PR16074, implement warnings to catch pointer to boolean true and pointer to

null comparison when the pointer is known to be non-null.

This catches the array to pointer decay, function to pointer decay and
address of variables.  This does not catch address of function since this
has been previously used to silence a warning.

Pointer to bool conversion is under -Wbool-conversion.
Pointer to null comparison is under -Wtautological-pointer-compare, a sub-group
of -Wtautological-compare.

void foo() {
  int arr[5];
  int x;
  // warn on these conditionals
  if (foo);
  if (arr);
  if (&x);
  if (foo == null);
  if (arr == null);
  if (&x == null);

  if (&foo);  // no warning
}

llvm-svn: 202216

1 files changed, 96 insertions, 0 deletions

diff --git a/clang/test/SemaCXX/warn-bool-conversion.cpp b/clang/test/SemaCXX/warn-bool-conversion.cpp
index b3d136ecf2b..b4628947f06 100644
--- a/clang/test/SemaCXX/warn-bool-conversion.cpp
+++ b/clang/test/SemaCXX/warn-bool-conversion.cpp
@@ -1,5 +1,6 @@
 // RUN: %clang_cc1 -fsyntax-only -verify %s
 
+namespace BooleanFalse {
 int* j = false; // expected-warning{{initialization of pointer of type 'int *' to null from a constant boolean expression}}
 
 void foo(int* i, int *j=(false)) // expected-warning{{initialization of pointer of type 'int *' to null from a constant boolean expression}}
@@ -22,3 +23,98 @@ double f(...);
 // isn't flagged.
 template <int N> struct S {};
 S<sizeof(f(false))> s;
+
+}
+
+namespace Function {
+void f1();
+
+struct S {
+  static void f2();
+};
+
+extern void f3() __attribute__((weak_import));
+
+struct S2 {
+  static void f4() __attribute__((weak_import));
+};
+
+bool f5();
+bool f6(int);
+
+void bar() {
+  bool b;
+
+  b = f1; // expected-warning {{address of function 'f1' will always evaluate to 'true'}} \
+             expected-note {{prefix with the address-of operator to silence this warning}}
+  if (f1) {} // expected-warning {{address of function 'f1' will always evaluate to 'true'}} \
+                expected-note {{prefix with the address-of operator to silence this warning}}
+  b = S::f2; // expected-warning {{address of function 'S::f2' will always evaluate to 'true'}} \
+                expected-note {{prefix with the address-of operator to silence this warning}}
+  if (S::f2) {} // expected-warning {{address of function 'S::f2' will always evaluate to 'true'}} \
+                   expected-note {{prefix with the address-of operator to silence this warning}}
+  b = f5; // expected-warning {{address of function 'f5' will always evaluate to 'true'}} \
+             expected-note {{prefix with the address-of operator to silence this warning}} \
+             expected-note {{suffix with parentheses to turn this into a function call}}
+  b = f6; // expected-warning {{address of function 'f6' will always evaluate to 'true'}} \
+             expected-note {{prefix with the address-of operator to silence this warning}}
+
+  // implicit casts of weakly imported symbols are ok:
+  b = f3;
+  if (f3) {}
+  b = S2::f4;
+  if (S2::f4) {}
+}
+}
+
+namespace Array {
+  #define GetValue(ptr)  ((ptr) ? ptr[0] : 0)
+  extern int a[] __attribute__((weak));
+  int b[] = {8,13,21};
+  struct {
+    int x[10];
+  } c;
+  const char str[] = "text";
+  void ignore() {
+    if (a) {}
+    if (a) {}
+    (void)GetValue(b);
+  }
+  void test() {
+    if (b) {}
+    // expected-warning@-1{{address of array 'b' will always evaluate to 'true'}}
+    if (b) {}
+    // expected-warning@-1{{address of array 'b' will always evaluate to 'true'}}
+    if (c.x) {}
+    // expected-warning@-1{{address of array 'c.x' will always evaluate to 'true'}}
+    if (str) {}
+    // expected-warning@-1{{address of array 'str' will always evaluate to 'true'}}
+  }
+}
+
+namespace Pointer {
+  extern int a __attribute__((weak));
+  int b;
+  static int c;
+  class S {
+  public:
+    static int a;
+    int b;
+  };
+  void ignored() {
+    if (&a) {}
+  }
+  void test() {
+    S s;
+    if (&b) {}
+    // expected-warning@-1{{address of 'b' will always evaluate to 'true'}}
+    if (&c) {}
+    // expected-warning@-1{{address of 'c' will always evaluate to 'true'}}
+    if (&s.a) {}
+    // expected-warning@-1{{address of 's.a' will always evaluate to 'true'}}
+    if (&s.b) {}
+    // expected-warning@-1{{address of 's.b' will always evaluate to 'true'}}
+    if (&S::a) {}
+    // expected-warning@-1{{address of 'S::a' will always evaluate to 'true'}}
+  }
+}