[PATCH] D112297: [LTO] Fix assertion failed when flushing bitcode incrementally for LTO output.

[Xu Mingjie via Phabricator via llvm-commits]

Enna1 updated this revision to Diff 382950.
Enna1 edited the summary of this revision.
Enna1 added a comment.
Herald added a subscriber: dexonsmith.

Update patch as @stephan.yichao.zhao @MaskRay suggested.
For both WIN32 and non-WIN32, use the following code to determine `SupportsSeeking `

  off_t loc = ::lseek(FD, 0, SEEK_CUR);
  sys::fs::file_status Status;
  std::error_code EC = status(FD, Status);
  if (EC ||
      Status.type() == sys::fs::file_type::block_file || 
      Status.type() == sys::fs::file_type::character_file) {
    SupportsSeeking = false;
  } else {
    SupportsSeeking = loc != (off_t)-1;
  }


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D112297/new/

https://reviews.llvm.org/D112297

Files:
  lld/test/ELF/lto/emit-llvm_assertion_failure.ll
  llvm/lib/Support/raw_ostream.cpp


Index: llvm/lib/Support/raw_ostream.cpp
===================================================================
--- llvm/lib/Support/raw_ostream.cpp
+++ llvm/lib/Support/raw_ostream.cpp
@@ -643,14 +643,16 @@
 
   // Get the starting position.
   off_t loc = ::lseek(FD, 0, SEEK_CUR);
-#ifdef _WIN32
-  // MSVCRT's _lseek(SEEK_CUR) doesn't return -1 for pipes.
+  // Check if supports seeking
   sys::fs::file_status Status;
   std::error_code EC = status(FD, Status);
-  SupportsSeeking = !EC && Status.type() == sys::fs::file_type::regular_file;
-#else
-  SupportsSeeking = loc != (off_t)-1;
-#endif
+  if (EC ||
+      Status.type() == sys::fs::file_type::block_file ||
+      Status.type() == sys::fs::file_type::character_file) {
+    SupportsSeeking = false;
+  } else {
+    SupportsSeeking = loc != (off_t)-1;
+  }
   if (!SupportsSeeking)
     pos = 0;
   else
Index: lld/test/ELF/lto/emit-llvm_assertion_failure.ll
===================================================================
--- /dev/null
+++ lld/test/ELF/lto/emit-llvm_assertion_failure.ll
@@ -0,0 +1,14 @@
+; Make sure that if --plugin-opt=emit-llvm is enabled and the output
+; is /dev/null, it should not cause a assertion failure in bitcode writer.
+
+; REQUIRES: x86
+
+; RUN: opt -module-hash -module-summary %s -o %t.o
+; RUN: ld.lld --plugin-opt=emit-llvm -mllvm -bitcode-flush-threshold=0 -o /dev/null %t.o
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @main() {
+  ret void
+}


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