[llvm-ar] Reapply Fix relative thin archive path handling

Includes a fix for an introduced build failure due to a post c++11 use of std::mismatch. 

This fixes some thin archive relative path issues, paths are shortened where possible and paths are output correctly when using the display table command.

Differential Revision: https://reviews.llvm.org/D59491

llvm-svn: 362484

1 files changed, 8 insertions, 3 deletions

diff --git a/llvm/lib/ToolDrivers/llvm-lib/LibDriver.cpp b/llvm/lib/ToolDrivers/llvm-lib/LibDriver.cpp
index 34a8314..2d44686 100644
--- a/llvm/lib/ToolDrivers/llvm-lib/LibDriver.cpp
+++ b/llvm/lib/ToolDrivers/llvm-lib/LibDriver.cpp
@@ -211,9 +211,14 @@ int llvm::libDriverMain(ArrayRef<const char *> ArgsArr) {
   // llvm-lib uses relative paths for both regular and thin archives, unlike
   // standard GNU ar, which only uses relative paths for thin archives and
   // basenames for regular archives.
-  for (NewArchiveMember &Member : Members)
-    Member.MemberName =
-        Saver.save(computeArchiveRelativePath(OutputPath, Member.MemberName));
+  for (NewArchiveMember &Member : Members) {
+    if (sys::path::is_relative(Member.MemberName)) {
+      Expected<std::string> PathOrErr =
+          computeArchiveRelativePath(OutputPath, Member.MemberName);
+      if (PathOrErr)
+        Member.MemberName = Saver.save(*PathOrErr);
+    }
+  }
 
   if (Error E =
           writeArchive(OutputPath, Members,