[llvm-lib] Detect duplicate input files

[ruiu]

Summary

[llvm-lib] Detect duplicate input files

[MaskRay]

Thanks for the follow-up. Test?

[ruiu]

• added a test file

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

 //===- LibDriver.cpp - lib.exe-compatible driver --------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // Defines an interface to a lib.exe-compatible driver that also understands
 // bitcode files. Used by llvm-lib and lld-link /lib.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ToolDrivers/llvm-lib/LibDriver.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/StringSet.h"
 #include "llvm/BinaryFormat/COFF.h"
 #include "llvm/BinaryFormat/Magic.h"
 #include "llvm/Bitcode/BitcodeReader.h"
 #include "llvm/Object/ArchiveWriter.h"
 #include "llvm/Object/COFF.h"
 #include "llvm/Object/WindowsMachineFlag.h"
 #include "llvm/Option/Arg.h"
 #include "llvm/Option/ArgList.h"
if (LibMachine == COFF::IMAGE_FILE_MACHINE_UNKNOWN) {
       llvm::errs() << "unknown /machine: arg " << Arg->getValue() << '\n';
       return 1;
     }
     LibMachineSource =
         std::string(" (from '/machine:") + Arg->getValue() + "' flag)";
   }
 
   std::vector<std::unique_ptr<MemoryBuffer>> MBs;
+  StringSet<> Seen;
   std::vector<NewArchiveMember> Members;
 
   // Create a NewArchiveMember for each input file.
   for (auto *Arg : Args.filtered(OPT_INPUT)) {
     // Find a file
     std::string Path = findInputFile(Arg->getValue(), SearchPaths);
     if (Path.empty()) {
       llvm::errs() << Arg->getValue() << ": no such file or directory\n";
       return 1;
     }
 
+    // Input files are uniquified by pathname. If you specify the exact same
+    // path more than once, all but the first one are ignored.
+    //
+    // Note that there's a loophole in the rule; you can prepend `.\` or
+    // something like that to a path to make it look different, and they are
+    // handled as if they were different files. This behavior is compatible with
+    // Microsoft lib.exe.
+    if (!Seen.insert(Path).second)
+      continue;
+
     // Open a file.
     ErrorOr<std::unique_ptr<MemoryBuffer>> MOrErr =
         MemoryBuffer::getFile(Path, -1, false);
     fatalOpenError(errorCodeToError(MOrErr.getError()), Path);
     MemoryBufferRef MBRef = (*MOrErr)->getMemBufferRef();
 
     // Append a file.
     appendFile(Members, LibMachine, LibMachineSource, MBRef);

llvm/trunk/test/tools/llvm-lib/duplicate.test

+If the same file is specified more than once as an input file,
+llvm-lib should ignore all but the first occurrence of the file.
+
+RUN: rm -rf %t
+RUN: mkdir -p %t
+
+RUN: llvm-mc -triple=x86_64-pc-windows-msvc -filetype=obj -o %t/foo.o %S/Inputs/a.s
+RUN: llvm-mc -triple=x86_64-pc-windows-msvc -filetype=obj -o %t/bar.o %S/Inputs/b.s
+RUN: llvm-lib -out:%t/foo.lib %t/foo.o %t/foo.o %t/bar.o
+
+RUN: llvm-ar t %t/foo.lib | FileCheck %s
+CHECK: foo.o
+CHECK-NOT: foo.o
+CHECK: bar.o