Don't crash the frontend if a bad target is given

Provide a chance to emit a diagnostic instead.

rdar://problem/20931800

Swift SVN r28940

include/swift/AST/DiagnosticsFrontend.def

@@ -46,6 +46,12 @@ ERROR(error_no_frontend_args, frontend, none,
 ERROR(error_no_such_file_or_directory,frontend,none,
   "no such file or directory: '%0'", (StringRef))
 
+ERROR(error_unsupported_target_os, frontend, none,
+  "unsupported target OS: '%0'", (StringRef))
+
+ERROR(error_unsupported_target_arch, frontend, none,
+  "unsupported target architecture: '%0'", (StringRef))
+
 ERROR(cannot_open_file,frontend,none,
   "cannot open file '%0' (%1)", (StringRef, StringRef))
 ERROR(cannot_open_serialized_file,frontend,none,

include/swift/Basic/LangOptions.h

@@ -146,7 +146,10 @@ namespace swift {
 
     /// Sets the target we are building for and updates configuration options
     /// to match.
-    void setTarget(llvm::Triple triple);
+    ///
+    /// \returns A pair - the first element is true if the OS was invalid.
+    /// The second element is true if the Arch was invalid.
+    std::pair<bool, bool> setTarget(llvm::Triple triple);
 
     /// Returns the minimum platform version to which code will be deployed.
     ///

lib/Basic/LangOptions.cpp

@@ -36,7 +36,7 @@ bool LangOptions::hasBuildConfigOption(StringRef Name) const {
       != BuildConfigOptions.end();
 }
 
-void LangOptions::setTarget(llvm::Triple triple) {
+std::pair<bool, bool> LangOptions::setTarget(llvm::Triple triple) {
   clearAllTargetConfigOptions();
 
   if (triple.getOS() == llvm::Triple::Darwin &&
@@ -57,6 +57,8 @@ void LangOptions::setTarget(llvm::Triple triple) {
   }
   Target = std::move(triple);
 
+  bool UnsupportedOS = false;
+
   // Set the "os" target configuration.
   if (Target.isMacOSX())
     addTargetConfigOption("os", "OSX");
@@ -70,8 +72,11 @@ void LangOptions::setTarget(llvm::Triple triple) {
     addTargetConfigOption("os", "iOS");
   else if (triple.isOSLinux())
     addTargetConfigOption("os", "Linux");
-  else
+  else {
-    llvm_unreachable("Unsupported target OS");
+    UnsupportedOS = true;
+  }
+
+  bool UnsupportedArch = false;
 
   // Set the "arch" target configuration.
   switch (Target.getArch()) {
@@ -88,12 +93,17 @@ void LangOptions::setTarget(llvm::Triple triple) {
     addTargetConfigOption("arch", "x86_64");
     break;
   default:
-    llvm_unreachable("Unsupported target architecture");
+    UnsupportedArch = true;
   }
 
+  if (UnsupportedOS || UnsupportedArch)
+    return { UnsupportedOS, UnsupportedArch };
+
   // Set the "runtime" target configuration.
   if (EnableObjCInterop)
     addTargetConfigOption("_runtime", "_ObjC");
   else
     addTargetConfigOption("_runtime", "_Native");
+
+  return { false, false };
 }

lib/Frontend/CompilerInvocation.cpp

@@ -720,8 +720,11 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
   Opts.EnableAppExtensionRestrictions |= Args.hasArg(OPT_enable_app_extension);
 
   llvm::Triple Target = Opts.Target;
-  if (const Arg *A = Args.getLastArg(OPT_target))
+  StringRef TargetArg;
+  if (const Arg *A = Args.getLastArg(OPT_target)) {
     Target = llvm::Triple(A->getValue());
+    TargetArg = A->getValue();
+  }
 
   Opts.EnableObjCInterop = Target.isOSDarwin();
   if (auto A = Args.getLastArg(OPT_enable_objc_interop,
@@ -732,9 +735,23 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
 
   // Must be processed after any other language options that could affect
   // target configuration options.
-  Opts.setTarget(Target);
+  bool UnsupportedOS, UnsupportedArch;
+  std::tie(UnsupportedOS, UnsupportedArch) = Opts.setTarget(Target);
 
-  return false;
+  SmallVector<StringRef, 3> TargetComponents;
+  TargetArg.split(TargetComponents, "-");
+
+  if (UnsupportedArch) {
+    auto TargetArgArch = TargetComponents.size() ? TargetComponents[0] : "";
+    Diags.diagnose(SourceLoc(), diag::error_unsupported_target_arch, TargetArgArch);
+  }
+
+  if (UnsupportedOS) {
+    auto TargetArgOS = TargetComponents.size() > 2 ? TargetComponents.back() : "";
+    Diags.diagnose(SourceLoc(), diag::error_unsupported_target_os, TargetArgOS);
+  }
+
+  return UnsupportedOS || UnsupportedArch;
 }
 
 static bool ParseClangImporterArgs(ClangImporterOptions &Opts, ArgList &Args,

test/Frontend/invalid-target.swift

@@ -0,0 +1,5 @@
+// RUN: not %swift %s -target 6502-apple-ios9.0 2>&1 | FileCheck %s -check-prefix=CHECKARCH
+// RUN: not %swift %s -target x86_64-apple-eyeOS 2>&1 | FileCheck %s -check-prefix=CHECKOS
+
+// CHECKARCH: <unknown>:0: error: unsupported target architecture: '6502'
+// CHECKOS: <unknown>:0: error: unsupported target OS: 'eyeOS'