From d466ea1b0873ce07700f5a0c48709da2edf227ff Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Tue, 30 Jun 2009 06:24:05 +0000
Subject: [PATCH] Implement PR4175, catching some questionable comparisons. 
 Patch by David Majnemer!

llvm-svn: 74513
---
 .../clang/Basic/DiagnosticSemaKinds.td        |  4 ++++
 clang/lib/Sema/SemaExpr.cpp                   | 21 +++++++++++++++++--
 clang/test/Sema/compare.c                     | 14 +++++++++++++
 3 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 652f7430f0c6..8a532d62a71e 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1213,6 +1213,10 @@ def err_typecheck_sub_ptr_object : Error<
   "subtraction of pointer %0 requires pointee to be a complete object type">;
 def err_typecheck_sub_ptr_compatible : Error<
   "%0 and %1 are not pointers to compatible types">;
+def ext_typecheck_ordered_comparison_of_pointer_integer : ExtWarn<
+  "ordered comparison between pointer and integer (%0 and %1)">;
+def ext_typecheck_ordered_comparison_of_function_pointers : ExtWarn<
+  "ordered comparison of function pointers (%0 and %1)">;
 def ext_typecheck_comparison_of_pointer_integer : ExtWarn<
   "comparison between pointer and integer (%0 and %1)">;
 def ext_typecheck_comparison_of_distinct_pointers : ExtWarn<
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 28617bbfeac5..1df3d4f722f6 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -4028,6 +4028,17 @@ QualType Sema::CheckCompareOperands(Expr *&lex, Expr *&rex, SourceLocation Loc,
     QualType RCanPointeeTy =
       Context.getCanonicalType(rType->getAsPointerType()->getPointeeType());
 
+    if (rType->isFunctionPointerType() || lType->isFunctionPointerType()) {
+      if (isRelational) {
+        Diag(Loc, diag::ext_typecheck_ordered_comparison_of_function_pointers)
+          << lType << rType << lex->getSourceRange() << rex->getSourceRange();
+      }
+    }
+    if (((!LHSIsNull || isRelational) && LCanPointeeTy->isVoidType()) !=
+        ((!RHSIsNull || isRelational) && RCanPointeeTy->isVoidType())) {
+      Diag(Loc, diag::ext_typecheck_comparison_of_distinct_pointers)
+        << lType << rType << lex->getSourceRange() << rex->getSourceRange();
+    }
     // Simple check: if the pointee types are identical, we're done.
     if (LCanPointeeTy == RCanPointeeTy)
       return ResultTy;
@@ -4140,7 +4151,10 @@ QualType Sema::CheckCompareOperands(Expr *&lex, Expr *&rex, SourceLocation Loc,
   }
   if ((lType->isPointerType() || lType->isObjCQualifiedIdType()) &&
        rType->isIntegerType()) {
-    if (!RHSIsNull)
+    if (isRelational)
+      Diag(Loc, diag::ext_typecheck_ordered_comparison_of_pointer_integer)
+        << lType << rType << lex->getSourceRange() << rex->getSourceRange();
+    else if (!RHSIsNull)
       Diag(Loc, diag::ext_typecheck_comparison_of_pointer_integer)
         << lType << rType << lex->getSourceRange() << rex->getSourceRange();
     ImpCastExprToType(rex, lType); // promote the integer to pointer
@@ -4148,7 +4162,10 @@ QualType Sema::CheckCompareOperands(Expr *&lex, Expr *&rex, SourceLocation Loc,
   }
   if (lType->isIntegerType() &&
       (rType->isPointerType() || rType->isObjCQualifiedIdType())) {
-    if (!LHSIsNull)
+    if (isRelational)
+      Diag(Loc, diag::ext_typecheck_ordered_comparison_of_pointer_integer)
+        << lType << rType << lex->getSourceRange() << rex->getSourceRange();
+    else if (!LHSIsNull)
       Diag(Loc, diag::ext_typecheck_comparison_of_pointer_integer)
         << lType << rType << lex->getSourceRange() << rex->getSourceRange();
     ImpCastExprToType(lex, rType); // promote the integer to pointer
diff --git a/clang/test/Sema/compare.c b/clang/test/Sema/compare.c
index 4b44bf5b96a0..51f77317385c 100644
--- a/clang/test/Sema/compare.c
+++ b/clang/test/Sema/compare.c
@@ -15,3 +15,17 @@ int arrays(char (*a)[5], char(*b)[10], char(*c)[5]) {
   int d = (a == c);
   return a == b; // expected-warning {{comparison of distinct pointer types}}
 }
+
+int pointers(int *a)
+{
+  return a > 0; // expected-warning {{ordered comparison between pointer and integer}}
+  return a > (void *)0; // expected-warning {{comparison of distinct pointer types}}
+}
+
+int function_pointers(int (*a)(int), int (*b)(int))
+{
+  return a > b; // expected-warning {{ordered comparison of function pointers}}
+  return function_pointers > function_pointers; // expected-warning {{ordered comparison of function pointers}}
+  return a == (void *) 0;
+  return a == (void *) 1; // expected-warning {{comparison of distinct pointer types}}
+}