From a798ebc82627ea9cb7a00da07d2b60f9f2114f69 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Sat, 5 Apr 2008 05:52:15 +0000
Subject: [PATCH] Step #1 to fixing PR2012: c89 allows declspecs to be
 completely missing from function definitions only.  If we see a function
 definiton with missing declspecs, just fudge in an int.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@49250 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/clang/Basic/LangOptions.h |  2 ++
 lib/Parse/Parser.cpp              | 21 +++++++++++++++++----
 test/Sema/c89.c                   |  6 ++++++
 3 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/include/clang/Basic/LangOptions.h b/include/clang/Basic/LangOptions.h
index bee0b51ab2..947492f04f 100644
--- a/include/clang/Basic/LangOptions.h
+++ b/include/clang/Basic/LangOptions.h
@@ -49,6 +49,8 @@ struct LangOptions {
     LaxVectorConversions = 0;
   }
   
+  bool isC90() const { return !C99 && !CPlusPlus; }
+  
   /// Emit - Emit this LangOptions object to bitcode.
   void Emit(llvm::Serializer& S) const;
   
diff --git a/lib/Parse/Parser.cpp b/lib/Parse/Parser.cpp
index 703144b3c4..76091245b5 100644
--- a/lib/Parse/Parser.cpp
+++ b/lib/Parse/Parser.cpp
@@ -356,8 +356,10 @@ Parser::DeclTy *Parser::ParseExternalDeclaration() {
 /// compound-statement in function-definition.
 ///
 ///       function-definition: [C99 6.9.1]
-///         declaration-specifiers[opt] declarator declaration-list[opt] 
-///                 compound-statement
+///         decl-specs      declarator declaration-list[opt] compound-statement
+/// [C90] function-definition: [C99 6.7.1] - implicit int result
+/// [C90]   decl-specs[opt] declarator declaration-list[opt] compound-statement 
+///
 ///       declaration: [C99 6.7]
 ///         declaration-specifiers init-declarator-list[opt] ';'
 /// [!C99]  init-declarator-list ';'                   [TODO: warn in c99 mode]
@@ -451,8 +453,10 @@ Parser::DeclTy *Parser::ParseDeclarationOrFunctionDefinition() {
 /// Declarator is well formed.  If this is a K&R-style function, read the
 /// parameters declaration-list, then start the compound-statement.
 ///
-///         declaration-specifiers[opt] declarator declaration-list[opt] 
-///                 compound-statement                           [TODO]
+///       function-definition: [C99 6.9.1]
+///         decl-specs      declarator declaration-list[opt] compound-statement
+/// [C90] function-definition: [C99 6.7.1] - implicit int result
+/// [C90]   decl-specs[opt] declarator declaration-list[opt] compound-statement 
 ///
 Parser::DeclTy *Parser::ParseFunctionDefinition(Declarator &D) {
   const DeclaratorChunk &FnTypeInfo = D.getTypeObject(0);
@@ -460,6 +464,15 @@ Parser::DeclTy *Parser::ParseFunctionDefinition(Declarator &D) {
          "This isn't a function declarator!");
   const DeclaratorChunk::FunctionTypeInfo &FTI = FnTypeInfo.Fun;
   
+  // If this is C90 and the declspecs were completely missing, fudge in an
+  // implicit int.  We do this here because this is the only place where
+  // declaration-specifiers are completely optional in the grammar.
+  if (getLang().isC90() && !D.getDeclSpec().getParsedSpecifiers() == 0) {
+    const char *PrevSpec;
+    D.getDeclSpec().SetTypeSpecType(DeclSpec::TST_int, D.getIdentifierLoc(),
+                                    PrevSpec);
+  }
+  
   // If this declaration was formed with a K&R-style identifier list for the
   // arguments, parse declarations for all of the args next.
   // int foo(a,b) int a; float b; {}
diff --git a/test/Sema/c89.c b/test/Sema/c89.c
index 831c1ce7c5..301ec374db 100644
--- a/test/Sema/c89.c
+++ b/test/Sema/c89.c
@@ -33,3 +33,9 @@ void test5(register);
 /* PR2041 */
 int *restrict;
 int *__restrict;  /* expected-error {{expected identifier}} */
+
+
+/* Implicit int, always ok */
+foo() {}
+
+
-- 
2.40.0