[ELF] - Do not crash when trying to order --defsym/linker script symbols.

[grimar]

Summary

Currently, we crash because File is null for
such symbols.

[ruiu]

LGTM

[• espindola]

LGTM

ELF/Writer.cpp

if (It == SymbolOrder.end())
       return;
     SymbolOrderEntry &Ent = It->second;
     Ent.Present = true;
 
     if (Config->WarnSymbolOrdering) {
       auto *D = dyn_cast<Defined>(&Sym);
       InputFile *File = Sym.File;
       if (Sym.isUndefined())
-        warn(File->getName() +
+        warn(toString(File) +
              ": unable to order undefined symbol: " + Sym.getName());
       else if (Sym.isShared())
-        warn(File->getName() +
+        warn(toString(File) +
              ": unable to order shared symbol: " + Sym.getName());
       else if (D && !D->Section)
-        warn(File->getName() +
+        warn(toString(File) +
              ": unable to order absolute symbol: " + Sym.getName());
       else if (D && !D->Section->Live)
-        warn(File->getName() +
+        warn(toString(File) +
              ": unable to order discarded symbol: " + Sym.getName());
     }
 
     if (auto *D = dyn_cast<Defined>(&Sym)) {
       if (auto *Sec = dyn_cast_or_null<InputSectionBase>(D->Section)) {
         int &Priority = SectionOrder[cast<InputSectionBase>(Sec->Repl)];
         Priority = std::min(Priority, Ent.Priority);
       }

test/ELF/linkerscript/symbol-ordering-file2.s

+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+
+## Check we do not crash when trying to order linker script symbol.
+
+# RUN: echo "bar" > %t.ord
+# RUN: echo "SECTIONS { bar = 1; }" > %t.script
+# RUN: ld.lld --symbol-ordering-file %t.ord %t.o --script %t.script \
+# RUN:   -o %t.out 2>&1 | FileCheck %s
+# CHECK: warning: <internal>: unable to order absolute symbol: bar
+
+## Check we do not crash when trying to order --defsym symbol.
+
+# RUN: echo "bar" > %t.ord
+# RUN: ld.lld --symbol-ordering-file %t.ord %t.o -defsym=bar=1 \
+# RUN:   -o %t.out 2>&1 | FileCheck %s