[MinGW] Support --allow-multiple-definition

[Ericson2314]

Summary

We want the Clang CrossWindows toolchain to work with ld.lld and ld.bfd
alike, and it uses this, so we need to support this.

Backport of D69767 for release 8

[mstorsjo]

There's no more releases expected for release 8, and even if there were, I don't think adding a new option to it would be relevant. I.e. keep only D69767 which is intended for master, if I understand things right.

MinGW/Options.td

7

This new multiclass definition seems to be missing in D69767 (and I don't see anything matching in the master branch) - what's up with that?

[ruiu]

As Martin pointed out, I don't think we will have a point release for 8, so if you really need this, please keep this as a local patch.

[Ericson2314]

OK I'll close both backports.

MinGW/Driver.cpp

if (auto *A = Args.getLastArg(OPT_entry)) {
     if (Args.getLastArgValue(OPT_m) == "i386pe" && S.startswith("_"))
       Add("-entry:" + S.substr(1));
     else
       Add("-entry:" + S);
   }
 
   if (auto *A = Args.getLastArg(OPT_subs))
     Add("-subsystem:" + StringRef(A->getValue()));
+  if (Args.hasFlag(OPT_allow_multiple_definition, OPT_no_allow_multiple_definition, false))
+    Add("-force:multiple");
   if (auto *A = Args.getLastArg(OPT_out_implib))
     Add("-implib:" + StringRef(A->getValue()));
   if (auto *A = Args.getLastArg(OPT_stack))
     Add("-stack:" + StringRef(A->getValue()));
   if (auto *A = Args.getLastArg(OPT_output_def))
     Add("-output-def:" + StringRef(A->getValue()));
   if (auto *A = Args.getLastArg(OPT_image_base))
     Add("-base:" + StringRef(A->getValue()));

MinGW/Options.td

 include "llvm/Option/OptParser.td"
 
 class F<string name>: Flag<["--", "-"], name>;
 class J<string name>: Joined<["--", "-"], name>;
 class S<string name>: Separate<["--", "-"], name>;
 
+multiclass B<string name, string help1, string help2> {
+  def NAME: Flag<["--", "-"], name>, HelpText<help1>;
+  def no_ # NAME: Flag<["--", "-"], "no-" # name>, HelpText<help2>;
+}
+
 def L: JoinedOrSeparate<["-"], "L">, MetaVarName<"<dir>">,
   HelpText<"Add a directory to the library search path">;
+
+defm allow_multiple_definition: B<"allow-multiple-definition",
+    "Allow multiple definitions",
+    "Do not allow multiple definitions (default)">;
+
 def dynamicbase: F<"dynamicbase">, HelpText<"Enable ASLR">;
 def entry: S<"entry">, MetaVarName<"<entry>">,
   HelpText<"Name of entry point symbol">;
 def export_all_symbols: F<"export-all-symbols">,
     HelpText<"Export all symbols even if a def file or dllexport attributes are used">;
 def gc_sections: F<"gc-sections">, HelpText<"Remove unused sections">;
 def icf: J<"icf=">, HelpText<"Identical code folding">;
 def image_base: S<"image-base">, HelpText<"Base address of the program">;

test/MinGW/driver.test

 
 RUN: ld.lld -### foo.o -m i386pep -shared FOO.DEF | FileCheck -check-prefix=DEF2 %s
 DEF2: -def:FOO.DEF
 
 RUN: ld.lld -### foo.o -m i386pep -obar.exe | FileCheck -check-prefix=OUT %s
 RUN: ld.lld -### foo.o -m i386pep -o bar.exe | FileCheck -check-prefix=OUT %s
 OUT: -out:bar.exe
 
+RUN: ld.lld -### foo.o -m i386pep --allow-multiple-definitions | FileCheck -check-prefix=FORCE_MULTIPLE %s
+RUN: ld.lld -### foo.o -m i386pep --no-allow-multiple-definitions --allow-multiple-definitions | FileCheck -check-prefix=FORCE_MULTIPLE %s
+FORCE_MULTIPLE: -force:multiple
+
+RUN: ld.lld -### foo.o -m i386pep --no-allow-multiple-definitions | FileCheck -check-prefix=NO_FORCE_MULTIPLE %s
+RUN: ld.lld -### foo.o -m i386pep --allow-multiple-definitions --no-allow-multiple-definitions | FileCheck -check-prefix=NO_FORCE_MULTIPLE %s
+NO_FORCE_MULTIPLE-NOT: -force:multiple
+
 RUN: ld.lld -### foo.o -m i386pep --out-implib bar | FileCheck -check-prefix=IMPLIB %s
 RUN: ld.lld -### foo.o -m i386pep --out-implib=bar | FileCheck -check-prefix=IMPLIB %s
 IMPLIB: -implib:bar
 
 RUN: ld.lld -### foo.o -m i386pep -out-implib bar | FileCheck -check-prefix=NOIMPLIB %s
 NOIMPLIB: -out:ut-implib
 
 RUN: ld.lld -### foo.o -m i386pep -e bar | FileCheck -check-prefix=ENTRY %s