[llvm-lib] Support adding short import library objects with llvm-lib

[mstorsjo]

Summary

This fixes PR 42837.

[hans]

Thanks!

llvm/lib/ToolDrivers/llvm-lib/LibDriver.cpp

197

nit: maybe "import library" should be added to this message now?

llvm/lib/ToolDrivers/llvm-lib/LibDriver.cpp

 }
 
 static void appendFile(std::vector<NewArchiveMember> &Members,
                        COFF::MachineTypes &LibMachine,
                        std::string &LibMachineSource, MemoryBufferRef MB) {
   file_magic Magic = identify_magic(MB.getBuffer());
 
   if (Magic != file_magic::coff_object && Magic != file_magic::bitcode &&
-      Magic != file_magic::archive && Magic != file_magic::windows_resource) {
+      Magic != file_magic::archive && Magic != file_magic::windows_resource &&
+      Magic != file_magic::coff_import_library) {
     llvm::errs() << MB.getBufferIdentifier()
                  << ": not a COFF object, bitcode, archive or resource file\n";
     exit(1);
   }
 
   // If a user attempts to add an archive to another archive, llvm-lib doesn't
   // handle the first archive file as a single file. Instead, it extracts all
   // members from the archive and add them to the second archive. This beahvior
   // is for compatibility with Microsoft's lib command.
   if (Magic == file_magic::archive) {

llvm/test/tools/llvm-lib/implibs.test

+Test that import libraries (and the members thereof) can be added to another
+static library.
+
+RUN: rm -rf %t
+RUN: mkdir -p %t
+
+RUN: echo -e "EXPORTS\nMyFunc" > %t/lib.def
+RUN: llvm-dlltool -m i386:x86-64 -l %t/lib.lib -d %t/lib.def -D lib.dll
+RUN: llvm-lib -out:%t/newlib.lib %t/lib.lib
+
+RUN: llvm-ar t %t/newlib.lib | FileCheck %s
+CHECK: lib.dll