[debug_loc] Fix typo in DWARFExpression constructor

Summary:
The positions of the DwarfVersion and AddressSize arguments were
reversed, which caused parsing for dwarf opcodes which contained
address-size-dependent operands (such as DW_OP_addr). Amusingly enough,
none of the address-size asserts fired, as dwarf version was always 4,
which is a valid address size.

I ran into this when constructing weird inputs for the DWARF verifier. I
I add a test case as hand-written dwarf -- I am not sure how to trigger
this differently, as having a DW_OP_addr inside a location list is a
fairly non-standard thing to do.

Fixing this error exposed a bug in the debug_loc.dwo parser, which was
always being constructed with an address size of 0. I fix that as well
by following the pattern in the non-dwo parser of picking up the address
size from the first compile unit (which is technically not correct, but
probably good enough in practice).

Reviewers: JDevlieghere, aprantl, dblaikie

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D45324

llvm-svn: 329381

1 files changed, 7 insertions, 3 deletions

diff --git a/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp b/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
index b3564f030eb..e9f4df6f27c 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
@@ -672,7 +672,7 @@ const DWARFDebugLoc *DWARFContext::getDebugLoc() {
     return Loc.get();
 
   Loc.reset(new DWARFDebugLoc);
-  // assume all compile units have the same address byte size
+  // Assume all compile units have the same address byte size.
   if (getNumCompileUnits()) {
     DWARFDataExtractor LocData(*DObj, DObj->getLocSection(), isLittleEndian(),
                                getCompileUnitAtIndex(0)->getAddressByteSize());
@@ -685,9 +685,13 @@ const DWARFDebugLocDWO *DWARFContext::getDebugLocDWO() {
   if (LocDWO)
     return LocDWO.get();
 
-  DataExtractor LocData(DObj->getLocDWOSection().Data, isLittleEndian(), 0);
   LocDWO.reset(new DWARFDebugLocDWO());
-  LocDWO->parse(LocData);
+  // Assume all compile units have the same address byte size.
+  if (getNumCompileUnits()) {
+    DataExtractor LocData(DObj->getLocDWOSection().Data, isLittleEndian(),
+                          getCompileUnitAtIndex(0)->getAddressByteSize());
+    LocDWO->parse(LocData);
+  }
   return LocDWO.get();
 }