[COFF] Require an explicit -implib option for creating implibs in min…

…gw mode

GNU ld doesn't produce implibs unless explicitly requested.

Differential Revision: https://reviews.llvm.org/D66367

llvm-svn: 369363

lld/COFF/Driver.cpp

@@ -1841,10 +1841,12 @@ void LinkerDriver::link(ArrayRef<const char *> argsArr) {
   }
 
   // Windows specific -- when we are creating a .dll file, we also
-  // need to create a .lib file.
+  // need to create a .lib file. In MinGW mode, we only do that when the
+  // -implib option is given explicitly, for compatibility with GNU ld.
   if (!config->exports.empty() || config->dll) {
     fixupExports();
-    createImportLibrary(/*asLib=*/false);
+    if (!config->mingw || !config->implib.empty())
+      createImportLibrary(/*asLib=*/false);
     assignExportOrdinals();
   }
 

lld/test/COFF/implib-name-mingw.test

@@ -0,0 +1,20 @@
+REQUIRES: x86
+RUN: mkdir -p %t-out
+RUN: llvm-mc -triple x86_64-windows-gnu -filetype obj -o %t-out/object.obj %S/Inputs/object.s
+
+Check that linking without an explicit -implib doesn't produce any implib.
+
+First test that linking without -lldmingw does produce an implib, but when
+adding -lldmingw, it no longer is produced. And when it is explicitly named,
+it is created.
+
+RUN: rm -f %t-out/library.lib
+RUN: lld-link -dll -machine:x64 -def:%S/Inputs/named.def -out:%t-out/library.dll %t-out/object.obj -entry:f -subsystem:console
+RUN: test -f %t-out/library.lib
+
+RUN: rm -f %t-out/library.lib
+RUN: lld-link -lldmingw -dll -machine:x64 -def:%S/Inputs/named.def -out:%t-out/library.dll %t-out/object.obj -entry:f -subsystem:console
+RUN: not test -f %t-out/library.lib
+
+RUN: lld-link -lldmingw -dll -machine:x64 -def:%S/Inputs/named.def -out:%t-out/library.dll %t-out/object.obj -entry:f -subsystem:console -implib:%t-out/library.lib
+RUN: test -f %t-out/library.lib