Support non-regular output files.

This patch enables something like "-o /dev/null".
Previouly, it failed because such files cannot be renamed.

Differential Revision: https://reviews.llvm.org/D28010

llvm-svn: 291496

Author: rui314

lld/ELF/Writer.cpp

@@ -1635,10 +1635,12 @@ static void unlinkAsync(StringRef Path) {
   // Path as a new file. If we do that in a different thread, the new
   // thread can remove the new file.
   SmallString<128> TempPath;
-  if (auto EC = sys::fs::createUniqueFile(Path + "tmp%%%%%%%%", TempPath))
-    fatal(EC, "createUniqueFile failed");
-  if (auto EC = sys::fs::rename(Path, TempPath))
-    fatal(EC, "rename failed");
+  if (sys::fs::createUniqueFile(Path + "tmp%%%%%%%%", TempPath))
+    return;
+  if (sys::fs::rename(Path, TempPath)) {
+    sys::fs::remove(TempPath);
+    return;
+  }
 
   // Remove TempPath in background.
   std::thread([=] { ::remove(TempPath.str().str().c_str()); }).detach();

lld/test/ELF/basic.s

@@ -4,6 +4,7 @@
 # RUN: ld.lld %t -o %t2
 # RUN: llvm-readobj -file-headers -sections -program-headers -symbols %t2 \
 # RUN:   | FileCheck %s
+# RUN: ld.lld %t -o /dev/null
 
 # exits with return code 42 on linux
 .globl _start