[ELF] Refactor file I/O error messages

[evgeny777]

Summary

Change position of file name to conform current style.

[ruiu]

I honestly don't think it is an improvement to change this message

error: cannot open foo.o: no such file

to

error: foo.o: cannot open: no such file

because the latter doesn't make sense as a sentence. Why do you want to change that?

[evgeny777]

Like I said earlier, I'd like to have the same format for error messages, so it's easier to parse and change format, when needed.
Those messages have ':' after 'cannot open <file>', which makes the above impossible. Do you have some idea on how to fix this?

[ruiu]

A <file> in "cannot open <file>" is not a location where an error occurred. It's just a result of an error and an error location is somewhere else. For example, imagine that you have a linker script with an INPUT(<file>) command. If we fail to open that file, we want to print out something like this.

error: <linker-script>:308: cannot open <file>: no such file

instead of

error: <file>: cannot open: no such file

So, filename in this case does not indicate where an error happened. We should print out a location that made us open that file instead.

ELF/Driver.cpp

 }
 
 Optional<MemoryBufferRef> LinkerDriver::readFile(StringRef Path) {
   if (Config->Verbose)
     outs() << Path << "\n";
 
   auto MBOrErr = MemoryBuffer::getFile(Path);
   if (auto EC = MBOrErr.getError()) {
-    error(EC, "cannot open " + Path);
+    error(EC, Path + ": cannot open");
     return None;
   }
   std::unique_ptr<MemoryBuffer> &MB = *MBOrErr;
   MemoryBufferRef MBRef = MB->getMemBufferRef();
   OwningMBs.push_back(std::move(MB)); // take MB ownership
 
   if (Cpio)
     Cpio->append(relativeToRoot(Path), MBRef.getBuffer());

ELF/LTO.cpp

 using namespace lld;
 using namespace lld::elf;
 
 // This is for use when debugging LTO.
 static void saveBuffer(StringRef Buffer, const Twine &Path) {
   std::error_code EC;
   raw_fd_ostream OS(Path.str(), EC, sys::fs::OpenFlags::F_None);
   if (EC)
-    error(EC, "cannot create " + Path);
+    error(EC, Path + ": cannot create");
   OS << Buffer;
 }
 
 static void diagnosticHandler(const DiagnosticInfo &DI) {
   SmallString<128> ErrStorage;
   raw_svector_ostream OS(ErrStorage);
   DiagnosticPrinterRawOStream DP(OS);
   DI.print(DP);

ELF/Writer.cpp

template <class ELFT> void Writer<ELFT>::run() {
 
   // 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 EC = Buffer->commit())
-    error(EC, "failed to write to the output file");
+    error(EC, Config->OutputFile + ": failed to write");
 
   // Flush the output streams and exit immediately. A full shutdown
   // is a good test that we are keeping track of all allocated memory,
   // but actually freeing it is a waste of time in a regular linker run.
   if (Config->ExitEarly)
     exitLld(0);
 }
 
for (OutputSectionBase *Sec : OutputSections)
     Sec->writeHeaderTo<ELFT>(++SHdrs);
 }
 
 template <class ELFT> void Writer<ELFT>::openFile() {
   ErrorOr<std::unique_ptr<FileOutputBuffer>> BufferOrErr =
       FileOutputBuffer::create(Config->OutputFile, FileSize,
                                FileOutputBuffer::F_executable);
   if (auto EC = BufferOrErr.getError())
-    error(EC, "failed to open " + Config->OutputFile);
+    error(EC, Config->OutputFile + ": failed to open");
   else
     Buffer = std::move(*BufferOrErr);
 }
 
 template <class ELFT> void Writer<ELFT>::writeSectionsBinary() {
   uint8_t *Buf = Buffer->getBufferStart();
   for (OutputSectionBase *Sec : OutputSections)
     if (Sec->Flags & SHF_ALLOC)

test/ELF/basic.s

 # RUN: ld.lld %t --rsp-quoting=posix @%t.responsefile
 # RUN: llvm-readobj -file-headers -sections -program-headers -symbols %t2 \
 # RUN:   | FileCheck %s
 
 # Test for the response file (Windows quoting style)
 # RUN: echo " c:\blah\foo" > %t.responsefile
 # RUN: not ld.lld --rsp-quoting=windows %t @%t.responsefile 2>&1 | FileCheck \
 # RUN:   %s --check-prefix=WINRSP
-# WINRSP: cannot open c:\blah\foo
+# WINRSP: c:\blah\foo: cannot open
 
 # Test for the response file (invalid quoting style)
 # RUN: not ld.lld --rsp-quoting=patatino %t 2>&1 | FileCheck %s \
 # RUN:   --check-prefix=INVRSP
 # INVRSP: invalid response file quoting: patatino
 
 # RUN: not ld.lld %t.foo -o %t2 2>&1 | \
 # RUN:  FileCheck --check-prefix=MISSING %s
-# MISSING: cannot open {{.*}}.foo: {{[Nn]}}o such file or directory
+# MISSING: {{.*}}.foo: cannot open: {{[Nn]}}o such file or directory
 
 # RUN: not ld.lld -o %t2 2>&1 | \
 # RUN:  FileCheck --check-prefix=NO_INPUT %s
 # NO_INPUT: ld.lld{{.*}}: no input files
 
 # RUN: not ld.lld %t.no.such.file -o %t2 2>&1 | \
 # RUN:  FileCheck --check-prefix=CANNOT_OPEN %s
-# CANNOT_OPEN: cannot open {{.*}}.no.such.file: {{[Nn]}}o such file or directory
+# CANNOT_OPEN: {{.*}}.no.such.file: cannot open: {{[Nn]}}o such file or directory
 
 # RUN: not ld.lld %t -o 2>&1 | FileCheck --check-prefix=NO_O_VAL %s
 # NO_O_VAL: -o: missing argument
 
 # RUN: not ld.lld --foo 2>&1 | FileCheck --check-prefix=UNKNOWN %s
 # UNKNOWN: unknown argument: --foo
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t

test/ELF/driver.test

 # REQUIRES: x86
 
 # RUN: not ld.lld --unknown1 --unknown2 -m foo /no/such/file -lnosuchlib \
 # RUN:   2>&1 | FileCheck -check-prefix=UNKNOWN %s
 
 # UNKNOWN: unknown argument: --unknown1
 # UNKNOWN: unknown argument: --unknown2
 # UNKNOWN: unknown emulation: foo
-# UNKNOWN: cannot open /no/such/file
+# UNKNOWN: /no/such/file: cannot open
 # UNKNOWN: unable to find library -lnosuchlib
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
 # RUN: not ld.lld %t -o /no/such/file 2>&1 | FileCheck -check-prefix=MISSING %s
-# MISSING: failed to open /no/such/file
+# MISSING: /no/such/file: failed to open 
 
 # RUN: ld.lld --help 2>&1 | FileCheck -check-prefix=HELP %s
 # HELP: USAGE:
 
 # RUN: ld.lld --version 2>&1 | FileCheck -check-prefix=VERSION %s
 # VERSION: LLD
 
 # RUN: not ld.lld -v 2>&1 | FileCheck -check-prefix=VERSION %s

 # ERR5: -r and -pie may not be used together
 
 ## Attempt to use -shared and -pie together
 # RUN: not ld.lld -shared -pie %t -o %tfail 2>&1 | FileCheck -check-prefix=ERR6 %s
 # ERR6: -shared and -pie may not be used together
 
 ## "--output=foo" is equivalent to "-o foo".
 # RUN: not ld.lld %t --output=/no/such/file 2>&1 | FileCheck -check-prefix=ERR7 %s
-# ERR7: failed to open /no/such/file
+# ERR7: /no/such/file: failed to open
 
 ## "-output=foo" is equivalent to "-o utput=foo".
 # RUN: not ld.lld %t -output=/no/such/file 2>&1 | FileCheck -check-prefix=ERR8 %s
-# ERR8: failed to open utput=/no/such/file
+# ERR8: utput=/no/such/file: failed to open 
 
 .globl _start
 _start:
   nop

test/ELF/error-limit.test

 RUN: not ld.lld 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 \
 RUN:   21 22 2>&1 | FileCheck -check-prefix=DEFAULT %s
 
-DEFAULT:      cannot open 01
-DEFAULT:      cannot open 20
+DEFAULT:      01: cannot open
+DEFAULT:      20: cannot open
 DEFAULT-NEXT: too many errors emitted, stopping now (use -error-limit=0 to see all errors)
-DEFAULT-NOT:  cannot open 21
+DEFAULT-NOT:  21: cannot open
 
 RUN: not ld.lld -error-limit=5 01 02 03 04 05 06 07 08 09 10 2>&1 \
 RUN:   | FileCheck -check-prefix=LIMIT5 %s
 RUN: not ld.lld -error-limit 5 01 02 03 04 05 06 07 08 09 10 2>&1 \
 RUN:   | FileCheck -check-prefix=LIMIT5 %s
 
-LIMIT5:      cannot open 01
-LIMIT5:      cannot open 05
+LIMIT5:      01: cannot open
+LIMIT5:      05: cannot open
 LIMIT5-NEXT: too many errors emitted, stopping now (use -error-limit=0 to see all errors)
-LIMIT5-NOT:  cannot open 06
+LIMIT5-NOT:  06: cannot open
 
 RUN: not ld.lld -error-limit=0 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 \
 RUN:   16 17 18 19 20 21 22 2>&1 | FileCheck -check-prefix=UNLIMITED %s
 
-UNLIMITED:     cannot open 01
-UNLIMITED:     cannot open 20
-UNLIMITED:     cannot open 21
-UNLIMITED:     cannot open 22
+UNLIMITED:     01: cannot open
+UNLIMITED:     20: cannot open
+UNLIMITED:     21: cannot open
+UNLIMITED:     22: cannot open
 UNLIMITED-NOT: too many errors emitted, stopping now (use -error-limit=0 to see all errors)

test/ELF/invalid-linkerscript.test

 ## Different "echo" commands on Windows interpret quoted strings and
 ## wildcards in similar but different way (On Windows, ARGV tokenization
 ## and wildcard expansion are not done by the shell but by each command.)
 ## Because of that reason, this test fails on some Windows environment.
 ## We can't write quoted strings that are interpreted the same way
 ## by all echo commands. So, we don't want to run this on Windows.
 
 # REQUIRES: shell
 
 # RUN: mkdir -p %t.dir
 
-## Note that we are using "cannot open no-such-file: " as a marker that the
+## Note that we are using "no-such-file: cannot open " as a marker that the
 ## linker keep going when it found an error. That specific error message is not
 ## related to the linker script tests.
 
 # RUN: echo foobar > %t1
 # RUN: not ld.lld %t1 no-such-file 2>&1 | FileCheck -check-prefix=ERR1 %s
 # ERR1: unexpected EOF
-# ERR1: cannot open no-such-file:
+# ERR1: no-such-file: cannot open
 
 # RUN: echo "foo \"bar" > %t2
 # RUN: not ld.lld %t2 no-such-file 2>&1 | FileCheck -check-prefix=ERR2 %s
 # ERR2: unclosed quote
-# ERR2: cannot open no-such-file:
+# ERR2: no-such-file: cannot open 
 
 # RUN: echo "/*" > %t3
 # RUN: not ld.lld %t3 no-such-file 2>&1 | FileCheck -check-prefix=ERR3 %s
 # ERR3: unclosed comment
-# ERR3: cannot open no-such-file:
+# ERR3: no-such-file: cannot open
 
 # RUN: echo "EXTERN (" > %t4
 # RUN: not ld.lld %t4 no-such-file 2>&1 | FileCheck -check-prefix=ERR4 %s
 # ERR4: unexpected EOF
-# ERR4: cannot open no-such-file:
+# ERR4: no-such-file: cannot open
 
 # RUN: echo "EXTERN (" > %t5
 # RUN: not ld.lld %t5 no-such-file 2>&1 | FileCheck -check-prefix=ERR5 %s
 # ERR5: unexpected EOF
-# ERR5: cannot open no-such-file:
+# ERR5: no-such-file: cannot open
 
 # RUN: echo "EXTERN xyz" > %t6
 # RUN: not ld.lld %t6 no-such-file 2>&1 | FileCheck -check-prefix=ERR6 %s
 # ERR6: ( expected, but got xyz
-# ERR6: cannot open no-such-file:
+# ERR6: no-such-file: cannot open
 
 # RUN: echo "INCLUDE /no/such/file" > %t7
 # RUN: not ld.lld %t7 no-such-file 2>&1 | FileCheck -check-prefix=ERR7 %s
 # ERR7: cannot open /no/such/file
-# ERR7: cannot open no-such-file:
+# ERR7: no-such-file: cannot open
 
 # RUN: echo "OUTPUT_FORMAT(x y z)" > %t8
 # RUN: not ld.lld %t8 no-such-file 2>&1 | FileCheck -check-prefix=ERR8 %s
 # ERR8: unexpected token: y
-# ERR8: cannot open no-such-file:
+# ERR8: no-such-file: cannot open

test/ELF/reproduce-error.s

 # Extracting the cpio archive can get over the path limit on windows.
 # REQUIRES: shell
 
 # RUN: rm -rf %t.dir
 # RUN: mkdir -p %t.dir
 # RUN: cd %t.dir
 
 # RUN: not ld.lld --reproduce repro abc -o t 2>&1 | FileCheck %s
-# CHECK: cannot open abc: {{N|n}}o such file or directory
+# CHECK: abc: cannot open: {{N|n}}o such file or directory
 
 # RUN: grep TRAILER repro.cpio
 # RUN: cpio -id < repro.cpio
 # RUN: FileCheck --check-prefix=RSP %s < repro/response.txt
 # RSP: abc
 # RSP: -o t