[p0012] Implement ABI support for throwing a noexcept function pointer and

catching as non-noexcept

This implements the following proposal from cxx-abi-dev:

http://sourcerytools.com/pipermail/cxx-abi-dev/2016-October/002988.html

... which is necessary for complete support of http://wg21.link/p0012,
specifically throwing noexcept function and member function pointers and
catching them as non-noexcept pointers.

Differential Review: https://reviews.llvm.org/D26178


git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@285867 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 73 insertions, 1 deletions

diff --git a/src/private_typeinfo.cpp b/src/private_typeinfo.cpp
index 73ef362..6112a1f 100644
--- a/src/private_typeinfo.cpp
+++ b/src/private_typeinfo.cpp
@@ -105,6 +105,45 @@ __function_type_info::~__function_type_info()
 {
 }
 
+// __qualified_function_type_info
+
+__qualified_function_type_info::~__qualified_function_type_info()
+{
+}
+
+// Determine if a function pointer conversion can convert a pointer (or pointer
+// to member) to type x into a pointer (or pointer to member) to type y.
+static bool is_function_pointer_conversion(const std::type_info* x,
+                                           const std::type_info* y)
+{
+    const unsigned int discardable_quals =
+        __qualified_function_type_info::__noexcept_mask |
+        __qualified_function_type_info::__transaction_safe_mask |
+        __qualified_function_type_info::__noreturn_mask;
+
+    // If x has only discardable qualifiers and y is unqualified, then
+    // conversion is permitted.
+    const __qualified_function_type_info* qual_x =
+        dynamic_cast<const __qualified_function_type_info *>(x);
+    if (!qual_x)
+        return false;
+    if ((qual_x->__qualifiers & ~discardable_quals) == 0 &&
+        is_equal(qual_x->__base_type, y, false))
+        return true;
+
+    // Otherwise, x's qualifiers must be the same as y's, plus some discardable
+    // ones.
+    const __qualified_function_type_info* qual_y =
+        dynamic_cast<const __qualified_function_type_info *>(y);
+    if (!qual_y)
+        return false;
+    if (qual_y->__qualifiers & ~qual_x->__qualifiers)
+        return false;
+    if (qual_x->__qualifiers & ~qual_y->__qualifiers & ~discardable_quals)
+        return false;
+    return is_equal(qual_x->__base_type, qual_y->__base_type, false);
+}
+
 // __enum_type_info
 
 __enum_type_info::~__enum_type_info()
@@ -395,6 +434,10 @@ __pointer_type_info::can_catch(const __shim_type_info* thrown_type,
         return false;
     if (is_equal(__pointee, thrown_pointer_type->__pointee, false))
         return true;
+    // bullet 3C
+    if (is_function_pointer_conversion(thrown_pointer_type->__pointee,
+                                       __pointee))
+      return true;
     // bullet 3A
     if (is_equal(__pointee, &typeid(void), false)) {
         // pointers to functions cannot be converted to void*.
@@ -502,7 +545,9 @@ bool __pointer_to_member_type_info::can_catch(
         return false;
     if (thrown_pointer_type->__flags & ~__flags)
         return false;
-    if (!is_equal(__pointee, thrown_pointer_type->__pointee, false))
+    if (!is_equal(__pointee, thrown_pointer_type->__pointee, false) &&
+        !is_function_pointer_conversion(thrown_pointer_type->__pointee,
+                                        __pointee))
         return false;
     if (is_equal(__context, thrown_pointer_type->__context, false))
         return true;
diff --git a/src/private_typeinfo.h b/src/private_typeinfo.h
index ef98c3a..fa6bd63 100644
--- a/src/private_typeinfo.h
+++ b/src/private_typeinfo.h
@@ -49,6 +49,33 @@ public:
                                            void *&) const;
 };
 
+// This implements the following proposal from cxx-abi-dev (not yet part of the
+// ABI document):
+//
+//   http://sourcerytools.com/pipermail/cxx-abi-dev/2016-October/002988.html
+//
+// This is necessary for support of http://wg21.link/p0012, which permits throwing
+// noexcept function and member function pointers and catching them as non-noexcept
+// pointers.
+class _LIBCXXABI_TYPE_VIS __qualified_function_type_info : public __shim_type_info {
+public:
+  const __function_type_info* __base_type;
+  unsigned int __qualifiers;
+
+  enum __qualifiers_mask {
+    __const_mask = 0x01,
+    __volatile_mask = 0x02,
+    __restrict_mask = 0x04,
+    __lval_ref_mask = 0x08,
+    __rval_ref_mask = 0x10,
+    __noexcept_mask = 0x20,
+    __transaction_safe_mask = 0x40,
+    __noreturn_mask = 0x80
+  };
+
+  _LIBCXXABI_HIDDEN virtual ~__qualified_function_type_info();
+};
+
 class _LIBCXXABI_TYPE_VIS __enum_type_info : public __shim_type_info {
 public:
   _LIBCXXABI_HIDDEN virtual ~__enum_type_info();