[LLD] [MinGW] Support creating DLLs with a def file

[ruiu]

I wonder if MSVC link.exe automatically detects .def files as well. If so, we need to implement the same feature to COFF instead of tweaking the MinGW driver.

[mstorsjo]

In D37761#868521, @ruiu wrote:

I wonder if MSVC link.exe automatically detects .def files as well. If so, we need to implement the same feature to COFF instead of tweaking the MinGW driver.

Doesn't seem so:

$ link -dll -out:lib.dll lib.obj lib.def
Microsoft (R) Incremental Linker Version 14.10.25017.0
Copyright (C) Microsoft Corporation.  All rights reserved.

lib.def : fatal error LNK1107: invalid or corrupt file: cannot read at 0x1E

[ruiu]

Thank you for checking. LGTM.

lld/trunk/MinGW/Driver.cpp

bool mingw::link(ArrayRef<const char *> ArgsArr, raw_ostream &Diag) {
   for (auto *A : Args.filtered(OPT_L))
     SearchPaths.push_back(A->getValue());
 
   StringRef Prefix = "";
   for (auto *A : Args.filtered(OPT_INPUT, OPT_l, OPT_whole_archive,
                                OPT_no_whole_archive)) {
     switch (A->getOption().getID()) {
     case OPT_INPUT:
+      if (StringRef(A->getValue()).endswith(".def"))
+        Add("-def:" + StringRef(A->getValue()));
+      else
         Add(Prefix + StringRef(A->getValue()));
       break;
     case OPT_l:
       Add(Prefix +
           searchLibrary(A->getValue(), SearchPaths, Args.hasArg(OPT_Bstatic)));
       break;
     case OPT_whole_archive:
       Prefix = "-wholearchive:";
       break;

lld/trunk/test/MinGW/driver.test

 ARM64-SAME: -machine:arm64
 ARM64-SAME: -alternatename:__image_base__=__ImageBase
 ARM64-SAME: foo.o
 
 RUN: ld.lld -### foo.o -m i386pep -shared | FileCheck -check-prefix=SHARED %s
 SHARED:      -out:a.dll
 SHARED-SAME: -dll
 
+RUN: ld.lld -### foo.o -m i386pep -shared foo.def | FileCheck -check-prefix=DEF %s
+DEF: -def:foo.def
+
 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 -e bar | FileCheck -check-prefix=ENTRY %s
 RUN: ld.lld -### foo.o -m i386pep --entry bar | FileCheck -check-prefix=ENTRY %s
 ENTRY: -entry:bar
 
 RUN: ld.lld -### foo.o -m i386pep -mllvm bar -mllvm baz | FileCheck -check-prefix=MLLVM %s