[ELF2] --no-undefined flag implemented

[grimar]

Summary

Report unresolved symbol references from regular object files. This is done even if the linker is creating a non-symbolic shared library.

[grimar]

test/elf2/no-undefined.s

12

I`ll remove 2 extra lines and leave only one here. Just didnt notice it.

[ruiu]

ELF/Options.td

39

Remove the newline at end of this line for consistency with other defs.

41

Indentation error.

41–43

Let's make the message a bit shorter: "Report unresolved symbols even if the linker is creating a shared library"

Do not put period at end as other messages don't.

test/elf2/no-undefined.s

6–11

I don't think we really have to test this case. Let's remove that and no-undefined.s.

[grimar]

ELF/Options.td

41

Thats how clang-format handles it i believe. But after your comments I understood that it is not supposed to be used in this file :)

[ruiu]

ELF/Options.td

41

Is it? I've never tried to apply clang-format to .td files, but if that's the case, we may want to follow the style how clang-format does. But even if we want to do, that should be done at once. Please always keep everything as consistent as possible.

[grimar]

Review comments addressed

[ruiu]

LGTM

The commit message should be

[ELF2] Implement --no-undefined flag.

[grimar]

r249064

ELF/Config.h

struct Configuration {
   std::string RPath;
   std::vector<llvm::StringRef> InputSearchPaths;
   bool AllowMultipleDefinition;
   bool DiscardAll;
   bool DiscardLocals;
   bool DiscardNone;
   bool ExportDynamic;
   bool NoInhibitExec;
+  bool NoUndefined;
   bool Shared;
   bool Static = false;
 };
 
 extern Configuration *Config;
 
 } // namespace elf2
 } // namespace lld
 
 #endif

ELF/Driver.cpp

if (auto *Arg = Args.getLastArg(OPT_entry))
     Config->Entry = Arg->getValue();
 
   Config->AllowMultipleDefinition = Args.hasArg(OPT_allow_multiple_definition);
   Config->DiscardAll = Args.hasArg(OPT_discard_all);
   Config->DiscardLocals = Args.hasArg(OPT_discard_locals);
   Config->DiscardNone = Args.hasArg(OPT_discard_none);
   Config->ExportDynamic = Args.hasArg(OPT_export_dynamic);
   Config->NoInhibitExec = Args.hasArg(OPT_noinhibit_exec);
+  Config->NoUndefined = Args.hasArg(OPT_no_undefined);
   Config->Shared = Args.hasArg(OPT_shared);
 
   for (auto *Arg : Args) {
     switch (Arg->getOption().getID()) {
     case OPT_l:
       addFile(searchLibrary(Arg->getValue()));
       break;
     case OPT_INPUT:

ELF/Options.td

def export_dynamic : Flag<["--"], "export-dynamic">,
   HelpText<"Put symbols in the dynamic symbol table">;
 
 def l : Joined<["-"], "l">, MetaVarName<"<libName>">,
   HelpText<"Root name of library to use">;
 
 def noinhibit_exec : Flag<["--"], "noinhibit-exec">,
   HelpText<"Retain the executable output file whenever it is still usable">;
 
+def no_undefined : Flag<["--"], "no-undefined">,
+  HelpText<"Report unresolved symbols even if the linker is creating a shared library">;
+
 def output : Separate<["-"], "o">, MetaVarName<"<path>">,
   HelpText<"Path to file to write output">;
 
 def rpath : Separate<["-"], "rpath">,
   HelpText<"Add a DT_RUNPATH to the output">;
 
 def shared : Flag<["-"], "shared">,
   HelpText<"Build a shared object">;
 
 def sysroot : Joined<["--"], "sysroot=">,

ELF/Writer.cpp

void Writer<ELFT>::scanRelocs(const InputSection<ELFT> &C) {
   }
 }
 
 template <class ELFT>
 static void reportUndefined(const SymbolTable &S, const SymbolBody &Sym) {
   typedef typename ELFFile<ELFT>::Elf_Sym Elf_Sym;
   typedef typename ELFFile<ELFT>::Elf_Sym_Range Elf_Sym_Range;
 
-  if (Config->Shared)
+  if (Config->Shared && !Config->NoUndefined)
     return;
 
   const Elf_Sym &SymE = cast<ELFSymbolBody<ELFT>>(Sym).Sym;
   ELFFileBase *SymFile = nullptr;
 
   for (const std::unique_ptr<ObjectFileBase> &F : S.getObjectFiles()) {
     const auto &File = cast<ObjectFile<ELFT>>(*F);
     Elf_Sym_Range Syms = File.getObj().symbols(File.getSymbolTable());

test/elf2/no-undefined.s

+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
+# RUN: not lld --no-undefined -shared -flavor gnu2 %t -o %t.so 
+# RUN: lld -shared -flavor gnu2 %t -o %t1.so 
+
+.globl _shared
+_shared: 
+  call _unresolved