[clang][PAC] Disallow -pedantic-errors in conjunction with pointer authentication

The __has_extension query for the __ptrauth qualifier returns false
when -pedantic-errors is specified by the developer, which results
in ABI mismatches and potentially ODR violations as well.

The only way to resolve this is to to make it an error to attempt to
use the -pedantic-errors option when targeting a platform where
pointer authentication is present. This may cause compilation issues
for some projects but is better than bad codegen.

Author: ojhunt

clang/lib/Frontend/CompilerInvocation.cpp

@@ -3470,22 +3470,31 @@ static void GeneratePointerAuthArgs(const LangOptions &Opts,
 
 static void ParsePointerAuthArgs(LangOptions &Opts, ArgList &Args,
                                  DiagnosticsEngine &Diags) {
-  Opts.PointerAuthIntrinsics = Args.hasArg(OPT_fptrauth_intrinsics);
-  Opts.PointerAuthCalls = Args.hasArg(OPT_fptrauth_calls);
-  Opts.PointerAuthReturns = Args.hasArg(OPT_fptrauth_returns);
-  Opts.PointerAuthIndirectGotos = Args.hasArg(OPT_fptrauth_indirect_gotos);
-  Opts.PointerAuthAuthTraps = Args.hasArg(OPT_fptrauth_auth_traps);
+  const Arg *PedanticErrors = Args.getLastArgNoClaim(OPT_pedantic_errors);
+  auto GetAndCheckPointerAuthArg = [&](driver::options::ID Option) {
+    Arg *OptionArg = Args.getLastArg(Option);
+    if (OptionArg && PedanticErrors) {
+        Diags.Report(diag::err_drv_incompatible_options)
+            << OptionArg->getSpelling() << PedanticErrors->getSpelling();
+    }
+    return OptionArg != nullptr;
+  };
+  Opts.PointerAuthIntrinsics = GetAndCheckPointerAuthArg(OPT_fptrauth_intrinsics);
+  Opts.PointerAuthCalls = GetAndCheckPointerAuthArg(OPT_fptrauth_calls);
+  Opts.PointerAuthReturns = GetAndCheckPointerAuthArg(OPT_fptrauth_returns);
+  Opts.PointerAuthIndirectGotos = GetAndCheckPointerAuthArg(OPT_fptrauth_indirect_gotos);
+  Opts.PointerAuthAuthTraps = GetAndCheckPointerAuthArg(OPT_fptrauth_auth_traps);
   Opts.PointerAuthVTPtrAddressDiscrimination =
-      Args.hasArg(OPT_fptrauth_vtable_pointer_address_discrimination);
+      GetAndCheckPointerAuthArg(OPT_fptrauth_vtable_pointer_address_discrimination);
   Opts.PointerAuthVTPtrTypeDiscrimination =
-      Args.hasArg(OPT_fptrauth_vtable_pointer_type_discrimination);
+      GetAndCheckPointerAuthArg(OPT_fptrauth_vtable_pointer_type_discrimination);
   Opts.PointerAuthTypeInfoVTPtrDiscrimination =
-      Args.hasArg(OPT_fptrauth_type_info_vtable_pointer_discrimination);
+      GetAndCheckPointerAuthArg(OPT_fptrauth_type_info_vtable_pointer_discrimination);
   Opts.PointerAuthFunctionTypeDiscrimination =
-      Args.hasArg(OPT_fptrauth_function_pointer_type_discrimination);
-  Opts.PointerAuthInitFini = Args.hasArg(OPT_fptrauth_init_fini);
+      GetAndCheckPointerAuthArg(OPT_fptrauth_function_pointer_type_discrimination);
+  Opts.PointerAuthInitFini = GetAndCheckPointerAuthArg(OPT_fptrauth_init_fini);
   Opts.PointerAuthInitFiniAddressDiscrimination =
-      Args.hasArg(OPT_fptrauth_init_fini_address_discrimination);
+      GetAndCheckPointerAuthArg(OPT_fptrauth_init_fini_address_discrimination);
 }
 
 /// Check if input file kind and language standard are compatible.
@@ -4895,6 +4904,11 @@ bool CompilerInvocation::CreateFromArgsImpl(
   InputKind DashX = Res.getFrontendOpts().DashX;
   ParseTargetArgs(Res.getTargetOpts(), Args, Diags);
   llvm::Triple T(Res.getTargetOpts().Triple);
+  if (const Arg *PedanticErrors =  Args.getLastArgNoClaim(OPT_pedantic_errors);
+     PedanticErrors && T.isArm64e()) {
+      Diags.Report(diag::err_drv_unsupported_opt_for_target)
+          << PedanticErrors->getSpelling() << T.str();
+  }
   ParseHeaderSearchArgs(Res.getHeaderSearchOpts(), Args, Diags,
                         Res.getFileSystemOpts().WorkingDir);
   ParseAPINotesArgs(Res.getAPINotesOpts(), Args, Diags);

clang/test/Driver/aarch64-ptrauth-pedantic-errors.c

@@ -0,0 +1,26 @@
+// REQUIRES: aarch64-registered-target
+
+// RUN: not %clang  -pedantic-errors --target=aarch64 -fptrauth-intrinsics %s -c  2>&1 | FileCheck %s
+// RUN: not %clang  -pedantic-errors --target=aarch64 -fptrauth-calls %s -c  2>&1 | FileCheck %s
+// RUN: not %clang  -pedantic-errors --target=aarch64 -fptrauth-returns %s -c  2>&1 | FileCheck %s
+// RUN: not %clang  -pedantic-errors --target=aarch64 -fptrauth-indirect-gotos %s -c  2>&1 | FileCheck %s
+// RUN: not %clang  -pedantic-errors --target=aarch64 -fptrauth-auth-traps %s -c  2>&1 | FileCheck %s
+// RUN: not %clang  -pedantic-errors --target=aarch64 -fptrauth-vtable-pointer-address-discrimination %s -c  2>&1 | FileCheck %s
+// RUN: not %clang  -pedantic-errors --target=aarch64 -fptrauth-vtable-pointer-type-discrimination %s -c  2>&1 | FileCheck %s
+// RUN: not %clang  -pedantic-errors --target=aarch64 -fptrauth-function-pointer-type-discrimination %s -c  2>&1 | FileCheck %s
+// RUN: not %clang  -pedantic-errors --target=aarch64 -fptrauth-init-fini %s -c  2>&1 | FileCheck %s
+// RUN: not %clang  -pedantic-errors --target=aarch64 -fptrauth-init-fini-address-discrimination %s -c  2>&1 | FileCheck %s
+// RUN: not %clang  -pedantic-errors --target=arm64e %s -c  2>&1 | FileCheck %s --check-prefix ARM64E_TRIPLE
+// RUN: not %clang  -pedantic-errors --target=arm64e-apple-macosx10.0 %s -c  2>&1 | FileCheck %s --check-prefix ARM64E_MACOS_TRIPLE
+// RUN: not %clang  -pedantic-errors -arch arm64e %s -c  2>&1 | FileCheck %s --check-prefix ARM64E_ARCH
+
+int i;
+
+// CHECK: error: the combination of '{{.*}}' and '-pedantic-errors' is incompatible
+// ARM64E_TRIPLE: error: unsupported option '-pedantic-errors' for target 'arm64e'
+// ARM64E_MACOS_TRIPLE: error: unsupported option '-pedantic-errors' for target 'arm64e-apple-macosx10.0.0'
+
+// We have a trailing 'arm64e with no closing ' as the full triple is inferred from the host
+// which we don't care about, and don't want to specify as we're wanting to ensure that *just*
+// using '-arch arm64e' is sufficient
+// ARM64E_ARCH: error: unsupported option '-pedantic-errors' for target 'arm64e