Re: C++ PATCH for c++/81525, auto and generic lambda

2017-10-04 Thread Jason Merrill 
On Wed, Aug 9, 2017 at 3:20 PM, Jason Merrill  wrote:
> In this testcase, when building up an extra version of N to refer to
> when instantiating the generic lambda, we were mistakenly replacing
> the 'auto' with a template argument for the generic lambda.
>
> Tested x86_64-pc-linux-gnu, applying to trunk and 7.

Recent testing found a bug in this patch, whereby we would mistakenly
clobber the TREE_VEC_LENGTH of a single-level argument set, or
increase the length rather than decreasing it.  Fixed by using
strip_innermost_template_args and calculating how many levels we
actually want to remove.  On the trunk I've also added an assert that
we shouldn't get into this situation anymore.

Tested x86_64-pc-linux-gnu, applying to trunk and 7.
commit 2e694fe9477fefb4d746943c6996785109f61aa6
Author: Jason Merrill 
Date:   Thu Sep 28 16:07:34 2017 -0400

PR c++/81525 - broken handling of auto in generic lambda.

* pt.c (tsubst_decl) [VAR_DECL]: Use strip_innermost_template_args.

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index f3ad6083190..38d7b45eb9b 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -12896,15 +12896,17 @@ tsubst_decl (tree t, tree args, tsubst_flags_t 
complain)
&& VAR_HAD_UNKNOWN_BOUND (t)
&& type != error_mark_node)
  type = strip_array_domain (type);
-   tree auto_node = type_uses_auto (type);
-   int len = TREE_VEC_LENGTH (args);
-   if (auto_node)
- /* Mask off any template args past the variable's context so we
-don't replace the auto with an unrelated argument.  */
- TREE_VEC_LENGTH (args) = TEMPLATE_TYPE_LEVEL (auto_node) - 1;
-   type = tsubst (type, args, complain, in_decl);
-   if (auto_node)
- TREE_VEC_LENGTH (args) = len;
+   tree sub_args = args;
+   if (tree auto_node = type_uses_auto (type))
+ {
+   /* Mask off any template args past the variable's context so we
+  don't replace the auto with an unrelated argument.  */
+   int nouter = TEMPLATE_TYPE_LEVEL (auto_node) - 1;
+   int extra = TMPL_ARGS_DEPTH (args) - nouter;
+   if (extra > 0)
+ sub_args = strip_innermost_template_args (args, extra);
+ }
+   type = tsubst (type, sub_args, complain, in_decl);
  }
if (VAR_P (r))
  {
diff --git a/gcc/testsuite/g++.dg/cpp1y/lambda-generic-auto1.C 
b/gcc/testsuite/g++.dg/cpp1y/lambda-generic-auto1.C
new file mode 100644
index 000..b9e98c551c0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/lambda-generic-auto1.C
@@ -0,0 +1,19 @@
+// Related to c++/81525
+// { dg-do compile { target c++14 } }
+
+template 
+struct A
+{
+  template 
+  static void f()
+  {
+[](auto b) {
+  auto c = +b;
+}(42);
+  }
+};
+
+int main()
+{
+  A::f();
+}
commit c6c77e3c274bc8a1bdd33be58895e1ae08a453a7
Author: Jason Merrill 
Date:   Thu Sep 28 16:07:34 2017 -0400

PR c++/81525 - broken handling of auto in generic lambda.

* pt.c (tsubst_decl) [VAR_DECL]: Use strip_innermost_template_args.

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index c29c779a147..36c8c106439 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -13042,15 +13042,20 @@ tsubst_decl (tree t, tree args, tsubst_flags_t 
complain)
&& VAR_HAD_UNKNOWN_BOUND (t)
&& type != error_mark_node)
  type = strip_array_domain (type);
-   tree auto_node = type_uses_auto (type);
-   int len = TREE_VEC_LENGTH (args);
-   if (auto_node)
- /* Mask off any template args past the variable's context so we
-don't replace the auto with an unrelated argument.  */
- TREE_VEC_LENGTH (args) = TEMPLATE_TYPE_LEVEL (auto_node) - 1;
-   type = tsubst (type, args, complain, in_decl);
-   if (auto_node)
- TREE_VEC_LENGTH (args) = len;
+   tree sub_args = args;
+   if (tree auto_node = type_uses_auto (type))
+ {
+   /* Mask off any template args past the variable's context so we
+  don't replace the auto with an unrelated argument.  */
+   int nouter = TEMPLATE_TYPE_LEVEL (auto_node) - 1;
+   int extra = TMPL_ARGS_DEPTH (args) - nouter;
+   if (extra > 0)
+ /* This should never happen with the new lambda instantiation
+model, but keep the handling just in case.  */
+ gcc_assert (!CHECKING_P),
+ sub_args = strip_innermost_template_args (args, extra);
+ }
+   type = tsubst (type, sub_args, complain, in_decl);
  }
if (VAR_P (r))
  {
diff --git a/gcc/testsuite/g++.dg/cpp1y/lambda-generic-auto1.C 
b/gcc/testsuite/g++.dg/cpp1y/lambda-generic-auto1.C
new file mode

C++ PATCH for c++/81525, auto and generic lambda

2017-08-09 Thread Jason Merrill 
In this testcase, when building up an extra version of N to refer to
when instantiating the generic lambda, we were mistakenly replacing
the 'auto' with a template argument for the generic lambda.

Tested x86_64-pc-linux-gnu, applying to trunk and 7.
commit e42e1cc162267b85adfb624daf1b96fc2f5a6f5b
Author: Jason Merrill 
Date:   Mon Aug 7 15:05:51 2017 -0400

PR c++/81525 - wrong constant value with generic lambda

* pt.c (tsubst_decl) [VAR_DECL]: Avoid clobbering auto.
(tsubst_copy) [VAR_DECL]: Handle auto.

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 3d6f4b5..0f899b9 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -12875,7 +12875,15 @@ tsubst_decl (tree t, tree args, tsubst_flags_t 
complain)
&& VAR_HAD_UNKNOWN_BOUND (t)
&& type != error_mark_node)
  type = strip_array_domain (type);
+   tree auto_node = type_uses_auto (type);
+   int len = TREE_VEC_LENGTH (args);
+   if (auto_node)
+ /* Mask off any template args past the variable's context so we
+don't replace the auto with an unrelated argument.  */
+ TREE_VEC_LENGTH (args) = TEMPLATE_TYPE_LEVEL (auto_node) - 1;
type = tsubst (type, args, complain, in_decl);
+   if (auto_node)
+ TREE_VEC_LENGTH (args) = len;
  }
if (VAR_P (r))
  {
@@ -14656,6 +14664,10 @@ tsubst_copy (tree t, tree args, tsubst_flags_t 
complain, tree in_decl)
DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (r)
  = TREE_CONSTANT (r) = true;
  DECL_INITIAL (r) = init;
+ if (tree auto_node = type_uses_auto (TREE_TYPE (r)))
+   TREE_TYPE (r)
+ = do_auto_deduction (TREE_TYPE (r), init, auto_node,
+  complain, adc_variable_type);
}
  gcc_assert (cp_unevaluated_operand || TREE_STATIC (r)
  || decl_constant_var_p (r)
diff --git a/gcc/testsuite/g++.dg/cpp1y/lambda-generic-const4.C 
b/gcc/testsuite/g++.dg/cpp1y/lambda-generic-const4.C
new file mode 100644
index 000..52f4373
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/lambda-generic-const4.C
@@ -0,0 +1,20 @@
+// PR c++/81525
+// { dg-do compile { target c++14 } }
+
+template  struct A {
+  constexpr operator int () const { return i; }
+};
+template  constexpr A a = {};
+
+template  void foo (F f) {
+  f (A<0>{});
+}
+template 
+void bar (T) {
+  constexpr auto N = a<1>;
+  auto f = [&] (auto i) {
+static_assert (static_cast(N) == 1, "");
+  };
+  foo (f);
+}
+int main () { bar (0); }