[lld][WebAssembly] Early error if output file cannot be created.

[sbc100]

Summary

This matches the behaviour of the ELF driver.

Also move the createFiles to be checkConfig and report `no input
files` there. Again this is mostly to match the structure of the ELF
linker better.

[sbc100]

@ruiu PTAL?

[ruiu]

LGTM

lld/test/wasm/early-exit-for-bad-paths.s

+# RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown %s -o %t.o
+
+# RUN: not wasm-ld %t.o -o does_not_exist/output 2>&1 | \
+# RUN:   FileCheck %s -check-prefixes=NO-DIR-OUTPUT,CHECK
+# RUN: not wasm-ld %t.o -o %s/dir_is_a_file 2>&1 | \
+# RUN:   FileCheck %s -check-prefixes=DIR-IS-OUTPUT,CHECK
+# TODO(sbc): check similar check for -Map file once we add that option
+
+# NO-DIR-OUTPUT: error: cannot open output file does_not_exist/output:
+# DIR-IS-OUTPUT: error: cannot open output file {{.*}}/dir_is_a_file:
+
+# We should exit before doing the actual link. If an undefined symbol error is
+# discovered we haven't bailed out early as expected.
+# CHECK-NOT: undefined_symbol
+
+# RUN: not wasm-ld %t.o -o / 2>&1 | FileCheck %s -check-prefixes=ROOT,CHECK
+# ROOT: error: cannot open output file /
+
+_start:
+    .functype _start () -> ()
+    call undefined_symbol
+    end_function

lld/test/wasm/lto/opt-level.ll

 ; RUN: llvm-as -o %t.o %s
 ; RUN: wasm-ld -o %t0 -e main --lto-O0 %t.o
 ; RUN: obj2yaml %t0 | FileCheck --check-prefix=CHECK-O0 %s
 ; RUN: wasm-ld -o %t2 -e main --lto-O2 %t.o
 ; RUN: obj2yaml %t2 | FileCheck --check-prefix=CHECK-O2 %s
 ; RUN: wasm-ld -o %t2a -e main %t.o
 ; RUN: obj2yaml %t2a | FileCheck --check-prefix=CHECK-O2 %s
 
 ; Reject invalid optimization levels.
 ; RUN: not wasm-ld -o %t3 -e main --lto-O6 %t.o 2>&1 | \
 ; RUN:   FileCheck --check-prefix=INVALID %s
 ; INVALID: invalid optimization level for LTO: 6
 
-; RUN: not wasm-ld -o %t3 -m elf_x86_64 -e main --lto-O-1 %t.o 2>&1 | \
+; RUN: not wasm-ld -o %t3 -e main --lto-O-1 %t.o 2>&1 | \
 ; RUN:   FileCheck --check-prefix=INVALIDNEGATIVE %s
 ; INVALIDNEGATIVE: invalid optimization level for LTO: 4294967295
 
 target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
 target triple = "wasm32-unknown-unknown-wasm"
 
 ; CHECK-O0: Name: foo
 ; CHECK-O2-NOT: Name: foo
 define internal void @foo() {
   ret void
 }
 
 define void @main() {
   call void @foo()
   ret void
 }

lld/test/wasm/responsefile.test

 RUN: llc -filetype=obj -o %t.o %p/Inputs/ret32.ll
 
 RUN: echo "%/t.o -o %/t.wasm -e ret32" > %t.rsp
 RUN: wasm-ld @%t.rsp --initial-memory=655360
 RUN: llvm-readobj --sections %t.wasm | FileCheck %s
 CHECK: InitialPages: 10
 
 RUN: not wasm-ld --rsp-quoting=foobar @%t.rsp 2>&1 | \
 RUN:     FileCheck --check-prefix=INVRSP %s
 INVRSP: invalid response file quoting: foobar
 
 RUN: echo "blah\foo" > %t.rsp
-RUN: not wasm-ld --rsp-quoting=windows @%t.rsp 2>&1 | \
+RUN: not wasm-ld -o a.out --rsp-quoting=windows @%t.rsp 2>&1 | \
 RUN:     FileCheck --check-prefix=WINRSP %s
 WINRSP: error: cannot open blah\foo:
 
 RUN: echo "blah\foo" > %t.rsp
-RUN: not wasm-ld --rsp-quoting=posix @%t.rsp 2>&1 | \
+RUN: not wasm-ld -o a.out --rsp-quoting=posix @%t.rsp 2>&1 | \
 RUN:     FileCheck --check-prefix=POSRSP %s
 POSRSP: error: cannot open blahfoo:

lld/wasm/Driver.cpp

 #include "Config.h"
 #include "InputChunks.h"
 #include "InputGlobal.h"
 #include "MarkLive.h"
 #include "SymbolTable.h"
 #include "Writer.h"
 #include "lld/Common/Args.h"
 #include "lld/Common/ErrorHandler.h"
+#include "lld/Common/Filesystem.h"
 #include "lld/Common/Memory.h"
 #include "lld/Common/Reproduce.h"
 #include "lld/Common/Strings.h"
 #include "lld/Common/Threads.h"
 #include "lld/Common/Version.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/Object/Wasm.h"
 #include "llvm/Option/Arg.h"
for (auto *arg : args) {
     case OPT_whole_archive:
       inWholeArchive = true;
       break;
     case OPT_no_whole_archive:
       inWholeArchive = false;
       break;
     }
   }
+  if (files.empty() && errorCount() == 0)
+    error("no input files");
 }
 
 static StringRef getEntry(opt::InputArgList &args) {
   auto *arg = args.getLastArg(OPT_entry, OPT_no_entry);
   if (!arg) {
     if (args.hasArg(OPT_relocatable))
       return "";
     if (args.hasArg(OPT_shared))
void LinkerDriver::link(ArrayRef<const char *> argsArr) {
   v.push_back("wasm-ld (LLVM option parsing)");
   for (auto *arg : args.filtered(OPT_mllvm))
     v.push_back(arg->getValue());
   cl::ParseCommandLineOptions(v.size(), v.data());
 
   errorHandler().errorLimit = args::getInteger(args, OPT_error_limit, 20);
 
   readConfigs(args);
+
+  createFiles(args);
+  if (errorCount())
+    return;
+
   setConfigs();
   checkOptions(args);
+  if (errorCount())
+    return;
 
   if (auto *arg = args.getLastArg(OPT_allow_undefined_file))
     readImportFile(arg->getValue());
 
-  if (!args.hasArg(OPT_INPUT)) {
-    error("no input files");
+  // Fail early if the output file or map file is not writable. If a user has a
+  // long link, e.g. due to a large LTO link, they do not wish to run it and
+  // find that it failed because there was a mistake in their command-line.
+  if (auto e = tryCreateFile(config->outputFile))
+    error("cannot open output file " + config->outputFile + ": " + e.message());
+  // TODO(sbc): add check for map file too once we add support for that.
+  if (errorCount())
     return;
-  }
 
   // Handle --trace-symbol.
   for (auto *arg : args.filtered(OPT_trace_symbol))
     symtab->trace(arg->getValue());
 
   for (auto *arg : args.filtered(OPT_export))
     config->exportedSymbols.insert(arg->getValue());
 
   createSyntheticSymbols();
 
-  createFiles(args);
-  if (errorCount())
-    return;
-
   // Add all files to the symbol table. This will add almost all
   // symbols that we need to the symbol table.
   for (InputFile *f : files)
     symtab->addFile(f);
   if (errorCount())
     return;
 
   // Handle the `--undefined <sym>` options.