[analyzer] For now, treat pointers-to-members as non-null void * symbols.

Until we have full support for pointers-to-members, we can at least
approximate some of their use by tracking null and non-null values.
We thus treat &A::m_ptr as a non-null void * symbol, and MemberPointer(0)
as a pointer-sized null constant.

This enables support for what is sometimes called the "safe bool" idiom,
demonstrated in the test case.

llvm-svn: 162495

1 files changed, 44 insertions, 0 deletions

diff --git a/clang/test/Analysis/pointer-to-member.cpp b/clang/test/Analysis/pointer-to-member.cpp
new file mode 100644
index 00000000000..cef5dc58669
--- /dev/null
+++ b/clang/test/Analysis/pointer-to-member.cpp
@@ -0,0 +1,44 @@
+// RUN: %clang_cc1 -analyze -analyzer-checker=core,debug.ExprInspection -analyzer-ipa=inlining -verify %s
+
+void clang_analyzer_eval(bool);
+
+struct A {
+  // This conversion operator allows implicit conversion to bool but not to other integer types.
+  typedef A * (A::*MemberPointer);
+  operator MemberPointer() const { return m_ptr ? &A::m_ptr : 0; }
+
+  A *m_ptr;
+};
+
+void testConditionalUse() {
+  A obj;
+
+  obj.m_ptr = &obj;
+  clang_analyzer_eval(obj.m_ptr); // expected-warning{{TRUE}}
+  clang_analyzer_eval(&A::m_ptr); // expected-warning{{TRUE}}
+  clang_analyzer_eval(obj); // expected-warning{{TRUE}}
+
+  obj.m_ptr = 0;
+  clang_analyzer_eval(obj.m_ptr); // expected-warning{{FALSE}}
+  clang_analyzer_eval(A::MemberPointer(0)); // expected-warning{{FALSE}}
+  clang_analyzer_eval(obj); // expected-warning{{FALSE}}
+}
+
+// ---------------
+// FALSE NEGATIVES
+// ---------------
+
+bool testDereferencing() {
+  A obj;
+  obj.m_ptr = 0;
+
+  A::MemberPointer member = &A::m_ptr;
+
+  // FIXME: Should be TRUE.
+  clang_analyzer_eval(obj.*member == 0); // expected-warning{{UNKNOWN}}
+
+  member = 0;
+
+  // FIXME: Should emit a null dereference.
+  return obj.*member; // no-warning
+}