[PATCH] Fix some blockers of PR c++/24666 (arrays decay to pointers too early)

[Patrick Palka]

On Wed, 16 Dec 2015, Jason Merrill wrote:

> On 12/15/2015 04:16 PM, Patrick Palka wrote:
>> +  if (MAYBE_CLASS_TYPE_P (type))
>> +    ;
>
> What does this patch do with conversion to const reference to class?  I think 
> we want to check MAYBE_CLASS_TYPE_P (non_reference (type)) here.

That makes sense.  Here's an updated patch using non_reference, with
tests updated to each have a reference-returning variant.

-- 8< --

gcc/cp/ChangeLog:

 	PR c++/16333
 	PR c++/41426
 	PR c++/59878
 	PR c++/66895
 	* typeck.c (convert_for_initialization): Don't perform an early
 	decaying conversion if converting to a class type.

gcc/testsuite/ChangeLog:

 	PR c++/16333
 	PR c++/41426
 	PR c++/59878
 	PR c++/66895
 	* g++.dg/conversion/pr16333.C: New test.
 	* g++.dg/conversion/pr41426.C: New test.
 	* g++.dg/conversion/pr59878.C: New test.
 	* g++.dg/conversion/pr66895.C: New test.
---
  gcc/cp/typeck.c                           | 16 +++++++------
  gcc/testsuite/g++.dg/conversion/pr16333.C | 10 ++++++++
  gcc/testsuite/g++.dg/conversion/pr41426.C | 40 +++++++++++++++++++++++++++++++
  gcc/testsuite/g++.dg/conversion/pr59878.C | 25 +++++++++++++++++++
  gcc/testsuite/g++.dg/conversion/pr66895.C | 16 +++++++++++++
  5 files changed, 100 insertions(+), 7 deletions(-)
  create mode 100644 gcc/testsuite/g++.dg/conversion/pr16333.C
  create mode 100644 gcc/testsuite/g++.dg/conversion/pr41426.C
  create mode 100644 gcc/testsuite/g++.dg/conversion/pr59878.C
  create mode 100644 gcc/testsuite/g++.dg/conversion/pr66895.C

diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index 39c1af2..a06ecf0 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -8479,13 +8479,15 @@ convert_for_initialization (tree exp, tree type, tree rhs, int flags,
        || (TREE_CODE (rhs) == TREE_LIST && TREE_VALUE (rhs) == error_mark_node))
      return error_mark_node;

-  if ((TREE_CODE (TREE_TYPE (rhs)) == ARRAY_TYPE
-       && TREE_CODE (type) != ARRAY_TYPE
-       && (TREE_CODE (type) != REFERENCE_TYPE
-	   || TREE_CODE (TREE_TYPE (type)) != ARRAY_TYPE))
-      || (TREE_CODE (TREE_TYPE (rhs)) == FUNCTION_TYPE
-	  && !TYPE_REFFN_P (type))
-      || TREE_CODE (TREE_TYPE (rhs)) == METHOD_TYPE)
+  if (MAYBE_CLASS_TYPE_P (non_reference (type)))
+    ;
+  else if ((TREE_CODE (TREE_TYPE (rhs)) == ARRAY_TYPE
+	    && TREE_CODE (type) != ARRAY_TYPE
+	    && (TREE_CODE (type) != REFERENCE_TYPE
+		|| TREE_CODE (TREE_TYPE (type)) != ARRAY_TYPE))
+	   || (TREE_CODE (TREE_TYPE (rhs)) == FUNCTION_TYPE
+	       && !TYPE_REFFN_P (type))
+	   || TREE_CODE (TREE_TYPE (rhs)) == METHOD_TYPE)
      rhs = decay_conversion (rhs, complain);

    rhstype = TREE_TYPE (rhs);
diff --git a/gcc/testsuite/g++.dg/conversion/pr16333.C b/gcc/testsuite/g++.dg/conversion/pr16333.C
new file mode 100644
index 0000000..810c12a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/conversion/pr16333.C
@@ -0,0 +1,10 @@
+// PR c++/16333
+
+struct X {
+   X (const int (&)[3]);
+};
+
+int a[3];
+X foo1 () { return a; }
+const X &foo2 () { return a; } // { dg-warning "returning reference to temporary" }
+X &foo3 () { return a; } // { dg-error "invalid initialization" }
diff --git a/gcc/testsuite/g++.dg/conversion/pr41426.C b/gcc/testsuite/g++.dg/conversion/pr41426.C
new file mode 100644
index 0000000..78ec5fb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/conversion/pr41426.C
@@ -0,0 +1,40 @@
+// PR c++/41426
+
+template <typename _T>
+struct A
+{
+   template <int _N>
+       A(_T (&V)[_N]);
+   A();
+};
+
+A<float> g1()
+{
+   float f[] = {1.1f, 2.3f};
+   return f;
+}
+
+const A<float> &g3()
+{
+   float f[] = {1.1f, 2.3f};
+   return f; // { dg-warning "returning reference to temporary" }
+}
+
+A<float> &g4()
+{
+   float f[] = {1.1f, 2.3f};
+   return f; // { dg-error "invalid initialization" }
+}
+
+struct B
+{
+   B (int (&v)[10]);
+   B();
+};
+
+B g2()
+{
+   int c[10];
+   return c;
+}
+
diff --git a/gcc/testsuite/g++.dg/conversion/pr59878.C b/gcc/testsuite/g++.dg/conversion/pr59878.C
new file mode 100644
index 0000000..ed567fe
--- /dev/null
+++ b/gcc/testsuite/g++.dg/conversion/pr59878.C
@@ -0,0 +1,25 @@
+// PR c++/59878
+
+struct Test {
+ template <int N>
+ Test(const char (&array)[N]) {}
+};
+
+Test test() {
+ return "test1";
+}
+
+void test2(Test arg = "test12") {}
+
+template <typename T>
+void test3(T arg = "test123") {}
+
+template <typename T>
+void test4(const T &arg = "test123") {}
+
+int main() {
+ test();
+ test2();
+ test3<Test>();
+ test4<Test>();
+}
diff --git a/gcc/testsuite/g++.dg/conversion/pr66895.C b/gcc/testsuite/g++.dg/conversion/pr66895.C
new file mode 100644
index 0000000..14203bd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/conversion/pr66895.C
@@ -0,0 +1,16 @@
+// PR c++/66895
+// { dg-do compile { target c++11 } }
+
+#include <cstddef>
+#include <initializer_list>
+
+struct S {
+    template<std::size_t N> S(char const (&)[N]);
+};
+struct T1 { S s; };
+void f1(std::initializer_list<T1>);
+void g1() { f1({{""}}); }
+
+struct T2 { const S& s; };
+void f2(std::initializer_list<T2>);
+void g2() { f2({{""}}); }
-- 
2.7.0.rc0.50.g1470d8f.dirty