[Sema] Make `&function_with_enable_if_attrs` an error

This fixes a bug where one can take the address of a conditionally
enabled function to drop its enable_if guards. For example:

  int foo(int a) __attribute__((enable_if(a > 0, "")));
  int (*p)(int) = &foo;
  int result = p(-1); // compilation succeeds; calls foo(-1)

Overloading logic has been updated to reflect this change, as well.

Functions with enable_if attributes that are always true are still
allowed to have their address taken.

Differential Revision: http://reviews.llvm.org/D13607

llvm-svn: 250090

1 files changed, 51 insertions, 0 deletions

diff --git a/clang/test/CodeGen/enable_if.c b/clang/test/CodeGen/enable_if.c
new file mode 100644
index 00000000000..d1173d291ad
--- /dev/null
+++ b/clang/test/CodeGen/enable_if.c
@@ -0,0 +1,51 @@
+// RUN: %clang_cc1 -emit-llvm %s -o - -triple=x86_64-pc-linux-gnu | FileCheck %s
+
+// Verifying that we do, in fact, select the correct function in the following
+// cases.
+
+void foo(int m) __attribute__((overloadable, enable_if(m > 0, "")));
+void foo(int m) __attribute__((overloadable));
+
+// CHECK-LABEL: define void @test1
+void test1() {
+  // CHECK: store void (i32)* @_Z3fooi
+  void (*p)(int) = foo;
+  // CHECK: store void (i32)* @_Z3fooi
+  void (*p2)(int) = &foo;
+  // CHECK: store void (i32)* @_Z3fooi
+  p = foo;
+  // CHECK: store void (i32)* @_Z3fooi
+  p = &foo;
+
+  // CHECK: store i8* bitcast (void (i32)* @_Z3fooi to i8*)
+  void *vp1 = (void*)&foo;
+  // CHECK: store i8* bitcast (void (i32)* @_Z3fooi to i8*)
+  void *vp2 = (void*)foo;
+  // CHECK: store i8* bitcast (void (i32)* @_Z3fooi to i8*)
+  vp1 = (void*)&foo;
+  // CHECK: store i8* bitcast (void (i32)* @_Z3fooi to i8*)
+  vp1 = (void*)foo;
+}
+
+void bar(int m) __attribute__((overloadable, enable_if(m > 0, "")));
+void bar(int m) __attribute__((overloadable, enable_if(1, "")));
+// CHECK-LABEL: define void @test2
+void test2() {
+  // CHECK: store void (i32)* @_Z3barUa9enable_ifIXLi1EEEi
+  void (*p)(int) = bar;
+  // CHECK: store void (i32)* @_Z3barUa9enable_ifIXLi1EEEi
+  void (*p2)(int) = &bar;
+  // CHECK: store void (i32)* @_Z3barUa9enable_ifIXLi1EEEi
+  p = bar;
+  // CHECK: store void (i32)* @_Z3barUa9enable_ifIXLi1EEEi
+  p = &bar;
+
+  // CHECK: store i8* bitcast (void (i32)* @_Z3barUa9enable_ifIXLi1EEEi to i8*)
+  void *vp1 = (void*)&bar;
+  // CHECK: store i8* bitcast (void (i32)* @_Z3barUa9enable_ifIXLi1EEEi to i8*)
+  void *vp2 = (void*)bar;
+  // CHECK: store i8* bitcast (void (i32)* @_Z3barUa9enable_ifIXLi1EEEi to i8*)
+  vp1 = (void*)&bar;
+  // CHECK: store i8* bitcast (void (i32)* @_Z3barUa9enable_ifIXLi1EEEi to i8*)
+  vp1 = (void*)bar;
+}