- lld: do not report undefined weak references in shared libraries
  https://github.com/llvm/llvm-project/commit/52bfd2c1ccd86ff813ee6df5a6700690acdd
- add .gnu.warning.SYMBOL support to ld.lld(1)

Index: tools/lld/ELF/InputFiles.cpp
--- tools/lld/ELF/InputFiles.cpp.orig
+++ tools/lld/ELF/InputFiles.cpp
@@ -52,6 +52,8 @@ std::vector<SharedFile *> elf::sharedFiles;
 
 std::unique_ptr<TarWriter> elf::tar;
 
+DenseMap<StringRef, StringRef> elf::gnuWarnings;
+
 // Returns "<internal>", "foo.a(bar.o)" or "baz.o".
 std::string lld::toString(const InputFile *f) {
   if (!f)
@@ -66,6 +68,17 @@ std::string lld::toString(const InputFile *f) {
   return f->toStringCache;
 }
 
+// .gnu.warning.SYMBOL are treated as warning symbols for the given symbol
+void lld::parseGNUWarning(StringRef name, ArrayRef<char> data, size_t size) {
+  if (!name.empty() && name.startswith(".gnu.warning.")) {
+    StringRef wsym = name.substr(13);
+    StringRef s(data.begin());
+    StringRef wng(s.substr(0, size));
+    symtab->insert(wsym)->gwarn = true;
+    gnuWarnings.insert({wsym, wng});
+  }
+}
+
 static ELFKind getELFKind(MemoryBufferRef mb, StringRef archiveName) {
   unsigned char size;
   unsigned char endian;
@@ -647,6 +660,14 @@ void ObjFile<ELFT>::initializeSections(bool ignoreComd
     case SHT_RELA:
     case SHT_NULL:
       break;
+    case SHT_PROGBITS: {
+      this->sections[i] = createInputSection(sec);
+      StringRef name = CHECK(obj.getSectionName(sec, this->sectionStringTable), this);
+      ArrayRef<char> data =
+          CHECK(obj.template getSectionContentsAsArray<char>(sec), this);
+      parseGNUWarning(name, data, sec.sh_size);
+      }
+      break;
     default:
       this->sections[i] = createInputSection(sec);
     }
@@ -1450,6 +1471,9 @@ template <class ELFT> void SharedFile::parse() {
   const ELFFile<ELFT> obj = this->getObj<ELFT>();
   ArrayRef<Elf_Shdr> sections = CHECK(obj.sections(), this);
 
+  StringRef sectionStringTable =
+      CHECK(obj.getSectionStringTable(sections), this);
+
   const Elf_Shdr *versymSec = nullptr;
   const Elf_Shdr *verdefSec = nullptr;
   const Elf_Shdr *verneedSec = nullptr;
@@ -1472,7 +1496,14 @@ template <class ELFT> void SharedFile::parse() {
     case SHT_GNU_verneed:
       verneedSec = &sec;
       break;
+    case SHT_PROGBITS: {
+      StringRef name = CHECK(obj.getSectionName(sec, sectionStringTable), this);
+      ArrayRef<char> data =
+          CHECK(obj.template getSectionContentsAsArray<char>(sec), this);
+      parseGNUWarning(name, data, sec.sh_size);
+      break;
     }
+    }
   }
 
   if (versymSec && numELFSyms == 0) {
@@ -1567,7 +1598,7 @@ template <class ELFT> void SharedFile::parse() {
       Symbol *s = symtab->addSymbol(
           Undefined{this, name, sym.getBinding(), sym.st_other, sym.getType()});
       s->exportDynamic = true;
-      if (s->isUndefined() && !s->isWeak() &&
+      if (s->isUndefined() && sym.getBinding() != STB_WEAK &&
           config->unresolvedSymbolsInShlib != UnresolvedPolicy::Ignore)
         requiredSymbols.push_back(s);
       continue;