[Clang] Improve error for -fsanitize=function/kcfi -mexecute-only incompatibility (#118816)

The current error message when using the `-fsanitize=function
-mexecute-only` flags together points to the target triple as the reason
that `-fsanitize=function` is not allowed to be used, even when the
function sanitizer is otherwise supported on the target when not using
`-mexecute-only`.

The error message is improved to give `-mexecute-only` as the reason for
disallowing `-fsanitize=function` if it was passed to the driver.

Fixes #117974

Author: Il-Capitano

clang/lib/Driver/SanitizerArgs.cpp

@@ -418,8 +418,14 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
                 Add & NotAllowedWithExecuteOnly & ~DiagnosedKinds) {
           if (DiagnoseErrors) {
             std::string Desc = describeSanitizeArg(Arg, KindsToDiagnose);
-            D.Diag(diag::err_drv_argument_not_allowed_with)
-                << Desc << Triple.str();
+            llvm::opt::Arg *A = Args.getLastArgNoClaim(
+                options::OPT_mexecute_only, options::OPT_mno_execute_only);
+            if (A && A->getOption().matches(options::OPT_mexecute_only))
+              D.Diag(diag::err_drv_argument_not_allowed_with)
+                  << Desc << A->getAsString(Args);
+            else
+              D.Diag(diag::err_drv_unsupported_opt_for_target)
+                  << Desc << Triple.str();
           }
           DiagnosedKinds |= KindsToDiagnose;
         }

clang/test/Driver/fsanitize.c

@@ -989,19 +989,25 @@
 // RUN: not %clang --target=x86_64-linux-gnu -fsanitize=undefined,function -mcmodel=large %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-UBSAN-FUNCTION-CODE-MODEL
 // CHECK-UBSAN-FUNCTION-CODE-MODEL: error: invalid argument '-fsanitize=function' only allowed with '-mcmodel=small'
 
-// RUN: not %clang --target=x86_64-sie-ps5 -fsanitize=function %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-UBSAN-FUNCTION
-// RUN: not %clang --target=x86_64-sie-ps5 -fsanitize=undefined -fsanitize=function %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-UBSAN-FUNCTION
-// RUN: not %clang --target=x86_64-sie-ps5 -fsanitize=kcfi %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-UBSAN-KCFI
-// RUN: not %clang --target=x86_64-sie-ps5 -fsanitize=function -fsanitize=kcfi %s -### 2>&1 | FileCheck %s  --check-prefix=CHECK-UBSAN-KCFI --check-prefix=CHECK-UBSAN-FUNCTION
+// RUN: not %clang --target=x86_64-sie-ps5 -fsanitize=function %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-UBSAN-FUNCTION-TARGET
+// RUN: not %clang --target=x86_64-sie-ps5 -fsanitize=undefined -fsanitize=function %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-UBSAN-FUNCTION-TARGET
+// RUN: not %clang --target=x86_64-sie-ps5 -fsanitize=kcfi %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-UBSAN-KCFI-TARGET
+// RUN: not %clang --target=x86_64-sie-ps5 -fsanitize=function -fsanitize=kcfi %s -### 2>&1 | FileCheck %s  --check-prefix=CHECK-UBSAN-KCFI-TARGET --check-prefix=CHECK-UBSAN-FUNCTION-TARGET
 // RUN: %clang --target=x86_64-sie-ps5 -fsanitize=undefined %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-UBSAN-UNDEFINED
 // CHECK-UBSAN-UNDEFINED: "-fsanitize={{((alignment|array-bounds|bool|builtin|enum|float-cast-overflow|integer-divide-by-zero|nonnull-attribute|null|pointer-overflow|return|returns-nonnull-attribute|shift-base|shift-exponent|signed-integer-overflow|unreachable|vla-bound),?){17}"}}
 
-// RUN: not %clang --target=armv6t2-eabi -mexecute-only -fsanitize=function %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-UBSAN-FUNCTION
-// RUN: not %clang --target=armv6t2-eabi -mexecute-only -fsanitize=kcfi %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-UBSAN-KCFI
+// RUN: not %clang --target=armv6t2-eabi -mexecute-only -fsanitize=function %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-UBSAN-FUNCTION-MEXECUTE-ONLY
+// RUN: not %clang --target=armv6t2-eabi -mpure-code -fsanitize=function %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-UBSAN-FUNCTION-MPURE-CODE
+// RUN: not %clang --target=armv6t2-eabi -mexecute-only -fsanitize=kcfi %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-UBSAN-KCFI-MEXECUTE-ONLY
+// RUN: not %clang --target=armv6t2-eabi -mpure-code -fsanitize=kcfi %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-UBSAN-KCFI-MPURE-CODE
 // RUN: %clang --target=armv6t2-eabi -mexecute-only -fsanitize=undefined %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-UBSAN-UNDEFINED-VPTR
 
-// CHECK-UBSAN-KCFI-DAG: error: invalid argument '-fsanitize=kcfi' not allowed with {{('x86_64-sie-ps5'|'armv6t2-unknown-unknown-eabi')}}
-// CHECK-UBSAN-FUNCTION-DAG: error: invalid argument '-fsanitize=function' not allowed with {{('x86_64-sie-ps5'|'armv6t2-unknown-unknown-eabi')}}
+// CHECK-UBSAN-KCFI-TARGET-DAG: error: unsupported option '-fsanitize=kcfi' for target 'x86_64-sie-ps5'
+// CHECK-UBSAN-KCFI-MEXECUTE-ONLY-DAG: error: invalid argument '-fsanitize=kcfi' not allowed with '-mexecute-only'
+// CHECK-UBSAN-KCFI-MPURE-CODE-DAG: error: invalid argument '-fsanitize=kcfi' not allowed with '-mpure-code'
+// CHECK-UBSAN-FUNCTION-TARGET-DAG: error: unsupported option '-fsanitize=function' for target 'x86_64-sie-ps5'
+// CHECK-UBSAN-FUNCTION-MEXECUTE-ONLY-DAG: error: invalid argument '-fsanitize=function' not allowed with '-mexecute-only'
+// CHECK-UBSAN-FUNCTION-MPURE-CODE-DAG: error: invalid argument '-fsanitize=function' not allowed with '-mpure-code'
 // CHECK-UBSAN-UNDEFINED-VPTR: "-fsanitize={{((alignment|array-bounds|bool|builtin|enum|float-cast-overflow|integer-divide-by-zero|nonnull-attribute|null|pointer-overflow|return|returns-nonnull-attribute|shift-base|shift-exponent|signed-integer-overflow|unreachable|vla-bound|vptr),?){18}"}}
 
 // * Test BareMetal toolchain sanitizer support *