On Tue, Jul 14, 2026 at 10:19:20AM -0400, Jason Merrill wrote:
@@ -9719,6 +9738,11 @@ cp_finish_decl (tree decl, tree init, bo
DECL_ATTRIBUTES (decl)))
omp_declare_variant_finalize (decl, attr);
+ /* [basic.stc.dynamic.deallocation]/3 - A deallocation function shall not
+ have a potentially throwing exception specification. */
+ if (cxx_dialect >= cxx29 && TREE_CODE (decl) == FUNCTION_DECL)
Let's move the cxx_dialect check into the new function.
Done.
@@ -20538,6 +20562,11 @@ finish_function (bool inline_p)
if (fndecl == NULL_TREE || fndecl == error_mark_node)
return error_mark_node;
+ /* [basic.stc.dynamic.deallocation]/3 - A deallocation function shall not
+ have a potentially throwing exception specification. */
+ if (cxx_dialect >= cxx29)
+ maybe_diagnose_deallocation_noexcept_false (fndecl);
It's surprising to check this here, where we're dealing with the end of a
function definition, as well as in the other two functions that deal with
forming the declaration.
Would it work to check in grokfndecl and not here nor in cp_finish_decl?
It works too (and doesn't emit the undesirable diagnostics in
cpp0x/dealloc2.C line 9 for C++29).
2026-07-14 Jakub Jelinek <[email protected]>
PR c++/125833
* cp-tree.h: Implement C++29 P3424R2 - Deallocation Functions with
Throwing Exception Specification Are Ill-formed.
(maybe_diagnose_deallocation_noexcept_false): Declare.
* decl.cc (maybe_diagnose_deallocation_noexcept_false): New function.
(grokfndecl): Call it.
* pt.cc (tsubst_function_decl): Likewise.
* g++.dg/cpp0x/dealloc2.C: Expect extra diagnostics in C++29.
* g++.dg/cpp29/dealloc1.C: New test.
--- gcc/cp/cp-tree.h.jj 2026-07-14 16:39:33.562964575 +0200
+++ gcc/cp/cp-tree.h 2026-07-14 16:40:07.619539955 +0200
@@ -7651,6 +7651,7 @@ extern tree start_decl (const
cp_decl
extern void start_decl_1 (tree, bool);
extern bool check_array_initializer (tree, tree, tree);
extern void omp_declare_variant_finalize (tree, tree);
+extern void maybe_diagnose_deallocation_noexcept_false (tree);
struct cp_decomp { tree decl; unsigned int count; };
extern void cp_finish_decl (tree, tree, bool, tree, int,
cp_decomp * = nullptr);
extern tree lookup_decomp_type (tree);
--- gcc/cp/decl.cc.jj 2026-07-14 16:39:33.563964563 +0200
+++ gcc/cp/decl.cc 2026-07-14 16:43:58.359663079 +0200
@@ -9430,6 +9430,26 @@ omp_declare_variant_finalize (tree decl,
}
}
+/* [basic.stc.dynamic.deallocation]/3 - A deallocation function shall not
+ have a potentially throwing exception specification. */
+
+void
+maybe_diagnose_deallocation_noexcept_false (tree decl)
+{
+ if (cxx_dialect >= cxx29
+ && DECL_NAME (decl)
+ && IDENTIFIER_NEWDEL_OP_P (DECL_NAME (decl))
+ && !IDENTIFIER_NEW_OP_P (DECL_NAME (decl)))
+ {
+ maybe_instantiate_noexcept (decl, tf_none);
+ tree spec = TYPE_RAISES_EXCEPTIONS (TREE_TYPE (decl));
+ if (spec && spec == noexcept_false_spec)
+ error_at (DECL_SOURCE_LOCATION (decl),
+ "deallocation function %qD declared possibly throwing",
+ decl);
+ }
+}
+
static void cp_maybe_mangle_decomp (tree, cp_decomp *);
/* Finish processing of a declaration;
@@ -12621,6 +12641,10 @@ grokfndecl (tree ctype,
}
}
+ /* [basic.stc.dynamic.deallocation]/3 - A deallocation function shall not
+ have a potentially throwing exception specification. */
+ maybe_diagnose_deallocation_noexcept_false (decl);
+
/* Caller will do the rest of this. */
if (check < 0)
{
--- gcc/cp/pt.cc.jj 2026-07-14 16:39:33.566964525 +0200
+++ gcc/cp/pt.cc 2026-07-14 16:44:15.358451136 +0200
@@ -15677,6 +15677,10 @@ tsubst_function_decl (tree t, tree args,
DECL_ATTRIBUTES (r)))
omp_declare_variant_finalize (r, attr);
+ /* [basic.stc.dynamic.deallocation]/3 - A deallocation function shall not
+ have a potentially throwing exception specification. */
+ maybe_diagnose_deallocation_noexcept_false (r);
+
return r;
}
--- gcc/testsuite/g++.dg/cpp0x/dealloc2.C.jj 2026-07-14 16:39:33.567964513 +0200
+++ gcc/testsuite/g++.dg/cpp0x/dealloc2.C 2026-07-14 16:54:36.950706126
+0200
@@ -3,6 +3,7 @@
struct A {};
void operator delete (void *, A);
void operator delete (void *, A) noexcept (false); // { dg-error "declaration
of 'void operator delete\\\(void\\\*, A\\\) noexcept \\\(false\\\)' has a different
exception specifier" }
+// { dg-error "deallocation function 'void operator delete\\\(void\\\*, A\\\)' declared
possibly throwing" "" { target c++29 } .-1 }
struct B {};
-void operator delete (void *, B) noexcept (false);
+void operator delete (void *, B) noexcept (false); // { dg-error "deallocation function
'void operator delete\\\(void\\\*, B\\\)' declared possibly throwing" "" { target
c++29 } }
void operator delete (void *, B); // { dg-error "declaration
of 'void operator delete\\\(void\\\*, B\\\) noexcept' has a different exception
specifier" }
--- gcc/testsuite/g++.dg/cpp29/dealloc1.C.jj 2026-07-14 16:40:07.659788894
+0200
+++ gcc/testsuite/g++.dg/cpp29/dealloc1.C 2026-07-14 16:40:07.659788894
+0200
@@ -0,0 +1,23 @@
+// P3424R2 - Deallocation Functions with Throwing Exception Specification Are
Ill-formed
+// { dg-do compile { target c++11 } }
+
+struct A {};
+struct B {};
+void operator delete (void *, A) noexcept (false); // { dg-error "deallocation function
'void operator delete\\\(void\\\*, A\\\)' declared possibly throwing" "" { target
c++29 } }
+void operator delete (void *, B) noexcept (false) {} // { dg-error "deallocation function
'void operator delete\\\(void\\\*, B\\\)' declared possibly throwing" "" { target
c++29 } }
+void operator delete[] (void *, A) noexcept (false); // { dg-error "deallocation function
'void operator delete \\\[\\\]\\\(void\\\*, A\\\)' declared possibly throwing" "" {
target c++29 } }
+void operator delete[] (void *, B) noexcept (false) {} // { dg-error "deallocation function
'void operator delete \\\[\\\]\\\(void\\\*, B\\\)' declared possibly throwing" "" {
target c++29 } }
+template <bool T>
+struct C {
+ static void operator delete (void *) noexcept (T); // { dg-error "deallocation function 'static
void C<T>::operator delete\\\(void\\\*\\\) \\\[with bool T = false\\\]' declared possibly
throwing" "" { target c++29 } }
+ static void operator delete[] (void *) noexcept (T); // { dg-error "deallocation function 'static
void C<T>::operator delete \\\[\\\]\\\(void\\\*\\\) \\\[with bool T = false\\\]' declared possibly
throwing" "" { target c++29 } }
+};
+template <bool T>
+struct D {
+ static void operator delete (void *) noexcept (T) {} // { dg-error "deallocation function 'static
void D<T>::operator delete\\\(void\\\*\\\) \\\[with bool T = false\\\]' declared possibly
throwing" "" { target c++29 } }
+ static void operator delete[] (void *) noexcept (T) {}// { dg-error "deallocation function
'static void D<T>::operator delete \\\[\\\]\\\(void\\\*\\\) \\\[with bool T = false\\\]' declared
possibly throwing" "" { target c++29 } }
+};
+C <false> a;
+C <true> b;
+D <false> c;
+D <true> d;
Jakub
