[NFC] Fix uninitalized member variable use in ASTReader::ParseTargetOptions()

[schittir]

Summary

Found by Coverity static analysis tool.

[tahonermann]

clang/lib/Serialization/ASTReader.cpp

5890–5892

It is odd that these values aren't preserved by the AST writer. I wonder if that is intentional.

It took me a while, but I eventually found that these data members are assigned via an inclusion of clang/Driver/Options.inc somewhere.

Rather than assigning values here, I think we would be better off adding member initializers in the class definition. But I think we do need to look into why the AST writer isn't preserving the values.

[tahonermann]

clang/include/clang/Basic/TargetOptions.h

48 ↗

(On Diff #507425)

Looks good; this is consistent with the default initialization performed for llvm::TargetOptions::EABIVersion.

91 ↗

(On Diff #507425)

I see that COV_4 is the default as specified in clang/include/clang/Driver/Options.td, but I wonder if we want to duplicate that value here. I'm a bit more inclined to default to COV_None so that we're not trying to maintain the same default in multiple places. I don't know that it matters though.

Perhaps it would make sense to add a "default" option value as is done for EABI? I'm not sure.

[schittir]

Changed CodeObjectVersion default to COV_None

[aaron.ballman]

clang/include/clang/Basic/TargetOptions.h

91 ↗

(On Diff #507425)

I think none makes the most sense to me. This is set via a CC1 option, and the driver doesn't unconditionally set it (https://github.com/llvm/llvm-project/blob/main/clang/lib/Driver/ToolChains/Clang.cpp#L1073), so I think none is safer than assuming CodeObjectVersion is meaningful when it's not set by -cc1. WDYT?

[schittir]

clang/include/clang/Basic/TargetOptions.h

91 ↗

(On Diff #507425)

I agree, and that's why I made the change to none. @tahonermann

[tahonermann]

Changes look good to me. Thanks, Sindhu!

[schittir]

Thank you, @aaron.ballman and @tahonermann for your comments!
This was committed to https://github.com/llvm/llvm-project.git with hash 6f2a865d2f6bc426a61939a0a1acfcb25d5c1a18

clang/lib/Serialization/ASTReader.cpp

bool ASTReader::ParseTargetOptions(const RecordData &Record, bool Complain,
                                    ASTReaderListener &Listener,
                                    bool AllowCompatibleDifferences) {
   unsigned Idx = 0;
   TargetOptions TargetOpts;
   TargetOpts.Triple = ReadString(Record, Idx);
   TargetOpts.CPU = ReadString(Record, Idx);
   TargetOpts.TuneCPU = ReadString(Record, Idx);
   TargetOpts.ABI = ReadString(Record, Idx);
+  TargetOpts.EABIVersion = llvm::EABI::Default;
+  // Initialize CodeObjectVersion with default i.e., 4
+  TargetOpts.CodeObjectVersion = TargetOptions::CodeObjectVersionKind::COV_4;
   for (unsigned N = Record[Idx++]; N; --N) {
     TargetOpts.FeaturesAsWritten.push_back(ReadString(Record, Idx));
   }
   for (unsigned N = Record[Idx++]; N; --N) {
     TargetOpts.Features.push_back(ReadString(Record, Idx));
   }
 
   return Listener.ReadTargetOptions(TargetOpts, Complain,