[lld] [lld][ELF] Add --debug-names to create merged .debug_names. (PR #86508)

[David Blaikie via llvm-commits]

================
@@ -2711,6 +2714,606 @@ static uint32_t computeGdbHash(StringRef s) {
   return h;
 }
 
+// 4-byte alignment ensures that values in the hash lookup table and the name
+// table are aligned.
+DebugNamesBaseSection::DebugNamesBaseSection()
+    : SyntheticSection(0, SHT_PROGBITS, 4, ".debug_names") {}
+
+// Get the size of the .debug_names section header in bytes for DWARF32:
+static uint32_t getDebugNamesHeaderSize(uint32_t augmentationStringSize) {
+  return /* unit length */ 4 +
+         /* version */ 2 +
+         /* padding */ 2 +
+         /* CU count */ 4 +
+         /* TU count */ 4 +
+         /* Foreign TU count */ 4 +
+         /* Bucket Count */ 4 +
+         /* Name Count */ 4 +
+         /* Abbrev table size */ 4 +
+         /* Augmentation string size */ 4 +
+         /* Augmentation string */ augmentationStringSize;
+}
+
+void DebugNamesBaseSection::parseDebugNames(
+    InputChunk &inputChunk, OutputChunk &chunk,
+    DWARFDataExtractor &namesExtractor, DataExtractor &strExtractor,
+    function_ref<SmallVector<uint32_t, 0>(
+        const DWARFDebugNames::Header &,
+        const DWARFDebugNames::DWARFDebugNamesOffsets &)>
+        readOffsets) {
+  const LLDDWARFSection namesSec = inputChunk.section;
+  DenseMap<uint32_t, IndexEntry *> offsetMap;
+  for (const DWARFDebugNames::NameIndex &ni : *inputChunk.llvmDebugNames) {
+    NameData &nd = inputChunk.nameData.emplace_back();
+    nd.hdr = ni.getHeader();
+    if (nd.hdr.Format != DwarfFormat::DWARF32) {
+      errorOrWarn(toString(namesSec.sec) + Twine(": unsupported DWARF64"));
+      return;
+    }
+    if (nd.hdr.Version != 5) {
+      errorOrWarn(toString(namesSec.sec) + Twine(": unsupported version ") +
+                  Twine(nd.hdr.Version));
+      return;
+    }
+    const uint32_t dwarfSize =
+        dwarf::getDwarfOffsetByteSize(DwarfFormat::DWARF32);
+    const uint32_t hdrSize =
+        getDebugNamesHeaderSize(nd.hdr.AugmentationStringSize);
+    auto locs = findDebugNamesOffsets(hdrSize, nd.hdr);
+    if (locs.EntriesBase > namesExtractor.getData().size()) {
+      errorOrWarn(toString(namesSec.sec) +
+                  Twine(": index entry is out of bounds"));
----------------
dwblaikie wrote:

This message doesn't seem quite right to me. This is testing that the fixed size parts of the .debug_names are small enough to fit in the available size. It isn't really testing anything about a particular index entry (except maybe the first entry, sort of)

Maybe something like ": insufficient space for name table"? (& optionally could include the minimum size required, based on the parameters in the header)

https://github.com/llvm/llvm-project/pull/86508