think this should be getDebugMetadataVersionFromModule since this
> could be easily confused with the dwarf version that someone has asked
> for.
>

Done in r196172.

>
> > "Verifier/module-flags-1.ll" checks for verification errors.
> > It will seg fault when calling getDebugInfoVersionFromModule because of
> the
> > incorrect format for module flags in the testing case. We make
> > getModuleFlagsMetadata more robust by checking for error conditions.
> >
>
> I'm not sure what's going on here, can you elaborate?
>

We have the code path and the verification path. Code path should not seg
fault when the format of a module flag is incorrect (as in the testing case
Verifier/module-flags-1.ll).
module-flags-1.ll tries to make sure that the verifier dumps the right
error message when the format of a module flag is incorrect.

Before this patch, the code path will seg fault because we don't perform
error checking in the code path as shown below.

Cheers,
Manman


>
> > Modified: llvm/trunk/lib/IR/Module.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Module.cpp?rev=196158&r1=196157&r2=196158&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/lib/IR/Module.cpp (original)
> > +++ llvm/trunk/lib/IR/Module.cpp Mon Dec  2 15:29:56 2013
> > @@ -318,11 +318,16 @@ getModuleFlagsMetadata(SmallVectorImpl<M
> >
> >    for (unsigned i = 0, e = ModFlags->getNumOperands(); i != e; ++i) {
> >      MDNode *Flag = ModFlags->getOperand(i);
> > -    ConstantInt *Behavior = cast<ConstantInt>(Flag->getOperand(0));
> > -    MDString *Key = cast<MDString>(Flag->getOperand(1));
> > -    Value *Val = Flag->getOperand(2);
> > -
>  Flags.push_back(ModuleFlagEntry(ModFlagBehavior(Behavior->getZExtValue()),
> > -                                    Key, Val));
> > +    if (Flag->getNumOperands() >= 3 &&
> isa<ConstantInt>(Flag->getOperand(0)) &&
> > +        isa<MDString>(Flag->getOperand(1))) {
> > +      // Check the operands of the MDNode before accessing the operands.
> > +      // The verifier will actually catch these failures.
> > +      ConstantInt *Behavior = cast<ConstantInt>(Flag->getOperand(0));
> > +      MDString *Key = cast<MDString>(Flag->getOperand(1));
> > +      Value *Val = Flag->getOperand(2);
> > +
>  Flags.push_back(ModuleFlagEntry(ModFlagBehavior(Behavior->getZExtValue()),
> > +                                      Key, Val));
> > +    }
> >    }
> >  }
> >
> >
> > _______________________________________________
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> > llvm-commits at cs.uiuc.edu
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>
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