lld: Include name of output file in "failed to write output" diag

[thakis]

I see this fairly often on Windows, where you can't write to a file that another process – such as a virus scanner – has open: http://45.33.8.238/win/65440/step_4.txt I think it'd be nice to include the file name in the diag.

Come to think of it, maybe we should retry the write after it fails? Might help on Windows. On the other hand, that just hides the problem and doesn't fully fix it, so not sure that's better.

[thakis]

fix test that only runs on windows

[sbc100]

I guess we could make a test that runs elsewhere, by creating a read-only output directory? But maybe not worth it. lgtm either way.

[MaskRay]

lld/test/ELF/link-open-file.test

15

lld/COFF/Writer.cpp

void Writer::run() {
   writeLLDMapFile(ctx);
   writeMapFile(ctx);
 
   if (errorCount())
     return;
 
   ScopedTimer t2(ctx.outputCommitTimer);
   if (auto e = buffer->commit())
-    fatal("failed to write the output file: " + toString(std::move(e)));
+    fatal("failed to write output '" + buffer->getPath() +
+          "': " + toString(std::move(e)));
 }
 
 static StringRef getOutputSectionName(StringRef name) {
   StringRef s = name.split('$').first;
 
   // Treat a later period as a separator for MinGW, for sections like
   // ".ctors.01234".
   return s.substr(0, s.find('.', 1));

lld/ELF/Writer.cpp

if (errorCount())
 
     // Backfill .note.gnu.build-id section content. This is done at last
     // because the content is usually a hash value of the entire output file.
     writeBuildId();
     if (errorCount())
       return;
 
     if (auto e = buffer->commit())
-      error("failed to write to the output file: " + toString(std::move(e)));
+      fatal("failed to write output '" + buffer->getPath() +
+            "': " + toString(std::move(e)));
   }
 }
 
 template <class ELFT, class RelTy>
 static void markUsedLocalSymbolsImpl(ObjFile<ELFT> *file,
                                      llvm::ArrayRef<RelTy> rels) {
   for (const RelTy &rel : rels) {
     Symbol &sym = file->getRelocTargetSym(rel);

lld/MachO/Writer.cpp

void Writer::writeOutputFile() {
   reportPendingUndefinedSymbols();
   if (errorCount())
     return;
   writeSections();
   writeUuid();
   writeCodeSignature();
 
   if (auto e = buffer->commit())
-    error("failed to write to the output file: " + toString(std::move(e)));
+    fatal("failed to write output '" + buffer->getPath() +
+          "': " + toString(std::move(e)));
 }
 
 template <class LP> void Writer::run() {
   treatSpecialUndefineds();
   if (config->entry && needsBinding(config->entry))
     in.stubs->addEntry(config->entry);
 
   // Canonicalization of all pointers to InputSections should be handled by

lld/test/ELF/link-open-file.test

 ## On Windows co-operative applications can be expected to open LLD's output
 ## with FILE_SHARE_DELETE included in the sharing mode. This allows us to link
 ## over the top of an existing file even if it is in use by another application.
 
 # REQUIRES: system-windows, x86
 # RUN: echo '.globl _start; _start:' > %t.s
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-unknown %t.s -o %t.o
 
 ## FILE_SHARE_READ   = 1
 ## FILE_SHARE_WRITE  = 2
 ## FILE_SHARE_DELETE = 4
 
 # RUN:     %python %s %t.o 7
 # RUN: not %python %s %t.o 3 2>&1 | FileCheck %s
-# CHECK: error: failed to write to the output file
+# CHECK: error: failed to write output '{{.*}}': {{.*}}
 
 import contextlib
 import ctypes
 from ctypes import wintypes as w
 import os
 import shutil
 import subprocess
 import platform

lld/wasm/Writer.cpp

void Writer::run() {
   writeHeader();
 
   log("-- writeSections");
   writeSections();
   if (errorCount())
     return;
 
   if (Error e = buffer->commit())
-    fatal("failed to write the output file: " + toString(std::move(e)));
+    fatal("failed to write output '" + buffer->getPath() +
+          "': " + toString(std::move(e)));
 }
 
 // Open a result file.
 void Writer::openFile() {
   log("writing: " + config->outputFile);
 
   Expected<std::unique_ptr<FileOutputBuffer>> bufferOrErr =
       FileOutputBuffer::create(config->outputFile, fileSize,