On Thu, Apr 04, 2024 at 05:28:22PM -0400, Jason Merrill wrote:
> On 4/4/24 14:43, Marek Polacek wrote:
> > On Wed, Apr 03, 2024 at 01:14:46PM -0400, Jason Merrill wrote:
> > > On 4/2/24 13:52, Marek Polacek wrote:
> > > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/13?
> > > >
> > > > -- >8 --
> > > > We evaluate constexpr functions on the original, pre-genericization
> > > > bodies.
> > > > That means that the function body we're evaluating will not have gone
> > > > through cp_genericize_r's "Map block scope extern declarations to
> > > > visible
> > > > declarations with the same name and type in outer scopes if any". Here:
> > > >
> > > > constexpr bool bar() { return true; } // #1
> > > > constexpr bool foo() {
> > > > constexpr bool bar(void); // #2
> > > > return bar();
> > > > }
> > > >
> > > > it means that we:
> > > > 1) register_constexpr_fundef (#1)
> > > > 2) cp_genericize (#1)
> > > > nothing interesting happens
> > > > 3) register_constexpr_fundef (foo)
> > > > does copy_fn, so we have two copies of the BIND_EXPR
> > > > 4) cp_genericize (foo)
> > > > this remaps #2 to #1, but only on one copy of the BIND_EXPR
> > > > 5) retrieve_constexpr_fundef (foo)
> > > > we find it, no problem
> > > > 6) retrieve_constexpr_fundef (#2)
> > > > and here #2 isn't found in constexpr_fundef_table, because
> > > > we're working on the BIND_EXPR copy where #2 wasn't mapped to #1
> > > > so we fail. We've only registered #1.
> > > >
> > > > It should work to use DECL_LOCAL_DECL_ALIAS (which used to be
> > > > extern_decl_map). We evaluate constexpr functions on pre-cp_fold
> > > > bodies to avoid diagnostic problems, but the remapping I'm proposing
> > > > should not interfere with diagnostics.
> > > >
> > > > This is not a problem for a global scope redeclaration; there we go
> > > > through duplicate_decls which keeps the DECL_UID:
> > > > DECL_UID (olddecl) = olddecl_uid;
> > > > and DECL_UID is what constexpr_fundef_hasher::hash uses.
> > > >
> > > > PR c++/111132
> > > >
> > > > gcc/cp/ChangeLog:
> > > >
> > > > * constexpr.cc (get_function_named_in_call): If there's
> > > > a DECL_LOCAL_DECL_ALIAS, use it.
> > >
> > > Perhaps this function should use cp_get_fndecl_from_callee, and this
> > > change
> > > should be made there instead?
> >
> > It doesn't seem that get_function_named_in_call can use
> > cp_get_fndecl_from_callee,
> > (or be replaced with cp_get_callee_fndecl_nofold). We can get e.g. a
> > CALL_EXPR
> > whose CALL_EXPR_FN is a TEMPLATE_ID_EXPR, and get_function_named_in_call
> > returns the TEMPLATE_ID_EXPR whereas cp_get_fndecl_from_callee would return
> > null:
> >
> > if (TREE_CODE (fn) == FUNCTION_DECL)
> > return fn;
> > tree type = TREE_TYPE (fn);
> > if (type == NULL_TREE || !INDIRECT_TYPE_P (type))
> > return NULL_TREE;
>
> Why couldn't this function use cp_get_fndecl_from_callee and return the
> original argument if that function returns null?
It could. (The lambda below could have been a goto but either should be fine.)
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/13?
-- >8 --
We evaluate constexpr functions on the original, pre-genericization bodies.
That means that the function body we're evaluating will not have gone
through cp_genericize_r's "Map block scope extern declarations to visible
declarations with the same name and type in outer scopes if any". Here:
constexpr bool bar() { return true; } // #1
constexpr bool foo() {
constexpr bool bar(void); // #2
return bar();
}
it means that we:
1) register_constexpr_fundef (#1)
2) cp_genericize (#1)
nothing interesting happens
3) register_constexpr_fundef (foo)
does copy_fn, so we have two copies of the BIND_EXPR
4) cp_genericize (foo)
this remaps #2 to #1, but only on one copy of the BIND_EXPR
5) retrieve_constexpr_fundef (foo)
we find it, no problem
6) retrieve_constexpr_fundef (#2)
and here #2 isn't found in constexpr_fundef_table, because
we're working on the BIND_EXPR copy where #2 wasn't mapped to #1
so we fail. We've only registered #1.
It should work to use DECL_LOCAL_DECL_ALIAS (which used to be
extern_decl_map). We evaluate constexpr functions on pre-cp_fold
bodies to avoid diagnostic problems, but the remapping I'm proposing
should not interfere with diagnostics.
This is not a problem for a global scope redeclaration; there we go
through duplicate_decls which keeps the DECL_UID:
DECL_UID (olddecl) = olddecl_uid;
and DECL_UID is what constexpr_fundef_hasher::hash uses.
PR c++/111132
gcc/cp/ChangeLog:
* constexpr.cc (get_function_named_in_call): Use
cp_get_fndecl_from_callee.
* cvt.cc (cp_get_fndecl_from_callee): If there's a
DECL_LOCAL_DECL_ALIAS, use it.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/constexpr-redeclaration3.C: New test.
* g++.dg/cpp0x/constexpr-redeclaration4.C: New test.
---
gcc/cp/constexpr.cc | 10 ++++------
gcc/cp/cvt.cc | 18 ++++++++++++++++--
.../g++.dg/cpp0x/constexpr-redeclaration3.C | 13 +++++++++++++
.../g++.dg/cpp0x/constexpr-redeclaration4.C | 14 ++++++++++++++
4 files changed, 47 insertions(+), 8 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-redeclaration3.C
create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-redeclaration4.C
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index fa346fe01c9..410ccdf597f 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -702,16 +702,14 @@ build_constexpr_constructor_member_initializers (tree
type, tree body)
/* We have an expression tree T that represents a call, either CALL_EXPR
or AGGR_INIT_EXPR. If the call is lexically to a named function,
- retrun the _DECL for that function. */
+ return the _DECL for that function. */
static tree
get_function_named_in_call (tree t)
{
- tree fun = cp_get_callee (t);
- if (fun && TREE_CODE (fun) == ADDR_EXPR
- && TREE_CODE (TREE_OPERAND (fun, 0)) == FUNCTION_DECL)
- fun = TREE_OPERAND (fun, 0);
- return fun;
+ tree callee = cp_get_callee (t);
+ tree fun = cp_get_fndecl_from_callee (callee, /*fold*/false);
+ return fun ? fun : callee;
}
/* Subroutine of check_constexpr_fundef. BODY is the body of a function
diff --git a/gcc/cp/cvt.cc b/gcc/cp/cvt.cc
index cbed847b343..db086c017e8 100644
--- a/gcc/cp/cvt.cc
+++ b/gcc/cp/cvt.cc
@@ -1001,8 +1001,22 @@ cp_get_fndecl_from_callee (tree fn, bool fold /* = true
*/)
{
if (fn == NULL_TREE)
return fn;
+
+ /* We evaluate constexpr functions on the original, pre-genericization
+ bodies. So block-scope extern declarations have not been mapped to
+ declarations in outer scopes. Use the namespace-scope declaration,
+ if any, so that retrieve_constexpr_fundef can find it (PR111132). */
+ auto fn_or_local_alias = [] (tree f)
+ {
+ if (DECL_LOCAL_DECL_P (f))
+ if (tree alias = DECL_LOCAL_DECL_ALIAS (f))
+ if (alias != error_mark_node)
+ return alias;
+ return f;
+ };
+
if (TREE_CODE (fn) == FUNCTION_DECL)
- return fn;
+ return fn_or_local_alias (fn);
tree type = TREE_TYPE (fn);
if (type == NULL_TREE || !INDIRECT_TYPE_P (type))
return NULL_TREE;
@@ -1013,7 +1027,7 @@ cp_get_fndecl_from_callee (tree fn, bool fold /* = true
*/)
|| TREE_CODE (fn) == FDESC_EXPR)
fn = TREE_OPERAND (fn, 0);
if (TREE_CODE (fn) == FUNCTION_DECL)
- return fn;
+ return fn_or_local_alias (fn);
return NULL_TREE;
}
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-redeclaration3.C
b/gcc/testsuite/g++.dg/cpp0x/constexpr-redeclaration3.C
new file mode 100644
index 00000000000..2b41b456fc3
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-redeclaration3.C
@@ -0,0 +1,13 @@
+// PR c++/111132
+// { dg-do compile { target c++11 } }
+
+constexpr bool bar(void) {
+ return true;
+}
+
+constexpr bool foo() {
+ constexpr bool bar(void);
+ return bar();
+}
+
+static_assert(foo(), "");
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-redeclaration4.C
b/gcc/testsuite/g++.dg/cpp0x/constexpr-redeclaration4.C
new file mode 100644
index 00000000000..c58247218c6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-redeclaration4.C
@@ -0,0 +1,14 @@
+// PR c++/111132
+// { dg-do compile { target c++11 } }
+
+constexpr bool bar(void) {
+ return true;
+}
+
+constexpr bool bar(void);
+
+constexpr bool foo() {
+ return bar();
+}
+
+static_assert(foo(), "");
base-commit: 27b6d081f68528435066be2234c7329e31e0e84f
--
2.44.0
