[llvm-ar][libObject] Fix relative paths when nesting thin archives.

Summary:
When adding one thin archive to another, we currently chop off the relative path to the flattened members. For instance, when adding `foo/child.a` (which contains `x.txt`) to `parent.a`, when flattening it we should add it as `foo/x.txt` (which exists) instead of `x.txt` (which does not exist).

As a note, this also undoes the `IsNew` parameter of handling relative paths in r288280. The unit test there still passes.

This was reported as part of testing the kernel build with llvm-ar: https://patchwork.kernel.org/patch/10767545/ (see the second point).

Reviewers: mstorsjo, pcc, ruiu, davide, david2050, inglorion

Reviewed By: ruiu

Subscribers: void, jdoerfert, tpimh, mgorny, hans, nickdesaulniers, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D57842

llvm-svn: 353995

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/ToolDrivers/llvm-lib/LibDriver.cpp b/llvm/lib/ToolDrivers/llvm-lib/LibDriver.cpp
index 3a5b972..34a8314 100644
--- a/llvm/lib/ToolDrivers/llvm-lib/LibDriver.cpp
+++ b/llvm/lib/ToolDrivers/llvm-lib/LibDriver.cpp
@@ -208,6 +208,13 @@ int llvm::libDriverMain(ArrayRef<const char *> ArgsArr) {
 
   // Create an archive file.
   std::string OutputPath = getOutputPath(&Args, Members[0]);
+  // 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));
+
   if (Error E =
           writeArchive(OutputPath, Members,
                        /*WriteSymtab=*/true, object::Archive::K_GNU,