Rework the printing of attributes (#87281)

Commit 46f3ade introduced a
notion of printing the attributes on the left to improve the printing of
attributes attached to variable declarations. The intent was to produce
more GCC compatible code because clang tends to print the attributes on
the right hand side which is not accepted by gcc.

This approach has increased the complexity in tablegen and the
attrubutes themselves as now the are supposed to know where they could
appear. That lead to mishandling of the `override` keyword which is
modelled as an attribute in clang.

This patch takes an inspiration from the existing approach and tries to
keep the position of the attributes as they were written. To do so we
use simpler heuristic which checks if the source locations of the
attribute precedes the declaration. If so, it is considered to be
printed before the declaration.

Fixes #87151

Author: vgvassilev

clang/include/clang/Basic/Attr.td

@@ -324,13 +324,10 @@ class Spelling<string name, string variety, int version = 1> {
 }
 
 class GNU<string name> : Spelling<name, "GNU">;
-class Declspec<string name> : Spelling<name, "Declspec"> {
-  bit PrintOnLeft = 1;
-}
+class Declspec<string name> : Spelling<name, "Declspec">;
 class Microsoft<string name> : Spelling<name, "Microsoft">;
 class CXX11<string namespace, string name, int version = 1>
     : Spelling<name, "CXX11", version> {
-  bit CanPrintOnLeft = 0;
   string Namespace = namespace;
 }
 class C23<string namespace, string name, int version = 1>
@@ -596,12 +593,6 @@ class AttrSubjectMatcherAggregateRule<AttrSubject subject> {
 def SubjectMatcherForNamed : AttrSubjectMatcherAggregateRule<Named>;
 
 class Attr {
-  // Specifies that when printed, this attribute is meaningful on the
-  // 'left side' of the declaration.
-  bit CanPrintOnLeft = 1;
-  // Specifies that when printed, this attribute is required to be printed on
-  // the 'left side' of the declaration.
-  bit PrintOnLeft = 0;
   // The various ways in which an attribute can be spelled in source
   list<Spelling> Spellings;
   // The things to which an attribute can appertain
@@ -937,7 +928,6 @@ def AVRSignal : InheritableAttr, TargetSpecificAttr<TargetAVR> {
 }
 
 def AsmLabel : InheritableAttr {
-  let CanPrintOnLeft = 0;
   let Spellings = [CustomKeyword<"asm">, CustomKeyword<"__asm__">];
   let Args = [
     // Label specifies the mangled name for the decl.
@@ -1534,7 +1524,6 @@ def AllocSize : InheritableAttr {
 }
 
 def EnableIf : InheritableAttr {
-  let CanPrintOnLeft = 0;
   // Does not have a [[]] spelling because this attribute requires the ability
   // to parse function arguments but the attribute is not written in the type
   // position.
@@ -3171,7 +3160,6 @@ def Unavailable : InheritableAttr {
 }
 
 def DiagnoseIf : InheritableAttr {
-  let CanPrintOnLeft = 0;
   // Does not have a [[]] spelling because this attribute requires the ability
   // to parse function arguments but the attribute is not written in the type
   // position.

clang/include/clang/Basic/CMakeLists.txt

@@ -31,16 +31,6 @@ clang_tablegen(AttrList.inc -gen-clang-attr-list
   SOURCE Attr.td
   TARGET ClangAttrList)
 
-clang_tablegen(AttrLeftSideCanPrintList.inc -gen-clang-attr-can-print-left-list
-  -I ${CMAKE_CURRENT_SOURCE_DIR}/../../
-  SOURCE Attr.td
-  TARGET ClangAttrCanPrintLeftList)
-
-clang_tablegen(AttrLeftSideMustPrintList.inc -gen-clang-attr-must-print-left-list
-  -I ${CMAKE_CURRENT_SOURCE_DIR}/../../
-  SOURCE Attr.td
-  TARGET ClangAttrMustPrintLeftList)
-
 clang_tablegen(AttrSubMatchRulesList.inc -gen-clang-attr-subject-match-rule-list
   -I ${CMAKE_CURRENT_SOURCE_DIR}/../../
   SOURCE Attr.td

clang/lib/AST/DeclPrinter.cpp

@@ -21,6 +21,7 @@
 #include "clang/AST/ExprCXX.h"
 #include "clang/AST/PrettyPrinter.h"
 #include "clang/Basic/Module.h"
+#include "clang/Basic/SourceManager.h"
 #include "llvm/Support/raw_ostream.h"
 using namespace clang;
 
@@ -49,18 +50,6 @@ namespace {
 
     void PrintObjCTypeParams(ObjCTypeParamList *Params);
 
-    enum class AttrPrintLoc {
-      None = 0,
-      Left = 1,
-      Right = 2,
-      Any = Left | Right,
-
-      LLVM_MARK_AS_BITMASK_ENUM(/*DefaultValue=*/Any)
-    };
-
-    void prettyPrintAttributes(Decl *D, raw_ostream &out,
-                               AttrPrintLoc loc = AttrPrintLoc::Any);
-
   public:
     DeclPrinter(raw_ostream &Out, const PrintingPolicy &Policy,
                 const ASTContext &Context, unsigned Indentation = 0,
@@ -129,11 +118,10 @@ namespace {
                                 const TemplateParameterList *Params);
     void printTemplateArguments(llvm::ArrayRef<TemplateArgumentLoc> Args,
                                 const TemplateParameterList *Params);
-
-    inline void prettyPrintAttributes(Decl *D) {
-      prettyPrintAttributes(D, Out);
-    }
-
+    enum class AttrPosAsWritten { Unknown = 0, Default, Left, Right };
+    void
+    prettyPrintAttributes(const Decl *D,
+                          AttrPosAsWritten Pos = AttrPosAsWritten::Default);
     void prettyPrintPragmas(Decl *D);
     void printDeclType(QualType T, StringRef DeclName, bool Pack = false);
   };
@@ -250,87 +238,53 @@ raw_ostream& DeclPrinter::Indent(unsigned Indentation) {
   return Out;
 }
 
-// For CLANG_ATTR_LIST_CanPrintOnLeft macro.
-#include "clang/Basic/AttrLeftSideCanPrintList.inc"
+static DeclPrinter::AttrPosAsWritten getPosAsWritten(const Attr *A,
+                                                     const Decl *D) {
+  SourceLocation ALoc = A->getLoc();
+  SourceLocation DLoc = D->getLocation();
+  const ASTContext &C = D->getASTContext();
+  if (ALoc.isInvalid() || DLoc.isInvalid())
+    return DeclPrinter::AttrPosAsWritten::Unknown;
 
-// For CLANG_ATTR_LIST_PrintOnLeft macro.
-#include "clang/Basic/AttrLeftSideMustPrintList.inc"
+  if (C.getSourceManager().isBeforeInTranslationUnit(ALoc, DLoc))
+    return DeclPrinter::AttrPosAsWritten::Left;
 
-static bool canPrintOnLeftSide(attr::Kind kind) {
-#ifdef CLANG_ATTR_LIST_CanPrintOnLeft
-  switch (kind) {
-  CLANG_ATTR_LIST_CanPrintOnLeft
-    return true;
-  default:
-    return false;
-  }
-#else
-  return false;
-#endif
-}
-
-static bool canPrintOnLeftSide(const Attr *A) {
-  if (A->isStandardAttributeSyntax())
-    return false;
-
-  return canPrintOnLeftSide(A->getKind());
+  return DeclPrinter::AttrPosAsWritten::Right;
 }
 
-static bool mustPrintOnLeftSide(attr::Kind kind) {
-#ifdef CLANG_ATTR_LIST_PrintOnLeft
-  switch (kind) {
-  CLANG_ATTR_LIST_PrintOnLeft
-    return true;
-  default:
-    return false;
-  }
-#else
-  return false;
-#endif
-}
-
-static bool mustPrintOnLeftSide(const Attr *A) {
-  if (A->isDeclspecAttribute())
-    return true;
-
-  return mustPrintOnLeftSide(A->getKind());
-}
-
-void DeclPrinter::prettyPrintAttributes(Decl *D, llvm::raw_ostream &Out,
-                                        AttrPrintLoc Loc) {
+void DeclPrinter::prettyPrintAttributes(const Decl *D,
+                                        AttrPosAsWritten Pos /*=Default*/) {
   if (Policy.PolishForDeclaration)
     return;
 
   if (D->hasAttrs()) {
-    AttrVec &Attrs = D->getAttrs();
+    assert(Pos != AttrPosAsWritten::Unknown && "Use Default");
+    const AttrVec &Attrs = D->getAttrs();
     for (auto *A : Attrs) {
       if (A->isInherited() || A->isImplicit())
         continue;
-
-      AttrPrintLoc AttrLoc = AttrPrintLoc::Right;
-      if (mustPrintOnLeftSide(A)) {
-        // If we must always print on left side (e.g. declspec), then mark as
-        // so.
-        AttrLoc = AttrPrintLoc::Left;
-      } else if (canPrintOnLeftSide(A)) {
-        // For functions with body defined we print the attributes on the left
-        // side so that GCC accept our dumps as well.
-        if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D);
-            FD && FD->isThisDeclarationADefinition())
-          // In case Decl is a function with a body, then attrs should be print
-          // on the left side.
-          AttrLoc = AttrPrintLoc::Left;
-
-          // In case it is a variable declaration with a ctor, then allow
-          // printing on the left side for readbility.
-        else if (const VarDecl *VD = dyn_cast<VarDecl>(D);
-                   VD && VD->getInit() &&
-                   VD->getInitStyle() == VarDecl::CallInit)
-          AttrLoc = AttrPrintLoc::Left;
+      switch (A->getKind()) {
+#define ATTR(X)
+#define PRAGMA_SPELLING_ATTR(X) case attr::X:
+#include "clang/Basic/AttrList.inc"
+        break;
+      default:
+        AttrPosAsWritten APos = getPosAsWritten(A, D);
+        // Might trigger on programatically created attributes or declarations
+        // with no source locations.
+        assert(APos != AttrPosAsWritten::Unknown &&
+               "Invalid source location for attribute or decl.");
+        assert(APos != AttrPosAsWritten::Default &&
+               "Default not a valid for an attribute location");
+        if (Pos == AttrPosAsWritten::Default || Pos == APos) {
+          if (Pos != AttrPosAsWritten::Left)
+            Out << ' ';
+          A->printPretty(Out, Policy);
+          if (Pos == AttrPosAsWritten::Left)
+            Out << ' ';
+        }
+        break;
       }
-      // Only print the side matches the user requested.
-      if ((Loc & AttrLoc) != AttrPrintLoc::None)
-        A->printPretty(Out, Policy);
     }
   }
 }
@@ -691,8 +645,10 @@ static void MaybePrintTagKeywordIfSupressingScopes(PrintingPolicy &Policy,
 
 void DeclPrinter::VisitFunctionDecl(FunctionDecl *D) {
   if (!D->getDescribedFunctionTemplate() &&
-      !D->isFunctionTemplateSpecialization())
+      !D->isFunctionTemplateSpecialization()) {
     prettyPrintPragmas(D);
+    prettyPrintAttributes(D, AttrPosAsWritten::Left);
+  }
 
   if (D->isFunctionTemplateSpecialization())
     Out << "template<> ";
@@ -702,22 +658,6 @@ void DeclPrinter::VisitFunctionDecl(FunctionDecl *D) {
       printTemplateParameters(D->getTemplateParameterList(I));
   }
 
-  std::string LeftsideAttrs;
-  llvm::raw_string_ostream LSAS(LeftsideAttrs);
-
-  prettyPrintAttributes(D, LSAS, AttrPrintLoc::Left);
-
-  // prettyPrintAttributes print a space on left side of the attribute.
-  if (LeftsideAttrs[0] == ' ') {
-    // Skip the space prettyPrintAttributes generated.
-    LeftsideAttrs.erase(0, LeftsideAttrs.find_first_not_of(' '));
-
-    // Add a single space between the attribute and the Decl name.
-    LSAS << ' ';
-  }
-
-  Out << LeftsideAttrs;
-
   CXXConstructorDecl *CDecl = dyn_cast<CXXConstructorDecl>(D);
   CXXConversionDecl *ConversionDecl = dyn_cast<CXXConversionDecl>(D);
   CXXDeductionGuideDecl *GuideDecl = dyn_cast<CXXDeductionGuideDecl>(D);
@@ -883,7 +823,7 @@ void DeclPrinter::VisitFunctionDecl(FunctionDecl *D) {
     Ty.print(Out, Policy, Proto);
   }
 
-  prettyPrintAttributes(D, Out, AttrPrintLoc::Right);
+  prettyPrintAttributes(D, AttrPosAsWritten::Right);
 
   if (D->isPureVirtual())
     Out << " = 0";
@@ -976,27 +916,12 @@ void DeclPrinter::VisitLabelDecl(LabelDecl *D) {
 void DeclPrinter::VisitVarDecl(VarDecl *D) {
   prettyPrintPragmas(D);
 
+  prettyPrintAttributes(D, AttrPosAsWritten::Left);
+
   if (const auto *Param = dyn_cast<ParmVarDecl>(D);
       Param && Param->isExplicitObjectParameter())
     Out << "this ";
 
-  std::string LeftSide;
-  llvm::raw_string_ostream LeftSideStream(LeftSide);
-
-  // Print attributes that should be placed on the left, such as __declspec.
-  prettyPrintAttributes(D, LeftSideStream, AttrPrintLoc::Left);
-
-  // prettyPrintAttributes print a space on left side of the attribute.
-  if (LeftSide[0] == ' ') {
-    // Skip the space prettyPrintAttributes generated.
-    LeftSide.erase(0, LeftSide.find_first_not_of(' '));
-
-    // Add a single space between the attribute and the Decl name.
-    LeftSideStream << ' ';
-  }
-
-  Out << LeftSide;
-
   QualType T = D->getTypeSourceInfo()
     ? D->getTypeSourceInfo()->getType()
     : D->getASTContext().getUnqualifiedObjCPointerType(D->getType());
@@ -1029,21 +954,16 @@ void DeclPrinter::VisitVarDecl(VarDecl *D) {
     }
   }
 
-  StringRef Name;
-
-  Name = (isa<ParmVarDecl>(D) && Policy.CleanUglifiedParameters &&
-          D->getIdentifier())
-             ? D->getIdentifier()->deuglifiedName()
-             : D->getName();
-
   if (!Policy.SuppressTagKeyword && Policy.SuppressScope &&
       !Policy.SuppressUnwrittenScope)
     MaybePrintTagKeywordIfSupressingScopes(Policy, T, Out);
-  printDeclType(T, Name);
 
-  // Print the attributes that should be placed right before the end of the
-  // decl.
-  prettyPrintAttributes(D, Out, AttrPrintLoc::Right);
+  printDeclType(T, (isa<ParmVarDecl>(D) && Policy.CleanUglifiedParameters &&
+                    D->getIdentifier())
+                       ? D->getIdentifier()->deuglifiedName()
+                       : D->getName());
+
+  prettyPrintAttributes(D, AttrPosAsWritten::Right);
 
   Expr *Init = D->getInit();
   if (!Policy.SuppressInitializers && Init) {

clang/lib/AST/StmtPrinter.cpp

@@ -292,8 +292,11 @@ void StmtPrinter::VisitLabelStmt(LabelStmt *Node) {
 }
 
 void StmtPrinter::VisitAttributedStmt(AttributedStmt *Node) {
-  for (const auto *Attr : Node->getAttrs()) {
+  llvm::ArrayRef<const Attr *> Attrs = Node->getAttrs();
+  for (const auto *Attr : Attrs) {
     Attr->printPretty(OS, Policy);
+    if (Attr != Attrs.back())
+      OS << ' ';
   }
 
   PrintStmt(Node->getSubStmt(), 0);

clang/test/AST/ast-print-method-decl.cpp

@@ -94,7 +94,7 @@ struct DefMethodsWithoutBody {
   // CHECK-NEXT: DefMethodsWithoutBody() = default;
   ~DefMethodsWithoutBody() = default;
 
-  // CHECK-NEXT: __attribute__((alias("X"))) void m1();
+  // CHECK-NEXT: void m1() __attribute__((alias("X")));
   void m1() __attribute__((alias("X")));
 
   // CHECK-NEXT: };

clang/test/AST/ast-print-no-sanitize.cpp

@@ -4,4 +4,4 @@ void should_not_crash_1() __attribute__((no_sanitize_memory));
 [[clang::no_sanitize_memory]] void should_not_crash_2();
 
 // CHECK: void should_not_crash_1() __attribute__((no_sanitize("memory")));
-// CHECK: void should_not_crash_2() {{\[\[}}clang::no_sanitize("memory"){{\]\]}};
+// CHECK: {{\[\[}}clang::no_sanitize("memory"){{\]\]}} void should_not_crash_2();

clang/test/AST/attr-print-emit.cpp

@@ -73,3 +73,18 @@ class C {
   // CHECK: void pwtt(void *, int) __attribute__((pointer_with_type_tag(foo, 2, 3)));
   void pwtt(void *, int) __attribute__((pointer_with_type_tag(foo, 2, 3)));
 };
+
+#define ANNOTATE_ATTR __attribute__((annotate("Annotated")))
+ANNOTATE_ATTR int annotated_attr ANNOTATE_ATTR = 0;
+// CHECK: __attribute__((annotate("Annotated"))) int annotated_attr __attribute__((annotate("Annotated"))) = 0;
+
+// FIXME: We do not print the attribute as written after the type specifier.
+int ANNOTATE_ATTR annotated_attr_fixme = 0;
+// CHECK: __attribute__((annotate("Annotated"))) int annotated_attr_fixme = 0;
+
+#define NONNULL_ATTR  __attribute__((nonnull(1)))
+ANNOTATE_ATTR NONNULL_ATTR void fn_non_null_annotated_attr(int *) __attribute__((annotate("AnnotatedRHS")));
+// CHECK:__attribute__((annotate("Annotated"))) __attribute__((nonnull(1))) void fn_non_null_annotated_attr(int *) __attribute__((annotate("AnnotatedRHS")));
+
+[[gnu::nonnull(1)]] [[gnu::always_inline]] void cxx11_attr(int*) ANNOTATE_ATTR;
+// CHECK: {{\[\[}}gnu::nonnull(1)]] {{\[\[}}gnu::always_inline]] void cxx11_attr(int *) __attribute__((annotate("Annotated")));

clang/test/Analysis/scopes-cfg-output.cpp

@@ -1469,7 +1469,7 @@ void test_cleanup_functions2(int m) {
 // CHECK:       [B1]
 // CHECK-NEXT:    1: CFGScopeBegin(f)
 // CHECK-NEXT:    2:  (CXXConstructExpr, [B1.3], F)
-// CHECK-NEXT:    3: __attribute__((cleanup(cleanup_F))) F f;
+// CHECK-NEXT:    3: F f __attribute__((cleanup(cleanup_F)));
 // CHECK-NEXT:    4: CleanupFunction (cleanup_F)
 // CHECK-NEXT:    5: [B1.3].~F() (Implicit destructor)
 // CHECK-NEXT:    6: CFGScopeEnd(f)