On Wed, Jul 09, 2025 at 06:45:41PM -0400, Jason Merrill wrote:
+ && reduced_constant_expression_p (val))
And a value doesn't need to be constant to be printable, we should be able
to print it unconditionally.
Sure, the question is if printing non-constant value is better for users.
The change to do unconditionally the %qE results in
/usr/src/gcc/gcc/testsuite/g++.dg/cpp26/constexpr-eh12.C:71:49: error: uncaught
exception '(E*)(& heap )'
while previously it was
/usr/src/gcc/gcc/testsuite/g++.dg/cpp26/constexpr-eh12.C:71:49: error: uncaught
exception of type 'E*'
I've kept the conditional for now but if you really want that change, can
remove it
in the 2 spots and tweak constexpr-eh12.C test's expectations.
Is there a reason not to add it to heap_vars here?
In the earlier patch I had:
+ case CXA_ALLOCATE_EXCEPTION:
...
+ tree var = cxa_allocate_exception (loc, type, size_zero_node);
+ ctx->global->heap_vars.safe_push (var);
+ ctx->global->put_value (var, NULL_TREE);
vs.
+ case CXA_BAD_CAST:
+ case CXA_BAD_TYPEID:
+ case CXA_THROW_BAD_ARRAY_NEW_LENGTH:
...
+ tree var = cxa_allocate_exception (loc, type, size_one_node);
+ tree ctor
+ = build_special_member_call (var, complete_ctor_identifier,
+ NULL, type, LOOKUP_NORMAL,
+ ctx->quiet ? tf_none
+ : tf_warning_or_error);
+ if (ctor == error_mark_node)
+ {
+ *non_constant_p = true;
+ return call;
+ }
+ ctx->global->heap_vars.safe_push (var);
and so it wasn't added to heap_vars if build_special_member_call failed.
But thinking about it now, we really don't care about what is in heap_vars
if *non_constant_p, so I've made the change.
The rest incorporated into the following version of the patch, passes
GXX_TESTSUITE_STDS=98,11,14,17,20,23,26 make check-g++
RUNTESTFLAGS="--target_board=unix/-fpie dg.exp='constexpr-eh* constexpr-asm-5.C
static_assert1.C feat-cxx26.C constexpr-throw.C constexpr-84192.C constexpr-dynamic*.C
consteval34.C constexpr-new27.C consteval-memfn1.C constexpr-typeid5.C
constexpr-ellipsis*'"
so far.
2025-07-10 Jakub Jelinek <ja...@redhat.com>
PR c++/117785
gcc/c-family/
* c-cppbuiltin.cc (c_cpp_builtins): Predefine
__cpp_constexpr_exceptions=202411L for C++26.
gcc/cp/
* constexpr.cc: Implement C++26 P3068R5 - constexpr exceptions.
(class constexpr_global_ctx): Add caught_exceptions and
uncaught_exceptions members.
(constexpr_global_ctx::constexpr_global_ctx): Initialize
uncaught_exceptions.
(returns, breaks, continues, switches): Move earlier.
(throws): New function.
(exception_what_str, diagnose_std_terminate,
diagnose_uncaught_exception): New functions.
(enum cxa_builtin): New type.
(cxx_cxa_builtin_fn_p, cxx_eval_cxa_builtin_fn): New functions.
(cxx_eval_builtin_function_call): Add jump_target argument. Call
cxx_eval_cxa_builtin_fn for __builtin_eh_ptr_adjust_ref. Adjust
cxx_eval_constant_expression calls, if it results in jmp_target,
set *jump_target to it and return.
(cxx_bind_parameters_in_call): Add jump_target argument. Pass
it through to cxx_eval_constant_expression. If it sets *jump_target,
break.
(fold_operand): Adjust cxx_eval_constant_expression caller.
(cxx_eval_assert): Likewise. If it set jmp_target, return true.
(cxx_eval_internal_function): Add jump_target argument. Pass it
through to cxx_eval_constant_expression. Return early if
*jump_target after recursing on args.
(cxx_eval_dynamic_cast_fn): Likewise. Don't set reference_p for
C++26 with -fexceptions.
(cxx_eval_thunk_call): Add jump_target argument. Pass it through
to cxx_eval_constant_expression.
(cxx_set_object_constness): Likewise. Don't set TREE_READONLY if
throws (jump_target).
(cxx_eval_call_expression): Add jump_target argument. Pass it
through to cxx_eval_internal_function, cxx_eval_builtin_function_call,
cxx_eval_thunk_call, cxx_eval_dynamic_cast_fn and
cxx_set_object_constness. Pass it through also
cxx_eval_constant_expression on arguments, cxx_bind_parameters_in_call
and cxx_fold_indirect_ref and for those cases return early if
*jump_target. Call cxx_eval_cxa_builtin_fn for cxx_cxa_builtin_fn_p
functions. For cxx_eval_constant_expression on body, pass address of
cleared jmp_target automatic variable, if it throws propagate to
*jump_target and make it non-cacheable. For C++26 don't diagnose
calls to non-constexpr functions before cxx_bind_parameters_in_call
could report some argument throwing an exception.
(cxx_eval_unary_expression): Add jump_target argument. Pass it
through to cxx_eval_constant_expression and return early if
*jump_target after the call.
(cxx_fold_pointer_plus_expression): Likewise.
(cxx_eval_binary_expression): Likewise and similarly for
cxx_fold_pointer_plus_expression call.
(cxx_eval_conditional_expression): Pass jump_target to
cxx_eval_constant_expression on first operand and return early if
*jump_target after the call.
(cxx_eval_vector_conditional_expression): Add jump_target argument.
Pass it through to cxx_eval_constant_expression for all 3 arguments
and return early if *jump_target after any of those calls.
(get_array_or_vector_nelts): Add jump_target argument. Pass it
through to cxx_eval_constant_expression.
(eval_and_check_array_index): Add jump_target argument. Pass it
through to cxx_eval_constant_expression calls and return early after
each of them if *jump_target.
(cxx_eval_array_reference): Likewise.
(cxx_eval_component_reference): Likewise.
(cxx_eval_bit_field_ref): Likewise.
(cxx_eval_bit_cast): Likewise. Assert CHECKING_P call doesn't
throw or return.
(cxx_eval_logical_expression): Add jump_target argument. Pass it
through to cxx_eval_constant_expression calls and return early after
each of them if *jump_target.
(cxx_eval_bare_aggregate): Likewise.
(cxx_eval_vec_init_1): Add jump_target argument. Pass it through
to cxx_eval_bare_aggregate and recursive call. Pass it through
to get_array_or_vector_nelts and cxx_eval_constant_expression
and return early after it if *jump_target.
(cxx_eval_vec_init): Add jump_target argument. Pass it through
to cxx_eval_constant_expression and cxx_eval_vec_init_1.
(cxx_union_active_member): Add jump_target argument. Pass it
through to cxx_eval_constant_expression and return early after it
if *jump_target.
(cxx_fold_indirect_ref_1): Add jump_target argument. Pass it
through to cxx_union_active_member and recursive calls.
(cxx_eval_indirect_ref): Add jump_target argument. Pass it through
to cxx_fold_indirect_ref_1 calls and to recursive call, in which
case return early after it if *jump_target.
(cxx_fold_indirect_ref): Add jump_target argument. Pass it through
to cxx_fold_indirect_ref and cxx_eval_constant_expression calls and
return early after those if *jump_target.
(cxx_eval_trinary_expression): Add jump_target argument. Pass it
through to cxx_eval_constant_expression calls and return early after
those if *jump_target.
(cxx_eval_store_expression): Add jump_target argument. Pass it
through to cxx_eval_constant_expression and eval_and_check_array_index
calls and return early after those if *jump_target.
(cxx_eval_increment_expression): Add jump_target argument. Pass it
through to cxx_eval_constant_expression calls and return early after
those if *jump_target.
(label_matches): Handle VAR_DECL case.
(cxx_eval_statement_list): Remove local_target variable and
!jump_target handling. Handle throws (jump_target) like returns or
breaks.
(cxx_eval_loop_expr): Remove local_target variable and !jump_target
handling. Pass it through to cxx_eval_constant_expression. Handle
throws (jump_target) like returns.
(cxx_eval_switch_expr): Pass jump_target through to
cxx_eval_constant_expression on cond, return early after it if
*jump_target.
(build_new_constexpr_heap_type): Add jump_target argument. Pass it
through to cxx_eval_constant_expression calls, return early after
those if *jump_target.
(merge_jump_target): New function.
(cxx_eval_constant_expression): Make jump_target argument no longer
defaulted, don't test jump_target for NULL. Pass jump_target
through to recursive calls, cxx_eval_call_expression,
cxx_eval_store_expression, cxx_eval_indirect_ref,
cxx_eval_unary_expression, cxx_eval_binary_expression,
cxx_eval_logical_expression, cxx_eval_array_reference,
cxx_eval_component_reference, cxx_eval_bit_field_ref,
cxx_eval_vector_conditional_expression, cxx_eval_bare_aggregate,
cxx_eval_vec_init, cxx_eval_trinary_expression, cxx_fold_indirect_ref,
build_new_constexpr_heap_type, cxx_eval_increment_expression,
cxx_eval_bit_cast and return earlyu after some of those if
*jump_target as needed.
(cxx_eval_constant_expression) <case TARGET_EXPR>: For C++26 push
also CLEANUP_EH_ONLY cleanups, with NULL_TREE marker after them.
(cxx_eval_constant_expression) <case RETURN_EXPR>: Don't override
*jump_target if throws (jump_target).
(cxx_eval_constant_expression) <case TRY_CATCH_EXPR, case TRY_BLOCK,
case MUST_NOT_THROW_EXPR, case TRY_FINALLY_EXPR, case CLEANUP_STMT>:
Handle C++26 constant expressions.
(cxx_eval_constant_expression) <case CLEANUP_POINT_EXPR>: For C++26
with throws (jump_target) evaluate the CLEANUP_EH_ONLY cleanups as
well, and if not throws (jump_target) skip those. Set *jump_target
if some of the cleanups threw.
(cxx_eval_constant_expression) <case THROW_EXPR>: Recurse on operand
for C++26.
(cxx_eval_outermost_constant_expr): Diagnose uncaught exceptions both
from main expression and cleanups, diagnose also
break/continue/returns from the main expression. Handle
CLEANUP_EH_ONLY cleanup markers. Don't diagnose mutable poison stuff
if non_constant_p. Use different diagnostics for non-deleted heap
allocations if they were allocated by __cxa_allocate_exception.
(callee_might_throw): New function.
(struct check_for_return_continue_data): Add could_throw field.
(check_for_return_continue): Handle AGGR_INIT_EXPR and CALL_EXPR and
set d->could_throw if they could throw.
(potential_constant_expression_1): For CALL_EXPR allow
cxx_dynamic_cast_fn_p calls. For C++26 set *jump_target to void_node
for calls that could throw. For C++26 if call to non-constexpr call
is seen, try to evaluate arguments first and if they could throw,
don't diagnose call to non-constexpr function nor return false.
Adjust check_for_return_continue_data initializers and set
*jump_target to void_node if data.could_throw_p. For C++26 recurse on
THROW_EXPR argument. Add comment explaining TRY_BLOCK handling with
C++26 exceptions. Handle throws like returns in some cases.
* cp-tree.h (MUST_NOT_THROW_NOEXCEPT_P, MUST_NOT_THROW_THROW_P,
MUST_NOT_THROW_CATCH_P, DECL_EXCEPTION_REFCOUNT): Define.
(DECL_LOCAL_DECL_P): Fix comment typo, VARIABLE_DECL -> VAR_DECL.
(enum cp_built_in_function): Add CP_BUILT_IN_EH_PTR_ADJUST_REF,
(handler_match_for_exception_type): Declare.
* call.cc (handler_match_for_exception_type): New function.
* except.cc (initialize_handler_parm): Set MUST_NOT_THROW_CATCH_P
on newly created MUST_NOT_THROW_EXPR.
(begin_eh_spec_block): Set MUST_NOT_THROW_NOEXCEPT_P.
(wrap_cleanups_r): Set MUST_NOT_THROW_THROW_P.
(build_throw): Add another TARGET_EXPR whose scope spans
until after the __cxa_throw call and copy pointer value from ptr
to it and use it in __cxa_throw argument.
* tree.cc (builtin_valid_in_constant_expr_p): Handle
CP_BUILT_IN_EH_PTR_ADJUST_REF.
* decl.cc (cxx_init_decl_processing): Initialize
__builtin_eh_ptr_adjust_ref FE builtin.
* pt.cc (tsubst_stmt) <case MUST_NOT_THROW_EXPR>: Copy the
MUST_NOT_THROW_NOEXCEPT_P, MUST_NOT_THROW_THROW_P and
MUST_NOT_THROW_CATCH_P flags.
* cp-gimplify.cc (cp_gimplify_expr) <case CALL_EXPR>: Error on
non-folded CP_BUILT_IN_EH_PTR_ADJUST_REF calls.
gcc/testsuite/
* g++.dg/cpp0x/constexpr-ellipsis2.C: Expect different diagnostics for
C++26.
* g++.dg/cpp0x/constexpr-throw.C: Likewise.
* g++.dg/cpp1y/constexpr-84192.C: Expect different diagnostics.
* g++.dg/cpp1y/constexpr-throw.C: Expect different diagnostics for
C++26.
* g++.dg/cpp1z/constexpr-asm-5.C: Likewise.
* g++.dg/cpp26/constexpr-eh1.C: New test.
* g++.dg/cpp26/constexpr-eh2.C: New test.
* g++.dg/cpp26/constexpr-eh3.C: New test.
* g++.dg/cpp26/constexpr-eh4.C: New test.
* g++.dg/cpp26/constexpr-eh5.C: New test.
* g++.dg/cpp26/constexpr-eh6.C: New test.
* g++.dg/cpp26/constexpr-eh7.C: New test.
* g++.dg/cpp26/constexpr-eh8.C: New test.
* g++.dg/cpp26/constexpr-eh9.C: New test.
* g++.dg/cpp26/constexpr-eh10.C: New test.
* g++.dg/cpp26/constexpr-eh11.C: New test.
* g++.dg/cpp26/constexpr-eh12.C: New test.
* g++.dg/cpp26/constexpr-eh13.C: New test.
* g++.dg/cpp26/constexpr-eh14.C: New test.
* g++.dg/cpp26/constexpr-eh15.C: New test.
* g++.dg/cpp26/feat-cxx26.C: Change formatting in __cpp_pack_indexing
and __cpp_pp_embed test. Add __cpp_constexpr_exceptions test.
* g++.dg/cpp26/static_assert1.C: Expect different diagnostics for
C++26.
* g++.dg/cpp2a/consteval34.C: Likewise.
* g++.dg/cpp2a/consteval-memfn1.C: Likewise.
* g++.dg/cpp2a/constexpr-dynamic4.C: For C++26 add std::exception and
std::bad_cast definitions and expect different diagnostics.
* g++.dg/cpp2a/constexpr-dynamic6.C: Likewise.
* g++.dg/cpp2a/constexpr-dynamic7.C: Likewise.
* g++.dg/cpp2a/constexpr-dynamic8.C: Likewise.
* g++.dg/cpp2a/constexpr-dynamic9.C: Likewise.
* g++.dg/cpp2a/constexpr-dynamic11.C: Likewise.
* g++.dg/cpp2a/constexpr-dynamic14.C: Likewise.
* g++.dg/cpp2a/constexpr-dynamic18.C: Likewise.
* g++.dg/cpp2a/constexpr-new27.C: New test.
* g++.dg/cpp2a/constexpr-typeid5.C: New test.
libstdc++-v3/
* include/bits/version.def (constexpr_exceptions): New.
* include/bits/version.h: Regenerate.
* libsupc++/exception (std::bad_exception::bad_exception): Add
_GLIBCXX26_CONSTEXPR.
(std::bad_exception::~bad_exception, std::bad_exception::what): For
C++26 add constexpr and define inline.
* libsupc++/exception.h (std::exception::exception,
std::exception::operator=): Add _GLIBCXX26_CONSTEXPR.
(std::exception::~exception, std::exception::what): For C++26 add
constexpr and define inline.
* libsupc++/exception_ptr.h (std::make_exception_ptr): Add
_GLIBCXX26_CONSTEXPR. For if consteval use just throw with
current_exception() in catch.
(std::exception_ptr::exception_ptr(void*)): For C++26 add constexpr
and define inline.
(std::exception_ptr::exception_ptr()): Add _GLIBCXX26_CONSTEXPR.
(std::exception_ptr::exception_ptr(const exception_ptr&)): Likewise.
Use __builtin_eh_ptr_adjust_ref if consteval and compiler has it
instead of _M_addref.
(std::exception_ptr::exception_ptr(nullptr_t)): Add
_GLIBCXX26_CONSTEXPR.
(std::exception_ptr::exception_ptr(exception_ptr&&)): Likewise.
(std::exception_ptr::operator=): Likewise.
(std::exception_ptr::~exception_ptr): Likewise. Use
__builtin_eh_ptr_adjust_ref if consteval and compiler has it
instead of _M_release.
(std::exception_ptr::swap): Add _GLIBCXX26_CONSTEXPR.
(std::exception_ptr::operator bool): Likewise.
(std::exception_ptr::operator==): Likewise.
* libsupc++/nested_exception.h
(std::nested_exception::nested_exception): Add _GLIBCXX26_CONSTEXPR.
(std::nested_exception::operator=): Likewise.
(std::nested_exception::~nested_exception): For C++26 add constexpr
and define inline.
(std::nested_exception::rethrow_if_nested): Add _GLIBCXX26_CONSTEXPR.
(std::nested_exception::nested_ptr): Likewise.
(std::_Nested_exception::_Nested_exception): Likewise.
(std::throw_with_nested, std::rethrow_if_nested): Likewise.
* libsupc++/new (std::bad_alloc::bad_alloc): Likewise.
(std::bad_alloc::operator=): Likewise.
(std::bad_alloc::~bad_alloc): For C++26 add constexpr and define
inline.
(std::bad_alloc::what): Likewise.
(std::bad_array_new_length::bad_array_new_length): Add
_GLIBCXX26_CONSTEXPR.
(std::bad_array_new_length::~bad_array_new_length): For C++26 add
constexpr and define inline.
(std::bad_array_new_length::what): Likewise.
* libsupc++/typeinfo (std::bad_cast::bad_cast): Add
_GLIBCXX26_CONSTEXPR.
(std::bad_cast::~bad_cast): For C++26 add constexpr and define inline.
(std::bad_cast::what): Likewise.
(std::bad_typeid::bad_typeid): Add _GLIBCXX26_CONSTEXPR.
(std::bad_typeid::~bad_typeid): For C++26 add constexpr and define
inline.
(std::bad_typeid::what): Likewise.
