Handle invalid C++ function names in LLD.

Author: cjacek

lld/COFF/Driver.cpp

@@ -714,9 +714,8 @@ Symbol *LinkerDriver::addUndefined(StringRef name, bool aliasEC) {
         Symbol *t = ctx.symtab.addUndefined(saver().save(*mangledName));
         u->setWeakAlias(t, true);
       }
-    } else {
-      std::optional<std::string> demangledName =
-          getArm64ECDemangledFunctionName(name);
+    } else if (std::optional<std::string> demangledName =
+                   getArm64ECDemangledFunctionName(name)) {
       Symbol *us = ctx.symtab.addUndefined(saver().save(*demangledName));
       auto u = dyn_cast<Undefined>(us);
       if (u && !u->weakAlias)

lld/COFF/SymbolTable.cpp

@@ -669,8 +669,11 @@ bool checkLazyECPair(SymbolTable *symtab, StringRef name, InputFile *f) {
   if (std::optional<std::string> mangledName =
           getArm64ECMangledFunctionName(name))
     pairName = std::move(*mangledName);
+  else if (std::optional<std::string> demangledName =
+               getArm64ECDemangledFunctionName(name))
+    pairName = std::move(*demangledName);
   else
-    pairName = *getArm64ECDemangledFunctionName(name);
+    return true;
 
   Symbol *sym = symtab->find(pairName);
   if (!sym)

llvm/lib/IR/Mangler.cpp

@@ -317,7 +317,8 @@ std::optional<std::string> llvm::getArm64ECMangledFunctionName(StringRef Name) {
     // so look for a `@` instead (since we assume that it will not return a
     // qualified type).
     InsertIdx = TrimmedName.find_last_of('@');
-    assert(InsertIdx != StringRef::npos && "Invalid mangled name");
+    if (InsertIdx == StringRef::npos)
+      return std::nullopt;
     InsertIdx += 1;
   }
 

llvm/lib/Object/COFFImportFile.cpp

@@ -756,8 +756,11 @@ Error writeImportLibrary(StringRef ImportName, StringRef Path,
           }
           Name = std::move(*MangledName);
         } else if (!E.Noname && ExportName.empty()) {
-          NameType = IMPORT_NAME_EXPORTAS;
-          ExportName = std::move(*getArm64ECDemangledFunctionName(Name));
+          if (std::optional<std::string> DemangledName =
+                  getArm64ECDemangledFunctionName(Name)) {
+            NameType = IMPORT_NAME_EXPORTAS;
+            ExportName = std::move(*DemangledName);
+          }
         }
       }