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

[Eric Christopher]

On Mon, Dec 2, 2013 at 4:21 PM, Manman Ren <manman.ren at gmail.com> wrote:
>
>
>
> 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.
>

You seem to be hard coding certain operations leading me to believe
there's some specific format here that you're looking for, but it's
not obvious what it is - are you saying that if you turn off the
verifier we'll crash on certain types of bitcode files that normally
we wouldn't be able to read anyhow since we'd fail verification?

-eric

> 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));
>> > +    }
>> >    }
>> >  }
>> >
>> >
>> > _______________________________________________
>> > llvm-commits mailing list
>> > llvm-commits at cs.uiuc.edu
>> > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>
>