https://gcc.gnu.org/g:f60570b26446781c0205981804f6aa4ff1708b12
commit r15-9226-gf60570b26446781c0205981804f6aa4ff1708b12
Author: Patrick Palka <ppa...@redhat.com>
Date: Sat Apr 5 15:22:48 2025 -0400
c++: harmless use of 'this' rejected despite P2280R4 [PR118249]
Here the implicit use of 'this' in inner.size() template argument was
being rejected despite P2280R4 relaxations, due to the special *this
handling in the INDIRECT_REF case of potential_constant_expression_1.
This handling was originally added by r196737 as part of fixing PR56481,
and it seems obsolete especially in light of P2280R4. There doesn't
seem to be a good reason that we need to handle *this specially from
other dereferences.
This patch therefore removes this special handling. As a side benefit
we now correctly reject some *reinterpret_cast<...>(...) constructs
earlier, via p_c_e_1 rather than via constexpr evaluation (because the
removed STRIP_NOPS step meant we'd overlook such casts), which causes a
couple of diagnostic changes (for the better).
PR c++/118249
gcc/cp/ChangeLog:
* constexpr.cc (potential_constant_expression_1)
<case INDIRECT_REF>: Remove obsolete *this handling.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/constexpr-reinterpret2.C: Expect error at
call site of the non-constexpr functions.
* g++.dg/cpp23/constexpr-nonlit12.C: Likewise.
* g++.dg/cpp0x/constexpr-ref14.C: New test.
Reviewed-by: Jason Merrill <ja...@redhat.com>
Diff:
---
gcc/cp/constexpr.cc | 17 +----------------
gcc/testsuite/g++.dg/cpp0x/constexpr-ref14.C | 21 +++++++++++++++++++++
gcc/testsuite/g++.dg/cpp0x/constexpr-reinterpret2.C | 4 ++--
gcc/testsuite/g++.dg/cpp23/constexpr-nonlit12.C | 2 +-
4 files changed, 25 insertions(+), 19 deletions(-)
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 9a57f4865e0f..37ea65cb6550 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -10279,22 +10279,7 @@ potential_constant_expression_1 (tree t, bool
want_rval, bool strict, bool now,
return true;
case INDIRECT_REF:
- {
- tree x = TREE_OPERAND (t, 0);
- STRIP_NOPS (x);
- if (is_this_parameter (x) && !is_capture_proxy (x))
- {
- if (now || !var_in_maybe_constexpr_fn (x))
- {
- if (flags & tf_error)
- constexpr_error (loc, fundef_p, "use of %<this%> in a "
- "constant expression");
- return false;
- }
- return true;
- }
- return RECUR (x, rval);
- }
+ return RECUR (TREE_OPERAND (t, 0), rval);
case STATEMENT_LIST:
for (tree stmt : tsi_range (t))
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-ref14.C
b/gcc/testsuite/g++.dg/cpp0x/constexpr-ref14.C
new file mode 100644
index 000000000000..f201afbd81f9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-ref14.C
@@ -0,0 +1,21 @@
+// PR c++/118249
+// { dg-do compile { target c++11 } }
+
+template <int I>
+void f() { }
+
+template <int N>
+struct array {
+ constexpr int size() const { return N; }
+};
+
+extern array<10>& outer;
+
+struct C {
+ array<10> inner;
+
+ void g() {
+ f<outer.size()>(); // OK
+ f<inner.size()>(); // was error: use of 'this' in a constant expression
+ }
+};
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-reinterpret2.C
b/gcc/testsuite/g++.dg/cpp0x/constexpr-reinterpret2.C
index 1bc2a8f30122..52328bc4ff55 100644
--- a/gcc/testsuite/g++.dg/cpp0x/constexpr-reinterpret2.C
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-reinterpret2.C
@@ -17,5 +17,5 @@ bar ()
return ((void **) &s)[0]; // { dg-error "reinterpret_cast" }
}
-constexpr auto x = foo ();
-constexpr auto y = bar ();
+constexpr auto x = foo (); // { dg-error "called in a constant expression" }
+constexpr auto y = bar (); // { dg-error "called in a constant expression" }
diff --git a/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit12.C
b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit12.C
index 8f003b801907..b104b16784fc 100644
--- a/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit12.C
+++ b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit12.C
@@ -19,6 +19,6 @@ void
g ()
{
constexpr int i = 42;
- constexpr auto a1 = fn0 (&i);
+ constexpr auto a1 = fn0 (&i); // { dg-error "called in a constant
expression" }
constexpr auto a2 = fn1 (i); // { dg-error "called in a constant expression"
}
}
