[ELF] - Implemented --fatal-warnings option.

[grimar]

Summary

--fatal-warnings: Treat warnings as errors

Since we temporarily switched reporting of multiple declarations of symbols in
version script from error to warning, this one option seems to be usefull to have.
Also it is usefull itself I think.

[• rafael]

LGTM

test/ELF/fatal-warnings.s

6

Maybe check that they print the same message?

ELF/Config.h

struct Configuration {
   bool Demangle = true;
   bool DisableVerify;
   bool DiscardAll;
   bool DiscardLocals;
   bool DiscardNone;
   bool EhFrameHdr;
   bool EnableNewDtags;
   bool ExportDynamic;
+  bool FatalWarnings;
   bool GcSections;
   bool GnuHash = false;
   bool ICF;
   bool Mips64EL = false;
   bool NoGnuUnique;
   bool NoUndefinedVersion;
   bool Pic;
   bool Pie;

ELF/Driver.cpp

void LinkerDriver::readConfigs(opt::InputArgList &Args) {
   Config->Demangle = !Args.hasArg(OPT_no_demangle);
   Config->DisableVerify = Args.hasArg(OPT_disable_verify);
   Config->DiscardAll = Args.hasArg(OPT_discard_all);
   Config->DiscardLocals = Args.hasArg(OPT_discard_locals);
   Config->DiscardNone = Args.hasArg(OPT_discard_none);
   Config->EhFrameHdr = Args.hasArg(OPT_eh_frame_hdr);
   Config->EnableNewDtags = !Args.hasArg(OPT_disable_new_dtags);
   Config->ExportDynamic = Args.hasArg(OPT_export_dynamic);
+  Config->FatalWarnings = Args.hasArg(OPT_fatal_warnings);
   Config->GcSections = Args.hasArg(OPT_gc_sections);
   Config->ICF = Args.hasArg(OPT_icf);
   Config->NoGnuUnique = Args.hasArg(OPT_no_gnu_unique);
   Config->NoUndefinedVersion = Args.hasArg(OPT_no_undefined_version);
   Config->Pie = Args.hasArg(OPT_pie);
   Config->PrintGcSections = Args.hasArg(OPT_print_gc_sections);
   Config->Relocatable = Args.hasArg(OPT_relocatable);
   Config->SaveTemps = Args.hasArg(OPT_save_temps);

ELF/Error.cpp

 bool HasError;
 llvm::raw_ostream *ErrorOS;
 
 void log(const Twine &Msg) {
   if (Config->Verbose)
     llvm::outs() << Msg << "\n";
 }
 
-void warning(const Twine &Msg) { llvm::errs() << Msg << "\n"; }
+void warning(const Twine &Msg) {
+  if (Config->FatalWarnings)
+    error(Msg);
+  else
+    llvm::errs() << Msg << "\n";
+}
 
 void error(const Twine &Msg) {
   *ErrorOS << Msg << "\n";
   HasError = true;
 }
 
 void error(std::error_code EC, const Twine &Prefix) {
   if (EC)

ELF/Options.td

def entry: S<"entry">, MetaVarName<"<entry>">,
   HelpText<"Name of entry point symbol">;
 
 def export_dynamic: F<"export-dynamic">,
   HelpText<"Put symbols in the dynamic symbol table">;
 
 def export_dynamic_symbol: S<"export-dynamic-symbol">,
   HelpText<"Put a symbol in the dynamic symbol table">;
 
+def fatal_warnings: F<"fatal-warnings">,
+  HelpText<"Treat warnings as errors">;
+
 def fini: S<"fini">, MetaVarName<"<symbol>">,
   HelpText<"Specify a finalizer function">;
 
 def hash_style: S<"hash-style">,
   HelpText<"Specify hash style (sysv, gnu or both)">;
 
 def help: F<"help">, HelpText<"Print option help">;
 

 def plugin_eq: J<"plugin=">;
 def plugin_opt: S<"plugin-opt">;
 def plugin_opt_eq: J<"plugin-opt=">;
 
 // Options listed below are silently ignored for now for compatibility.
 def allow_shlib_undefined: F<"allow-shlib-undefined">;
 def define_common: F<"define-common">;
 def detect_odr_violations: F<"detect-odr-violations">;
-def fatal_warnings: F<"fatal-warnings">;
 def no_add_needed: F<"no-add-needed">;
 def no_allow_shlib_undefined: F<"no-allow-shlib-undefined">;
 def no_copy_dt_needed_entries: F<"no-copy-dt-needed-entries">,
   Alias<no_add_needed>;
 def no_dynamic_linker: F<"no-dynamic-linker">;
 def no_fatal_warnings: F<"no-fatal-warnings">;
 def no_mmap_output_file: F<"no-mmap-output-file">;
 def no_warn_common: F<"no-warn-common">;

test/ELF/fatal-warnings.s

+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t1.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %p/Inputs/warn-common.s -o %t2.o
+
+# RUN: ld.lld --warn-common %t1.o %t2.o -o %t1.out
+# RUN: llvm-readobj %t1.out > /dev/null 2>&1
+
+# RUN: not ld.lld --warn-common --fatal-warnings %t1.o %t2.o -o %t2.out 2>&1 | \
+# RUN:   FileCheck -check-prefix=ERR %s
+# ERR: multiple common of
+
+.globl _start
+_start:
+
+.type arr,@object
+.comm arr,4,4