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Incorrect order of base-class initializers in class template [GH #302] #318

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21 changes: 21 additions & 0 deletions src/Changes
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Original file line number Diff line number Diff line change
@@ -1,5 +1,26 @@
Version 7.1

10/16/26 [GH #302]
Incorrect order of base-class initializers in class template

Previously, in the IL for prototype instantiations of class templates,
base-class mem-initializers with non-type template arguments could appear after
the initializers for other base classes. Such initializers are now recorded in
base-class declaration order when the base class can be identified.
Initializers for base classes that cannot yet be identified now retain their
source order relative to the next initializer for an identified nonvirtual
direct base class. For example, with --c++11:

template<int> struct A { };
struct B { };
template<int N> struct C : A<N>, B {
C() : A<N>(), B() { } // Previously recorded as "B(), A<N>()".
C(int) : A<+N>(), B() { } // Previously recorded as "B(), A<+N>()".
};

Both initializer lists are now recorded in the order shown.


10/16/26 [GH #229]
Improper handling of "if constexpr" substatements

Expand Down
72 changes: 68 additions & 4 deletions src/decl_inits.c
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Original file line number Diff line number Diff line change
Expand Up @@ -7508,6 +7508,14 @@ typedef struct a_ctor_init_block {
a_boolean out_of_order_diag_issued;
/* TRUE if a diagnostic has been issued about
mem-initializers not matching declaration order. */
a_constructor_init_ptr
first_pending_unresolved_base_init;
/* First pending constructor init for a base class
not matched with the base class list. These entries
occupy the tail of direct_list until the next
mem-initializer for a matched nonvirtual direct
base class is scanned. NULL if no entries are
pending. */
a_boolean pack_expansion_context_started;
/* TRUE if begin_potential_pack_expansion_context has
been called for a mem-initializer, and elements
Expand Down Expand Up @@ -7597,10 +7605,61 @@ template containing the ctor-initializer is instantiated.
cibp->end_of_direct_list->next = new_cip;
} /* if */
cibp->end_of_direct_list = new_cip;
if (cibp->first_pending_unresolved_base_init == NULL) {
cibp->first_pending_unresolved_base_init = new_cip;
} /* if */
return new_cip;
} /* add_new_unresolved_base_ctor_init */


static void move_pending_unresolved_base_inits(
a_ctor_init_block *cibp,
a_constructor_init_ptr explicit_cip)
/*
cibp tracks the constructor init entries for the constructor being defined.
If it has pending entries for unresolved base classes, move them from the tail
of direct_list to immediately before explicit_cip and clear the pending state.
explicit_cip is the existing init entry for the matched nonvirtual direct base
class whose mem-initializer is being scanned. This preserves the source order
of the unresolved mem-initializers relative to that mem-initializer.
*/
{
a_constructor_init_ptr first_pending =
cibp->first_pending_unresolved_base_init;
a_constructor_init_ptr last_pending = cibp->end_of_direct_list;

if (first_pending != NULL) {
/* Find the predecessors of the pending tail and explicit_cip. */
a_constructor_init_ptr prev_of_pending = NULL, prev_of_explicit = NULL;

check_assertion(last_pending != NULL && last_pending->next == NULL);
for (a_constructor_init_ptr cip = cibp->direct_list, prev_cip = NULL;
cip != NULL;
prev_cip = cip, cip = cip->next) {
if (cip == first_pending) {
prev_of_pending = prev_cip;
break;
} /* if */
if (cip == explicit_cip) prev_of_explicit = prev_cip;
} /* for */
check_assertion(prev_of_pending != NULL &&
(explicit_cip == cibp->direct_list ||
prev_of_explicit != NULL));
/* Remove the pending entries from the end of the list and splice them
before explicit_cip. */
prev_of_pending->next = NULL;
cibp->end_of_direct_list = prev_of_pending;
last_pending->next = explicit_cip;
if (prev_of_explicit == NULL) {
cibp->direct_list = first_pending;
} else {
prev_of_explicit->next = first_pending;
} /* if */
cibp->first_pending_unresolved_base_init = NULL;
} /* if */
} /* move_pending_unresolved_base_inits */


static a_symbol_ptr look_up_mem_initializer_id(void)
/*
The current token is a (generalized) identifier of a mem-initializer-id (which
Expand Down Expand Up @@ -7967,7 +8026,8 @@ all known yet; it is left unchanged otherwise.
that only direct and virtual base classes can be specified. */
bcp = base_classes_of(class_type);
for (; bcp != NULL; bcp = bcp->next) {
if (same_entities(bcp->type, init_type)) {
if (identical_types_full(bcp->type, init_type,
ITF_EXACT_DECLTYPE_EXPR_MATCH_REQUIRED)) {
if (bcp->direct || bcp->is_virtual) {
if (found_bcp == NULL) {
found_bcp = bcp;
Expand Down Expand Up @@ -8036,10 +8096,13 @@ all known yet; it is left unchanged otherwise.
for (; new_cip != NULL; new_cip = new_cip->next) {
if (new_cip->variant.base_class == bcp) break;
} /* for */
if (new_cip == NULL && prototype_instantiation) {
new_cip = add_new_unresolved_base_ctor_init(cibp,init_type);
}
check_assertion(new_cip != NULL);
if (!bcp->is_virtual) {
/* Place pending unresolved base initializers before this matched
direct-base initializer, following their relative order in the
ctor-initializer list. */
move_pending_unresolved_base_inits(cibp, new_cip);
} /* if */
/* new_cip was initially marked as compiler-generated. Reset the
flag now that it's appeared explicitly in the ctor-initializer
list. */
Expand Down Expand Up @@ -9301,6 +9364,7 @@ initialized. These are addressed in the course of the processing.
cib.pending_decltype_pos = null_source_position;
cib.has_explicit_init = FALSE;
cib.out_of_order_diag_issued = FALSE;
cib.first_pending_unresolved_base_init = NULL;
cib.pack_expansion_context_started = FALSE;
if (user_defined && curr_token == tok_colon) {
/* User-specified initializers are present. */
Expand Down
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