From be4a5ccb93f013cb7d20ded95b57d115b93130a7 Mon Sep 17 00:00:00 2001
From: Alp Toker <alp@nuanti.com>
Date: Sun, 5 Jan 2014 03:27:57 +0000
Subject: [PATCH] Fix bungled parse recovery in K&R function declarations

  void knrNoSemi(i) int i { }

Adherents of The C Programming Language unfortunate enough to miss a semicolon
as above would be met with a cascade of errors spanning the remainder of the
TU.

This patch introduces a beautiful parse error recovery, complete with helpful
FixIt to restore sanity.

Before (output redacted for brevity):

  error: 'error' diagnostics seen but not expected:
    File declarators.c Line 119: declaration does not declare a parameter
    File declarators.c Line 123: declaration does not declare a parameter
    File declarators.c Line 127: parameter named 'func_E12' is missing
    File declarators.c Line 127: expected ';' at end of declaration
    File declarators.c Line 133: parameter named 'func_E13' is missing
    File declarators.c Line 133: expected ';' at end of declaration
    File declarators.c Line 139: parameter named 'func_E14' is missing
    File declarators.c Line 139: expected ';' at end of declaration
    File declarators.c Line 145: parameter named 'func_E15' is missing
    File declarators.c Line 145: expected ';' at end of declaration
    File declarators.c Line 150: expected function body after function declarator
    File declarators.c Line 119: declaration of 'enum E11' will not be visible outside of this function
    File declarators.c Line 123: declaration of 'enum E12' will not be visible outside of this function
    File declarators.c Line 133: ISO C forbids forward references to 'enum' types
    File declarators.c Line 133: declaration of 'enum E13' will not be visible outside of this function
    File declarators.c Line 139: ISO C forbids forward references to 'enum' types
    File declarators.c Line 139: declaration of 'enum E14' will not be visible outside of this function
    File declarators.c Line 145: ISO C forbids forward references to 'enum' types
    File declarators.c Line 145: declaration of 'enum E15' will not be visible outside of this function
    ...

After:

  declarators.c:103:24: error: expected ';' at end of declaration
  void knrNoSemi(i) int i { }
                         ^
                         ;

Patch found in a sealed envelope dated 1978 with the message "Do not open until
January 2014"

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@198540 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Parse/Parser.cpp      | 9 +++------
 test/Parser/declarators.c | 1 +
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/lib/Parse/Parser.cpp b/lib/Parse/Parser.cpp
index 1c20a47f17..f668c5a8bd 100644
--- a/lib/Parse/Parser.cpp
+++ b/lib/Parse/Parser.cpp
@@ -1285,12 +1285,9 @@ void Parser::ParseKNRParamDeclarations(Declarator &D) {
       ParseDeclarator(ParmDeclarator);
     }
 
-    if (ExpectAndConsumeSemi(diag::err_expected_semi_declaration)) {
-      // Skip to end of block or statement
-      SkipUntil(tok::semi);
-      if (Tok.is(tok::semi))
-        ConsumeToken();
-    }
+    // Consume ';' or recover by skipping to the mandatory function body.
+    if (ExpectAndConsumeSemi(diag::err_expected_semi_declaration))
+      SkipUntil(tok::l_brace, StopBeforeMatch);
   }
 
   // The actions module must verify that all arguments were declared.
diff --git a/test/Parser/declarators.c b/test/Parser/declarators.c
index f77c2d2192..39d9dc9449 100644
--- a/test/Parser/declarators.c
+++ b/test/Parser/declarators.c
@@ -100,6 +100,7 @@ long struct X { int x; } test15(); // expected-error {{'long struct' is invalid}
 
 void test16(i) int i j; { } // expected-error {{expected ';' at end of declaration}}
 void test17(i, j) int i, j k; { } // expected-error {{expected ';' at end of declaration}}
+void knrNoSemi(i) int i { } // expected-error {{expected ';' at end of declaration}}
 
 
 // PR12595
-- 
2.40.0