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* [gcc r12-7630] c++: ICE with non-constant satisfaction value [PR98644]
@ 2022-03-12 20:02 Patrick Palka
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From: Patrick Palka @ 2022-03-12 20:02 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:ab71d3fe4b23af4c29a8d6fcf1e914fed4393e3b
commit r12-7630-gab71d3fe4b23af4c29a8d6fcf1e914fed4393e3b
Author: Patrick Palka <ppalka@redhat.com>
Date: Sat Mar 12 14:57:59 2022 -0500
c++: ICE with non-constant satisfaction value [PR98644]
Here during satisfaction, the expression of the atomic constraint after
substitution is (int *) NON_LVALUE_EXPR <1> != 0B, which is not a C++
constant expression due to the reinterpret_cast, but TREE_CONSTANT is
set since its value is otherwise effectively constant. We then call
maybe_constant_value on it, which proceeds via its fail-fast path to
exit early without clearing TREE_CONSTANT. But satisfy_atom relies
on checking TREE_CONSTANT of the result of maybe_constant_value in order
to detect non-constant satisfaction.
This patch fixes this by making the fail-fast path of maybe_constant_value
clear TREE_CONSTANT in this case, like cxx_eval_outermost_constant_expr
in the normal path would have done.
PR c++/98644
gcc/cp/ChangeLog:
* constexpr.cc (mark_non_constant): Define, split out from ...
(cxx_eval_outermost_constant_expr): ... here.
(maybe_constant_value): Use it.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-pr98644.C: New test.
* g++.dg/parse/array-size2.C: Remove expected diagnostic about a
narrowing conversion.
Co-authored-by: Jason Merrill <jason@redhat.com>
Diff:
---
gcc/cp/constexpr.cc | 46 ++++++++++++++++-----------
gcc/testsuite/g++.dg/cpp2a/concepts-pr98644.C | 7 ++++
gcc/testsuite/g++.dg/parse/array-size2.C | 2 --
3 files changed, 34 insertions(+), 21 deletions(-)
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 388957913be..bbb6cd99b3c 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -7579,6 +7579,29 @@ find_immediate_fndecl (tree *tp, int */*walk_subtrees*/, void */*data*/)
return NULL_TREE;
}
+/* T has TREE_CONSTANT set but has been deemed not a valid C++ constant
+ expression. Return a version of T that has TREE_CONSTANT cleared. */
+
+static tree
+mark_non_constant (tree t)
+{
+ gcc_checking_assert (TREE_CONSTANT (t));
+
+ /* This isn't actually constant, so unset TREE_CONSTANT.
+ Don't clear TREE_CONSTANT on ADDR_EXPR, as the middle-end requires
+ it to be set if it is invariant address, even when it is not
+ a valid C++ constant expression. Wrap it with a NOP_EXPR
+ instead. */
+ if (EXPR_P (t) && TREE_CODE (t) != ADDR_EXPR)
+ t = copy_node (t);
+ else if (TREE_CODE (t) == CONSTRUCTOR)
+ t = build1 (VIEW_CONVERT_EXPR, TREE_TYPE (t), t);
+ else
+ t = build_nop (TREE_TYPE (t), t);
+ TREE_CONSTANT (t) = false;
+ return t;
+}
+
/* ALLOW_NON_CONSTANT is false if T is required to be a constant expression.
STRICT has the same sense as for constant_value_1: true if we only allow
conforming C++ constant expressions, or false if we want a constant value
@@ -7801,20 +7824,7 @@ cxx_eval_outermost_constant_expr (tree t, bool allow_non_constant,
else if (constexpr_dtor)
return r;
else if (non_constant_p && TREE_CONSTANT (r))
- {
- /* This isn't actually constant, so unset TREE_CONSTANT.
- Don't clear TREE_CONSTANT on ADDR_EXPR, as the middle-end requires
- it to be set if it is invariant address, even when it is not
- a valid C++ constant expression. Wrap it with a NOP_EXPR
- instead. */
- if (EXPR_P (r) && TREE_CODE (r) != ADDR_EXPR)
- r = copy_node (r);
- else if (TREE_CODE (r) == CONSTRUCTOR)
- r = build1 (VIEW_CONVERT_EXPR, TREE_TYPE (r), r);
- else
- r = build_nop (TREE_TYPE (r), r);
- TREE_CONSTANT (r) = false;
- }
+ r = mark_non_constant (r);
else if (non_constant_p)
return t;
@@ -7965,11 +7975,9 @@ maybe_constant_value (tree t, tree decl, bool manifestly_const_eval)
if (!is_nondependent_constant_expression (t))
{
- if (TREE_OVERFLOW_P (t))
- {
- t = build_nop (TREE_TYPE (t), t);
- TREE_CONSTANT (t) = false;
- }
+ if (TREE_OVERFLOW_P (t)
+ || (!processing_template_decl && TREE_CONSTANT (t)))
+ t = mark_non_constant (t);
return t;
}
else if (CONSTANT_CLASS_P (t))
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-pr98644.C b/gcc/testsuite/g++.dg/cpp2a/concepts-pr98644.C
new file mode 100644
index 00000000000..6772f72a3ce
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-pr98644.C
@@ -0,0 +1,7 @@
+// PR c++/98644
+// { dg-do compile { target c++20 } }
+
+template<class T> concept Signed = bool(T(1)); // { dg-error "reinterpret_cast" }
+static_assert(Signed<int*>); // { dg-error "non-constant" }
+
+constexpr bool B = requires { requires bool((char *)1); }; // { dg-error "reinterpret_cast" }
diff --git a/gcc/testsuite/g++.dg/parse/array-size2.C b/gcc/testsuite/g++.dg/parse/array-size2.C
index c4a69df3b01..e58fe266e77 100644
--- a/gcc/testsuite/g++.dg/parse/array-size2.C
+++ b/gcc/testsuite/g++.dg/parse/array-size2.C
@@ -15,8 +15,6 @@ void
foo (void)
{
char g[(char *) &((struct S *) 0)->b - (char *) 0]; // { dg-error "40:size of array .g. is not an integral constant-expression" }
- // { dg-error "narrowing conversion" "" { target c++11 } .-1 }
- // { dg-message "expression has a constant value but is not a C.. constant-expression" "" { target c++11 } .-2 }
char h[(__SIZE_TYPE__) &((struct S *) 8)->b]; // { dg-error "10:size of array .h. is not an integral constant-expression" }
bar (g, h);
}
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