ARM32 unwinding on EHABI has issues with static analysis

[kant2002]

Summary

Based on limited understanding these breaks just missing from the original submission time.

[danielkiss]

change looks good but right now it always runs into the assert or failure. I'm wondering why nobody reported yet.
none of the existing tests in llvm runs into the outer while loop.

[compnerd]

That is rather surprising @danielkiss but I think that trying to figure out what happened there while getting this fixed is the better approach here.

[compnerd]

BTW, this might be a good thing to pull into the release branch (CC: @tstellar)

[tstellar]

Can you create a bug for this?

[danielkiss]

not against the fix just made me curious.

[compnerd]

@kant2002 do you have commit rights or do you need someone to commit this on your behalf? @tstellar filled PR51393 to track.

[kant2002]

@comnerd This is my first time contribution. So I assume that I do not have commit rights

[kant2002]

@compnerd I first time made a mistake in you nickname. So I would repeat that that I do not have commit rights. And other question. Where I can look at bugs? I assume in bugzilla, and I should follow standard process described in docs. Correct?

[MaskRay]

You need to provide so that git commit --amend='name <email>' so that the commit can get proper attrition.

You didn't upload the patch via arc diff and the information is unavailable.

[compnerd]

@kant2002 you should be able to see the bug at https://llvm.org/PR51393

libunwind/src/Unwind-EHABI.cpp

_Unwind_Reason_Code ProcessDescriptors(
   while (descriptorWord) {
     // Read descriptor based on # 9.2.
     uint32_t length;
     uint32_t offset;
     switch (format) {
       case Descriptor::LU32:
         descriptor = getNextWord(descriptor, &length);
         descriptor = getNextWord(descriptor, &offset);
+        break;
       case Descriptor::LU16:
         descriptor = getNextNibble(descriptor, &length);
         descriptor = getNextNibble(descriptor, &offset);
+        break;
       default:
         assert(false);
         return _URC_FAILURE;
     }
 
     // See # 9.2 table for decoding the kind of descriptor. It's a 2-bit value.
     Descriptor::Kind kind =
         static_cast<Descriptor::Kind>((length & 0x1) | ((offset & 0x1) << 1));