[PATCH] D17034: Add an AST matcher for null pointers

[Aaron Ballman via cfe-commits]

aaron.ballman updated this revision to Diff 48075.
aaron.ballman added a comment.

Using the AST_MATCHER_FUNCTION macro instead.

Using Expr::isNullPointerConstant() turns out to have strange behavior with implicit casts and nullptr, and also requires further restrictions (for instance, it claims the initializer for `int i = 0` is a null pointer constant, which is strictly true, but practically useless).


http://reviews.llvm.org/D17034

Files:
  docs/LibASTMatchersReference.html
  include/clang/ASTMatchers/ASTMatchers.h
  lib/ASTMatchers/Dynamic/Registry.cpp
  unittests/ASTMatchers/ASTMatchersTest.cpp

Index: unittests/ASTMatchers/ASTMatchersTest.cpp
===================================================================
--- unittests/ASTMatchers/ASTMatchersTest.cpp
+++ unittests/ASTMatchers/ASTMatchersTest.cpp
@@ -5348,5 +5348,15 @@
                       )));
 }
 
+TEST(NullPointerConstants, Basic) {
+  EXPECT_TRUE(matches("#define NULL ((void *)0)\n"
+                      "void *v1 = NULL;", expr(nullPointerConstant())));
+  EXPECT_TRUE(matches("void *v2 = nullptr;", expr(nullPointerConstant())));
+  EXPECT_TRUE(matches("void *v3 = __null;", expr(nullPointerConstant())));
+  EXPECT_TRUE(matches("char *cp = (char *)0;", expr(nullPointerConstant())));
+  EXPECT_TRUE(matches("int *ip = 0;", expr(nullPointerConstant())));
+  EXPECT_TRUE(notMatches("int i = 0", expr(nullPointerConstant())));
+}
+
 } // end namespace ast_matchers
 } // end namespace clang
Index: lib/ASTMatchers/Dynamic/Registry.cpp
===================================================================
--- lib/ASTMatchers/Dynamic/Registry.cpp
+++ lib/ASTMatchers/Dynamic/Registry.cpp
@@ -326,6 +326,7 @@
   REGISTER_MATCHER(namesType);
   REGISTER_MATCHER(nestedNameSpecifier);
   REGISTER_MATCHER(nestedNameSpecifierLoc);
+  REGISTER_MATCHER(nullPointerConstant);
   REGISTER_MATCHER(nullStmt);
   REGISTER_MATCHER(numSelectorArgs);
   REGISTER_MATCHER(ofClass);
Index: include/clang/ASTMatchers/ASTMatchers.h
===================================================================
--- include/clang/ASTMatchers/ASTMatchers.h
+++ include/clang/ASTMatchers/ASTMatchers.h
@@ -4816,6 +4816,27 @@
   Stmt,
   CUDAKernelCallExpr> cudaKernelCallExpr;
 
+
+/// \brief Matches expressions that resolve to a null pointer constant, such as
+/// GNU's __null, C++11's nullptr, or C's NULL macro.
+///
+/// Given:
+/// \code
+///   void *v1 = NULL;
+///   void *v2 = nullptr;
+///   void *v3 = __null; // GNU extension
+///   char *cp = (char *)0;
+///   int *ip = 0;
+///   int i = 0;
+/// \endcode
+/// expr(nullPointerConstant())
+///   matches the initializer for v1, v2, v3, cp, and ip. Does not match the
+///   initializer for i.
+AST_MATCHER_FUNCTION(internal::Matcher<Expr>, nullPointerConstant) {
+  return anyOf(
+      gnuNullExpr(), cxxNullPtrLiteralExpr(),
+      expr(integerLiteral(equals(0), hasParent(expr(hasType(pointerType()))))));
+}
 } // end namespace ast_matchers
 } // end namespace clang
 
Index: docs/LibASTMatchersReference.html
===================================================================
--- docs/LibASTMatchersReference.html
+++ docs/LibASTMatchersReference.html
@@ -2176,6 +2176,23 @@
 </pre></td></tr>
 
 
+<tr><td>Matcher<<a href="http://clang.llvm.org/doxygen/classclang_1_1Expr.html">Expr</a>></td><td class="name" onclick="toggle('nullPointerConstant0')"><a name="nullPointerConstant0Anchor">nullPointerConstant</a></td><td></td></tr>
+<tr><td colspan="4" class="doc" id="nullPointerConstant0"><pre>Matches expressions that resolve to a null pointer constant, such as
+GNU's __null, C++11's nullptr, or C's NULL macro.
+
+Given:
+  void *v1 = NULL;
+  void *v2 = nullptr;
+  void *v3 = __null; GNU extension
+  char *cp = (char *)0;
+  int *ip = 0;
+  int i = 0;
+expr(nullPointerConstant())
+  matches the initializer for v1, v2, v3, cp, and ip. Does not match the
+  initializer for i.
+</pre></td></tr>
+
+
 <tr><td>Matcher<<a href="http://clang.llvm.org/doxygen/classclang_1_1FloatingLiteral.html">FloatingLiteral</a>></td><td class="name" onclick="toggle('equals1')"><a name="equals1Anchor">equals</a></td><td>ValueT  Value</td></tr>
 <tr><td colspan="4" class="doc" id="equals1"><pre>Matches literals that are equal to the given value.
 


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