Re: [PATCH] [PR c++/84943] allow folding of array indexing indirect_ref

[Alexandre Oliva <aoliva@redhat.com>]

On Mar 30, 2018, Jason Merrill <jason@redhat.com> wrote:

> I don't think we need this; if arg is overloaded, we take the
> type_unknown_p early exit, so the code lower down is always dealing
> with a single function.

Aah, that's why it seemed to me that we had already resolved overloads
when we got there.

As a bonus, I added the tf_conv test before another mark_used call I'd
missed in the previous patch.

Regstrapped on i686- and x86_64-linux-gnu.  Ok to install?


[PR c++/84943] mark function as used when taking its address

fn[0]() ICEd because we would fold the INDIRECT_REF used for the
array indexing while building the address for the call, after not
finding the decl hiding there at first.  But the decl would be exposed
by the folding, and then lower layers would complain we had the decl,
after all, but it wasn't one of the artificial or special functions
that could be called without being marked as used.

This patch arranges for a FUNCTION_DECL to be marked as used when
taking its address, just like we already did when taking the address
of a static function to call it as a member function (i.e. using the
obj.fn() notation).  However, we shouldn't mark functions as used when
just performing overload resolution, lest we might instantiate
templates we shouldn't, as in g++.dg/overload/template1.C.


for  gcc/cp/ChangeLog

	PR c++/84943
	* typeck.c (cp_build_addr_expr_1): Mark FUNCTION_DECL as
	used.

for  gcc/testsuite/ChangeLog

	PR c++/84943
	* g++.dg/pr84943.C: New.
	* g++.dg/pr84943-2.C: New.
---
 gcc/cp/typeck.c                  |    9 ++++-
 gcc/testsuite/g++.dg/pr84943-2.C |   64 ++++++++++++++++++++++++++++++++++++++
 gcc/testsuite/g++.dg/pr84943.C   |    8 +++++
 3 files changed, 79 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/pr84943-2.C
 create mode 100644 gcc/testsuite/g++.dg/pr84943.C

diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index d454c6c5a295..bdb2bb30a583 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -5801,7 +5801,8 @@ cp_build_addr_expr_1 (tree arg, bool strict_lvalue, tsubst_flags_t complain)
 	 and the created OFFSET_REF.  */
       tree base = TYPE_MAIN_VARIANT (TREE_TYPE (TREE_OPERAND (arg, 0)));
       tree fn = get_first_fn (TREE_OPERAND (arg, 1));
-      if (!mark_used (fn, complain) && !(complain & tf_error))
+      if (!(complain & tf_conv)
+	  && !mark_used (fn, complain) && !(complain & tf_error))
 	return error_mark_node;
 
       if (! flag_ms_extensions)
@@ -5971,6 +5972,9 @@ cp_build_addr_expr_1 (tree arg, bool strict_lvalue, tsubst_flags_t complain)
      so we can just form an ADDR_EXPR with the correct type.  */
   if (processing_template_decl || TREE_CODE (arg) != COMPONENT_REF)
     {
+      if (TREE_CODE (arg) == FUNCTION_DECL && !(complain & tf_conv)
+	  && !mark_used (arg, complain) && !(complain & tf_error))
+	return error_mark_node;
       val = build_address (arg);
       if (TREE_CODE (arg) == OFFSET_REF)
 	PTRMEM_OK_P (val) = PTRMEM_OK_P (arg);
@@ -5983,7 +5987,8 @@ cp_build_addr_expr_1 (tree arg, bool strict_lvalue, tsubst_flags_t complain)
 	 function.  */
       gcc_assert (TREE_CODE (fn) == FUNCTION_DECL
 		  && DECL_STATIC_FUNCTION_P (fn));
-      if (!mark_used (fn, complain) && !(complain & tf_error))
+      if (!(complain & tf_conv)
+	  && !mark_used (fn, complain) && !(complain & tf_error))
 	return error_mark_node;
       val = build_address (fn);
       if (TREE_SIDE_EFFECTS (TREE_OPERAND (arg, 0)))
diff --git a/gcc/testsuite/g++.dg/pr84943-2.C b/gcc/testsuite/g++.dg/pr84943-2.C
new file mode 100644
index 000000000000..d1ef012b9155
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr84943-2.C
@@ -0,0 +1,64 @@
+// { dg-do run }
+
+// Avoid -pedantic-error default
+// { dg-options "" }
+
+// Make sure the functions referenced by various forms of
+// address-taking are marked as used and compiled in.
+
+static void ac() {}
+void a() {
+  ac[0](); // { dg-warning "arithmetic" }
+}
+
+static void bc() {}
+void b() {
+  (&*&*&*&bc)();
+}
+
+template <typename U> U cc() {}
+void (*c())() {
+  return cc;
+}
+
+template <typename T>
+struct x {
+  void a(int);
+  template <typename U> static U a(x*) {}
+  static void a(long) {}
+  static void a(void *) {}
+  static void a() {
+    void (*p0)(void*) = x().a;
+    p0(0);
+    void (*p1)(long) = a;
+    p1(0);
+    void (*p2)() = a;
+    p2();
+    void (*p3)(x*) = a;
+    p3(0);
+  }
+};
+
+struct z {
+  void a(int);
+  template <typename U> static U a(z*) {}
+  static void a(long) {}
+  static void a(void *) {}
+  static void a() {
+    void (*p0)(void*) = z().a;
+    p0(0);
+    void (*p1)(long) = a;
+    p1(0);
+    void (*p2)() = a;
+    p2();
+    void (*p3)(z*) = a;
+    p3(0);
+  }
+};
+
+int main(int argc, char *argv[]) {
+  if (argc > 1) {
+    x<void>().a();
+    z().a();
+  }
+}
diff --git a/gcc/testsuite/g++.dg/pr84943.C b/gcc/testsuite/g++.dg/pr84943.C
new file mode 100644
index 000000000000..36f75a164119
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr84943.C
@@ -0,0 +1,8 @@
+// { dg-do compile }
+
+// Avoid -pedantic-error default
+// { dg-options "" }
+
+void a() {
+  a[0](); // { dg-warning "arithmetic" }
+}


-- 
Alexandre Oliva, freedom fighter    http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/   FSF Latin America board member
Free Software Evangelist|Red Hat Brasil GNU Toolchain Engineer