Revert "Diagnose incorrect use of scoped enumerations in format strings"

This reverts commit 3632e2f.

Author: porglezomp

clang/docs/ReleaseNotes.rst

@@ -672,11 +672,6 @@ Bug Fixes in This Version
   (`#50244 <https://github.com/llvm/llvm-project/issues/50244>`_).
 - Apply ``-fmacro-prefix-map`` to anonymous tags in template arguments
   (`#63219 <https://github.com/llvm/llvm-project/issues/63219>`_).
-- Clang now properly diagnoses format string mismatches involving scoped
-  enumeration types. A scoped enumeration type is not promoted to an integer
-  type by the default argument promotions, and thus this is UB. Clang's
-  behavior now matches GCC's behavior in C++.
-  (`#38717 <https://github.com/llvm/llvm-project/issues/38717>`_).
 - Fixed a failing assertion when implicitly defining a function within a GNU
   statement expression that appears outside of a function block scope. The
   assertion was benign outside of asserts builds and would only fire in C.

clang/lib/AST/FormatString.cpp

@@ -351,12 +351,10 @@ ArgType::matchesType(ASTContext &C, QualType argTy) const {
     case AnyCharTy: {
       if (const auto *ETy = argTy->getAs<EnumType>()) {
         // If the enum is incomplete we know nothing about the underlying type.
-        // Assume that it's 'int'. Do not use the underlying type for a scoped
-        // enumeration.
+        // Assume that it's 'int'.
         if (!ETy->getDecl()->isComplete())
           return NoMatch;
-        if (ETy->isUnscopedEnumerationType())
-          argTy = ETy->getDecl()->getIntegerType();
+        argTy = ETy->getDecl()->getIntegerType();
       }
 
       if (const auto *BT = argTy->getAs<BuiltinType>()) {
@@ -393,11 +391,10 @@ ArgType::matchesType(ASTContext &C, QualType argTy) const {
     case SpecificTy: {
       if (const EnumType *ETy = argTy->getAs<EnumType>()) {
         // If the enum is incomplete we know nothing about the underlying type.
-        // Assume that it's 'int'. Do not use the underlying type for a scoped
-        // enumeration as that needs an exact match.
+        // Assume that it's 'int'.
         if (!ETy->getDecl()->isComplete())
           argTy = C.IntTy;
-        else if (ETy->isUnscopedEnumerationType())
+        else
           argTy = ETy->getDecl()->getIntegerType();
       }
       argTy = C.getCanonicalType(argTy).getUnqualifiedType();

clang/lib/Sema/SemaChecking.cpp

@@ -11500,18 +11500,12 @@ CheckPrintfHandler::checkFormatExpr(const analyze_printf::PrintfSpecifier &FS,
       ImplicitMatch == ArgType::NoMatchTypeConfusion)
     Match = ImplicitMatch;
   assert(Match != ArgType::MatchPromotion);
-  // Look through unscoped enums to their underlying type.
+  // Look through enums to their underlying type.
   bool IsEnum = false;
   bool IsScopedEnum = false;
   if (auto EnumTy = ExprTy->getAs<EnumType>()) {
-    if (EnumTy->isUnscopedEnumerationType()) {
-      ExprTy = EnumTy->getDecl()->getIntegerType();
-      // This controls whether we're talking about the underlying type or not,
-      // which we only want to do when it's an unscoped enum.
-      IsEnum = true;
-    } else {
-      IsScopedEnum = true;
-    }
+    ExprTy = EnumTy->getDecl()->getIntegerType();
+    IsEnum = true;
   }
 
   // %C in an Objective-C context prints a unichar, not a wchar_t.

clang/test/SemaCXX/format-strings.cpp

@@ -213,28 +213,4 @@ void f() {
 
 
 }
-
-namespace ScopedEnumerations {
-enum class Scoped1 { One };
-enum class Scoped2 : unsigned short { Two };
-
-void f(Scoped1 S1, Scoped2 S2) {
-  printf("%hhd", S1); // expected-warning {{format specifies type 'char' but the argument has type 'Scoped1'}}
-  printf("%hd", S1);  // expected-warning {{format specifies type 'short' but the argument has type 'Scoped1'}}
-  printf("%d", S1);   // expected-warning {{format specifies type 'int' but the argument has type 'Scoped1'}}
-
-  printf("%hhd", S2); // expected-warning {{format specifies type 'char' but the argument has type 'Scoped2'}}
-  printf("%hd", S2);  // expected-warning {{format specifies type 'short' but the argument has type 'Scoped2'}}
-  printf("%d", S2);   // expected-warning {{format specifies type 'int' but the argument has type 'Scoped2'}}
-
-  scanf("%hhd", &S1); // expected-warning {{format specifies type 'char *' but the argument has type 'Scoped1 *'}}
-  scanf("%hd", &S1);  // expected-warning {{format specifies type 'short *' but the argument has type 'Scoped1 *'}}
-  scanf("%d", &S1);  // expected-warning {{format specifies type 'int *' but the argument has type 'Scoped1 *'}}
-
-  scanf("%hhd", &S2); // expected-warning {{format specifies type 'char *' but the argument has type 'Scoped2 *'}}
-  scanf("%hd", &S2);  // expected-warning {{format specifies type 'short *' but the argument has type 'Scoped2 *'}}
-  scanf("%d", &S2);  // expected-warning {{format specifies type 'int *' but the argument has type 'Scoped2 *'}}
-}
-}
-
 #endif