[PATCH] D141145: [fs] Prevent symlink destroying.

[Dmitriy Chestnykh via Phabricator via llvm-commits]

chestnykh created this revision.
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If we open symlink with llvm-strip then
the current behaviour is to destroy it and create
new regular file. This behaviour is different from
the behaviour of binutils strip.
The new behaviour is to modify the real file
and to keep symlink.
PR#59848


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D141145

Files:
  llvm/lib/Support/raw_ostream.cpp
  llvm/test/tools/llvm-objcopy/keep-dso-symlink.test


Index: llvm/test/tools/llvm-objcopy/keep-dso-symlink.test
===================================================================
--- /dev/null
+++ llvm/test/tools/llvm-objcopy/keep-dso-symlink.test
@@ -0,0 +1,7 @@
+# RUN: touch empty.c
+# RUN: clang empty.c -shared -o empty.so.1
+# RUN: ln -sf empty.so.1 empty.so
+# RUN: llvm-strip --strip-unneeded empty.so
+# RUN: [ -L empty.so ] && echo "Still symlink" | FileCheck %s
+
+; CHECK: Still symlink
Index: llvm/lib/Support/raw_ostream.cpp
===================================================================
--- llvm/lib/Support/raw_ostream.cpp
+++ llvm/lib/Support/raw_ostream.cpp
@@ -982,17 +982,30 @@
 
 void buffer_unique_ostream::anchor() {}
 
-Error llvm::writeToOutput(StringRef OutputFileName,
+Error llvm::writeToOutput(StringRef OutputCandidateFileName,
                           std::function<Error(raw_ostream &)> Write) {
-  if (OutputFileName == "-")
+  if (OutputCandidateFileName == "-")
     return Write(outs());
 
-  if (OutputFileName == "/dev/null") {
+  if (OutputCandidateFileName == "/dev/null") {
     raw_null_ostream Out;
     return Write(Out);
   }
 
   unsigned Mode = sys::fs::all_read | sys::fs::all_write | sys::fs::all_exe;
+
+  llvm::SmallString<128> RealPathOfSymlink;
+  if (sys::fs::is_symlink_file(OutputCandidateFileName)) {
+    std::error_code EC =
+        sys::fs::real_path(OutputCandidateFileName, RealPathOfSymlink);
+    if (EC)
+      return errorCodeToError(EC);
+  }
+
+  Twine OutputFileName = RealPathOfSymlink.str().empty()
+                             ? OutputCandidateFileName
+                             : Twine(RealPathOfSymlink);
+
   Expected<sys::fs::TempFile> Temp =
       sys::fs::TempFile::create(OutputFileName + ".temp-stream-%%%%%%", Mode);
   if (!Temp)


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