[PATCH] D37772: [LLD] [MinGW] Support dllexport on i386

[Martin Storsjö via Phabricator via llvm-commits]

mstorsjo created this revision.

In MinGW configurations (GCC, or clang with a `*-windows-gnu` target), the -export directives in the object file contains the undecorated symbol name, while it is decorated in MSVC configurations. (On the command line, link.exe takes an undecorated symbol name for the -export argument though.)


https://reviews.llvm.org/D37772

Files:
  COFF/Config.h
  COFF/Driver.cpp
  COFF/Options.td
  MinGW/Driver.cpp
  test/COFF/dllexport-gnu.s


Index: test/COFF/dllexport-gnu.s
===================================================================
--- /dev/null
+++ test/COFF/dllexport-gnu.s
@@ -0,0 +1,19 @@
+# REQEUIRES: x86
+
+# RUN: llvm-mc -triple=i686-windows-gnu %s -filetype=obj -o %t.obj
+
+# RUN: lld-link -mingw -dll -out:%t.dll -entry:main %t.obj -implib:%t.lib
+# RUN: llvm-readobj %t.lib | FileCheck %s
+
+# CHECK: Symbol: __imp__func
+# CHECK: Symbol: _func
+
+.global _main
+.global _func
+.text
+_main:
+  ret
+_func:
+  ret
+.section .drectve
+.ascii "-export:func"
Index: MinGW/Driver.cpp
===================================================================
--- MinGW/Driver.cpp
+++ MinGW/Driver.cpp
@@ -120,6 +120,7 @@
   auto Add = [&](const Twine &S) { LinkArgs.push_back(S.str()); };
 
   Add("lld-link");
+  Add("-mingw");
 
   if (auto *A = Args.getLastArg(OPT_entry)) {
     StringRef S = A->getValue();
Index: COFF/Options.td
===================================================================
--- COFF/Options.td
+++ COFF/Options.td
@@ -104,6 +104,7 @@
 // LLD extensions
 def nopdb : F<"nopdb">, HelpText<"Disable PDB generation for DWARF users">;
 def nosymtab : F<"nosymtab">;
+def mingw : F<"mingw">, HelpText<"Switch to MinGW behaviour where necessary">;
 def msvclto : F<"msvclto">;
 def rsp_quoting : Joined<["--"], "rsp-quoting=">,
   HelpText<"Quoting style for response files, 'windows' (default) or 'posix'">;
Index: COFF/Driver.cpp
===================================================================
--- COFF/Driver.cpp
+++ COFF/Driver.cpp
@@ -234,6 +234,12 @@
       break;
     case OPT_export: {
       Export E = parseExport(Arg->getValue());
+      if (Config->Machine == I386 && Config->MinGW) {
+        if (!isDecorated(E.Name))
+          E.Name = Saver.save("_" + E.Name);
+        if (!E.ExtName.empty() && !isDecorated(E.ExtName))
+          E.ExtName = Saver.save("_" + E.ExtName);
+      }
       E.Directives = true;
       Config->Exports.push_back(E);
       break;
@@ -719,6 +725,10 @@
     return;
   }
 
+  // Handle /mingw early, since it can potentially affect how other
+  // options are handled.
+  Config->MinGW = Args.hasArg(OPT_mingw);
+
   if (auto *Arg = Args.getLastArg(OPT_linkrepro)) {
     SmallString<64> Path = StringRef(Arg->getValue());
     sys::path::append(Path, "repro.tar");
Index: COFF/Config.h
===================================================================
--- COFF/Config.h
+++ COFF/Config.h
@@ -173,6 +173,8 @@
   bool LargeAddressAware = false;
   bool HighEntropyVA = false;
   bool AppContainer = false;
+
+  bool MinGW = false;
 };
 
 extern Configuration *Config;


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