On Tue, Oct 19, 2021 at 02:00:21PM +0200, Jakub Jelinek via Gcc-patches wrote:
> And another thing isn't in a patch, but I'm wondering whether we don't
> handle it incorrectly. constexpr.c has:
> /* Check that immediate invocation does not return an expression referencing
> any immediate function decls. They need to be allowed while parsing
> immediate functions, but can't leak outside of them. */
> if (is_consteval
> && t != r
> && (current_function_decl == NULL_TREE
> || !DECL_IMMEDIATE_FUNCTION_P (current_function_decl)))
> as condition for the discovery of embedded immediate FUNCTION_DECLs
> (or now PTRMEM_CSTs). If I remove the && (current... ..._decl))
> then g++.dg/cpp2a/consteval7.C's
> struct S { int b; int (*c) (); };
> consteval S baz () { return { 5, foo }; }
> consteval int qux () { S s = baz (); return s.b + s.c (); }
> consteval int quux () { constexpr S s = baz (); return s.b + s.c (); }
> quux line fails, but based on
> http://eel.is/c++draft/expr.const#11
> I wonder if it shouldn't fail (clang++ -std=c++20 rejects it),
> and be only accepted without the constexpr keyword before S s.
Here is an incremental patch that implements that.
2021-10-19 Jakub Jelinek <ja...@redhat.com>
PR c++/102753
* constexpr.c (cxx_eval_outermost_constant_expr): Perform
find_immediate_fndecl discovery if is_consteval or
in_immediate_context () rather than if is_consteval, t != r
and not in immediate function's body.
* g++.dg/cpp2a/consteval7.C: Expect diagnostics on quux.
* g++.dg/cpp2a/consteval24.C: New test.
* g++.dg/cpp23/consteval-if12.C: New test.
--- gcc/cp/constexpr.c.jj 2021-10-19 12:22:35.583964001 +0200
+++ gcc/cp/constexpr.c 2021-10-19 13:58:22.545182032 +0200
@@ -7472,12 +7472,8 @@ cxx_eval_outermost_constant_expr (tree t
}
/* Check that immediate invocation does not return an expression referencing
- any immediate function decls. They need to be allowed while parsing
- immediate functions, but can't leak outside of them. */
- if (is_consteval
- && t != r
- && (current_function_decl == NULL_TREE
- || !DECL_IMMEDIATE_FUNCTION_P (current_function_decl)))
+ any immediate function decls. */
+ if (is_consteval || in_immediate_context ())
if (tree immediate_fndecl
= cp_walk_tree_without_duplicates (&r, find_immediate_fndecl,
NULL))
--- gcc/testsuite/g++.dg/cpp2a/consteval7.C.jj 2020-01-12 11:54:37.140402440
+0100
+++ gcc/testsuite/g++.dg/cpp2a/consteval7.C 2021-10-19 13:59:54.033897061
+0200
@@ -7,7 +7,7 @@ constexpr auto a = bar (); // { dg-error
struct S { int b; int (*c) (); };
consteval S baz () { return { 5, foo }; }
consteval int qux () { S s = baz (); return s.b + s.c (); }
-consteval int quux () { constexpr S s = baz (); return s.b + s.c (); }
+consteval int quux () { constexpr S s = baz (); return s.b + s.c (); } // {
dg-error "immediate evaluation returns address of immediate function 'consteval
int foo\\(\\)'" }
constexpr auto d = baz (); // { dg-error "immediate evaluation returns
address of immediate function 'consteval int foo\\(\\)'" }
constexpr auto e = qux ();
constexpr auto f = quux ();
--- gcc/testsuite/g++.dg/cpp2a/consteval24.C.jj 2021-10-19 14:32:51.858019368
+0200
+++ gcc/testsuite/g++.dg/cpp2a/consteval24.C 2021-10-19 14:49:11.618177303
+0200
@@ -0,0 +1,30 @@
+// PR c++/102753
+// { dg-do compile { target c++20 } }
+
+struct S {
+ constexpr S () : s (0) {}
+ consteval int foo () { return 1; }
+ virtual consteval int bar () { return 2; }
+ int s;
+};
+
+consteval int foo () { return 42; }
+consteval auto baz () { return foo; }
+consteval auto qux () { return &S::foo; }
+consteval auto corge () { return &S::bar; }
+
+consteval int
+bar ()
+{
+ S s;
+ constexpr auto fn1 = foo; // { dg-error "immediate evaluation
returns address of immediate function" }
+ constexpr auto fn2 = &foo; // { dg-error "immediate evaluation
returns address of immediate function" }
+ constexpr auto fn3 = &S::foo; // { dg-error "immediate
evaluation returns address of immediate function" }
+ constexpr auto fn4 = &S::bar; // { dg-error "immediate
evaluation returns address of immediate function" }
+ constexpr auto fn5 = baz (); // { dg-error "immediate evaluation
returns address of immediate function" }
+ constexpr auto fn6 = qux (); // { dg-error "immediate evaluation
returns address of immediate function" }
+ constexpr auto fn7 = corge (); // { dg-error "immediate evaluation
returns address of immediate function" }
+ return fn1 () + fn2 () + (s.*fn3) () + (s.*fn4) () + fn5 () + (s.*fn6) () +
(s.*fn7) ();
+}
+
+auto a = bar ();
--- gcc/testsuite/g++.dg/cpp23/consteval-if12.C.jj 2021-10-19
14:54:05.123023731 +0200
+++ gcc/testsuite/g++.dg/cpp23/consteval-if12.C 2021-10-19 14:55:29.026844039
+0200
@@ -0,0 +1,34 @@
+// PR c++/102753
+// { dg-do compile { target c++20 } }
+// { dg-options "" }
+
+struct S {
+ constexpr S () : s (0) {}
+ consteval int foo () { return 1; }
+ virtual consteval int bar () { return 2; }
+ int s;
+};
+
+consteval int foo () { return 42; }
+consteval auto baz () { return foo; }
+consteval auto qux () { return &S::foo; }
+consteval auto corge () { return &S::bar; }
+
+constexpr int
+bar ()
+{
+ S s;
+ if consteval { // { dg-warning "'if consteval' only
available with" "" { target c++20_only } }
+ constexpr auto fn1 = foo; // { dg-error "immediate evaluation
returns address of immediate function" }
+ constexpr auto fn2 = &foo; // { dg-error "immediate evaluation
returns address of immediate function" }
+ constexpr auto fn3 = &S::foo; // { dg-error "immediate evaluation
returns address of immediate function" }
+ constexpr auto fn4 = &S::bar; // { dg-error "immediate evaluation
returns address of immediate function" }
+ constexpr auto fn5 = baz (); // { dg-error "immediate evaluation
returns address of immediate function" }
+ constexpr auto fn6 = qux (); // { dg-error "immediate evaluation
returns address of immediate function" }
+ constexpr auto fn7 = corge (); // { dg-error "immediate evaluation
returns address of immediate function" }
+ return fn1 () + fn2 () + (s.*fn3) () + (s.*fn4) () + fn5 () + (s.*fn6) ()
+ (s.*fn7) ();
+ }
+ return 0;
+}
+
+auto a = bar ();
Jakub
