fixup! Reject function protos that have different cfi_salt values.

Author: bwendling

clang/lib/Sema/SemaType.cpp

@@ -7943,6 +7943,10 @@ static bool handleFunctionTypeAttr(TypeProcessingState &state, ParsedAttr &attr,
   }
 
   if (attr.getKind() == ParsedAttr::AT_CFISalt) {
+    if (attr.getNumArgs() == 0)
+      return true;
+
+    // Delay if this is not a function type.
     StringRef Argument;
     if (!S.checkStringLiteralArgumentAttr(attr, 0, Argument))
       return false;
@@ -7952,6 +7956,9 @@ static bool handleFunctionTypeAttr(TypeProcessingState &state, ParsedAttr &attr,
       return false;
 
     const auto *FnTy = unwrapped.get()->getAs<FunctionProtoType>();
+    if (!FnTy)
+      return true;
+
     FunctionProtoType::ExtProtoInfo EPI = FnTy->getExtProtoInfo();
     EPI.ExtraAttributeInfo.CFISalt = Argument;
 

clang/test/Sema/attr-cfi-salt.c

@@ -2,17 +2,20 @@
 
 #define __cfi_salt(S) __attribute__((cfi_salt(S)))
 
+int bad1() __cfi_salt();
+    // expected-error@-1{{'cfi_salt' attribute takes one argument}}
+int bad2() __cfi_salt(42);
+    // expected-error@-1{{expected string literal as argument of 'cfi_salt' attribute}}
+
 int foo(int a, int b) __cfi_salt("pepper"); // ok
 int foo(int a, int b) __cfi_salt("pepper"); // ok
 
 typedef int (*bar_t)(void) __cfi_salt("pepper"); // ok
 typedef int (*bar_t)(void) __cfi_salt("pepper"); // ok
 
-#if 0
-// FIXME: These should fail.
-int b(void) __cfi_salt("salt 'n") __cfi_salt("pepper");
-bar_t bar_fn __cfi_salt("salt 'n");
-#endif
+// FIXME: Should we allow this?
+// int b(void) __cfi_salt("salt 'n") __cfi_salt("pepper");
+// bar_t bar_fn __cfi_salt("salt 'n");
 
 int baz __cfi_salt("salt");
     // expected-warning@-1{{'cfi_salt' only applies to function types}}
@@ -36,3 +39,12 @@ typedef int (*quux_t)(void) __cfi_salt("salt 'n");
     // expected-note@-1{{previous definition is here}}
 typedef int (*quux_t)(void) __cfi_salt("pepper");
     // expected-error@-1{{typedef redefinition with different type}}
+
+void func(int a) __cfi_salt("pepper");
+    // expected-note@-1{{previous declaration is here}}
+void func(int a) { }
+    // expected-error@-1{{conflicting types for 'func'}}
+
+void func2(int) [[clang::cfi_salt("test")]];
+void func2(int a) { }
+void (*fp)(int) = func2;