[ObjectYAML] Fix lifetime issue in dumpDebugLines

[vitalybuka]

llvm/tools/obj2yaml/dwarf2yaml.cpp

288

If we move it outside of the loop tests still work.
However NewOp contains two std::vector first which previously were initialized on every iteration.

290

On a first look it should be safe just

DWARFYAML::LineTableOpcode NewOp = {};

However after that we fail tests:

******************** TEST 'LLVM :: ObjectYAML/MachO/DWARF-debug_line.yaml' FAILED ********************
Script:
--
: 'RUN: at line 1';   /usr/local/google/home/vitalybuka/src/llvm.git/out/a/bin/yaml2obj /usr/local/google/home/vitalybuka/src/llvm.git/llvm-project/llvm/test/ObjectYAML/MachO/DWARF-debug_line.yaml | /usr/local/google/home/vitalybuka/src/llvm.git/out/a/bin/obj2yaml | /usr/local/google/home/vitalybuka/src/llvm.git/out/a/bin/FileCheck /usr/local/google/home/vitalybuka/src/llvm.git/llvm-project/llvm/test/ObjectYAML/MachO/DWARF-debug_line.yaml
--
Exit Code: 1
Command Output (stderr):
--
/usr/local/google/home/vitalybuka/src/llvm.git/llvm-project/llvm/test/ObjectYAML/MachO/DWARF-debug_line.yaml:560:9: error: CHECK: expected string not found in input
#CHECK: Data: 4294971216
        ^
<stdin>:534:2: note: scanning from here
 Data: 0
 ^
<stdin>:546:2: note: possible intended match here
 Data: 11
 ^

So looks like code expects data from the previos iteration.

[beanz]

llvm/tools/obj2yaml/dwarf2yaml.cpp

290

This looks to me like an error in the test case, but I could be wrong. It has been a long time since I dug in DWARF, but I'm pretty sure our YAML is attaching data to opcodes that don't have data fields, and the old code was re-using the values from the previous iteration of the loop, which seems wrong.

[vitalybuka]

proper fix and test update

[vitalybuka]

That's I suspected as well but I din't realize that input of the test was probably generated with that bug :).
Please stamp the patch so we can fix the bot.

llvm/tools/obj2yaml/dwarf2yaml.cpp

if (auto StmtOffset =
         DWARFYAML::File TmpFile;
         if (dumpFileEntry(LineData, Offset, TmpFile))
           DebugLines.Files.push_back(TmpFile);
         else
           break;
       }
 
       const uint64_t LineEnd =
           LineTableLength + *StmtOffset + SizeOfPrologueLength;
+      DWARFYAML::LineTableOpcode NewOp = {};
       while (Offset < LineEnd) {
-        DWARFYAML::LineTableOpcode NewOp;
         NewOp.Opcode = (dwarf::LineNumberOps)LineData.getU8(&Offset);
         if (NewOp.Opcode == 0) {
           auto StartExt = Offset;
           NewOp.ExtLen = LineData.getULEB128(&Offset);
           NewOp.SubOpcode =
               (dwarf::LineNumberExtendedOps)LineData.getU8(&Offset);
           switch (NewOp.SubOpcode) {
           case dwarf::DW_LNE_set_address: