[clang-tools-extra] [clang] [llvm] [clang] support Wold-style-declaration (PR #78837)

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SihangZhu wrote:

ping

https://github.com/llvm/llvm-project/pull/78837
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[clang-tools-extra] [clang] [llvm] [clang] support Wold-style-declaration (PR #78837)

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https://github.com/SihangZhu updated 
https://github.com/llvm/llvm-project/pull/78837

>From 773b14c803b69073ef6a073b14b68fe8e5b628c3 Mon Sep 17 00:00:00 2001
From: SihangZhu 
Date: Sat, 20 Jan 2024 17:11:31 +0800
Subject: [PATCH] [clang] support Wold-style-declaration as gcc

---
 .../clang/Basic/DiagnosticCommonKinds.td  |  2 ++
 clang/include/clang/Basic/DiagnosticGroups.td |  2 ++
 clang/lib/Parse/ParseDecl.cpp | 11 +++
 clang/test/Parser/old-style-declaration.c | 33 +++
 4 files changed, 48 insertions(+)
 create mode 100644 clang/test/Parser/old-style-declaration.c

diff --git a/clang/include/clang/Basic/DiagnosticCommonKinds.td 
b/clang/include/clang/Basic/DiagnosticCommonKinds.td
index 5544dc88004d9a3..0d29316767e9508 100644
--- a/clang/include/clang/Basic/DiagnosticCommonKinds.td
+++ b/clang/include/clang/Basic/DiagnosticCommonKinds.td
@@ -84,6 +84,8 @@ def err_param_redefinition : Error<"redefinition of parameter 
%0">;
 def warn_method_param_redefinition : Warning<"redefinition of method parameter 
%0">;
 def warn_method_param_declaration : Warning<"redeclaration of method parameter 
%0">,
   InGroup, DefaultIgnore;
+def warn_old_style_declaration: Warning <"'%0' is not at beginning of 
declaration">,
+  InGroup, DefaultIgnore;
 def err_invalid_storage_class_in_func_decl : Error<
   "invalid storage class specifier in function declarator">;
 def err_expected_namespace_name : Error<"expected namespace name">;
diff --git a/clang/include/clang/Basic/DiagnosticGroups.td 
b/clang/include/clang/Basic/DiagnosticGroups.td
index 6765721ae7002c1..ebe751a99479711 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -578,6 +578,7 @@ def ObjCPointerIntrospect : 
DiagGroup<"deprecated-objc-pointer-introspection", [
 def ObjCMultipleMethodNames : DiagGroup<"objc-multiple-method-names">;
 def ObjCFlexibleArray : DiagGroup<"objc-flexible-array">;
 def ObjCBoxing : DiagGroup<"objc-boxing">;
+def OldStyleDeclaration : DiagGroup<"old-style-declaration">;
 def CompletionHandler : DiagGroup<"completion-handler">;
 def CalledOnceParameter : DiagGroup<"called-once-parameter", 
[CompletionHandler]>;
 def OpenCLUnsupportedRGBA: DiagGroup<"opencl-unsupported-rgba">;
@@ -1026,6 +1027,7 @@ def Extra : DiagGroup<"extra", [
 EmptyInitStatement,
 StringConcatation,
 FUseLdPath,
+OldStyleDeclaration,
   ]>;
 
 def Most : DiagGroup<"most", [
diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index 356e7851ec639c1..ab1555ebc190888 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -3348,6 +3348,7 @@ void Parser::ParseDeclarationSpecifiers(
   while (true) {
 bool isInvalid = false;
 bool isStorageClass = false;
+bool isFunctionSpecifier = false;
 const char *PrevSpec = nullptr;
 unsigned DiagID = 0;
 
@@ -4092,6 +4093,7 @@ void Parser::ParseDeclarationSpecifiers(
 // function-specifier
 case tok::kw_inline:
   isInvalid = DS.setFunctionSpecInline(Loc, PrevSpec, DiagID);
+  isFunctionSpecifier = true;
   break;
 case tok::kw_virtual:
   // C++ for OpenCL does not allow virtual function qualifier, to avoid
@@ -4104,6 +4106,7 @@ void Parser::ParseDeclarationSpecifiers(
 isInvalid = true;
   } else {
 isInvalid = DS.setFunctionSpecVirtual(Loc, PrevSpec, DiagID);
+isFunctionSpecifier = true;
   }
   break;
 case tok::kw_explicit: {
@@ -4140,12 +4143,14 @@ void Parser::ParseDeclarationSpecifiers(
   }
   isInvalid = DS.setFunctionSpecExplicit(ExplicitLoc, PrevSpec, DiagID,
  ExplicitSpec, CloseParenLoc);
+  isFunctionSpecifier = true;
   break;
 }
 case tok::kw__Noreturn:
   if (!getLangOpts().C11)
 Diag(Tok, diag::ext_c11_feature) << Tok.getName();
   isInvalid = DS.setFunctionSpecNoreturn(Loc, PrevSpec, DiagID);
+  isFunctionSpecifier = true;
   break;
 
 // alignment-specifier
@@ -4552,6 +4557,12 @@ void Parser::ParseDeclarationSpecifiers(
   continue;
 }
 
+unsigned Specs = DS.getParsedSpecifiers();
+if (!getLangOpts().CPlusPlus && (isFunctionSpecifier || isStorageClass)) {
+  if (Specs & DeclSpec::PQ_TypeQualifier || DS.hasTypeSpecifier())
+Diag(Tok, diag::warn_old_style_declaration) << Tok.getName();
+}
+
 DS.SetRangeEnd(ConsumedEnd.isValid() ? ConsumedEnd : Tok.getLocation());
 
 // If the specifier wasn't legal, issue a diagnostic.
diff --git a/clang/test/Parser/old-style-declaration.c 
b/clang/test/Parser/old-style-declaration.c
new file mode 100644
index 000..e7ccea32bfa9571
--- /dev/null
+++ b/clang/test/Parser/old-style-declaration.c
@@ -0,0 +1,33 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -Wold-style-declaration %s
+// RUN: %clang_cc1 -fsyntax-only -verify -Wextra %s
+
+static int x0;
+int __attribute__ ((aligned