DWARF: Ignore a compile unit with no abbreviations (#2678)

Such a module can't have valid DIEs, since we have no way to
interpret them.

Also check if DWARF sections from LLVM have contents -
when they are empty the section may exist but have a null
for its data.

Fixes #2673

1 files changed, 5 insertions, 0 deletions

diff --git a/third_party/llvm-project/DWARFVisitor.cpp b/third_party/llvm-project/DWARFVisitor.cpp
index 44bb33b47..ba3d1e0c5 100644
--- a/third_party/llvm-project/DWARFVisitor.cpp
+++ b/third_party/llvm-project/DWARFVisitor.cpp
@@ -59,6 +59,11 @@ template <typename T> void DWARFYAML::VisitorImpl<T>::traverseDebugInfo() {
            DebugInfo.AbbrevDecls[AbbrevEnd].Code) {
       AbbrevEnd++;
     }
+    // XXX BINARYEN If there are no abbreviations, there is nothing to
+    //              do in this unit.
+    if (AbbrevStart == AbbrevEnd) {
+      continue;
+    }
     onStartCompileUnit(Unit);
     if (Unit.Entries.empty()) { // XXX BINARYEN
       continue;