[gcc r16-7102] c, c++: Use c*_build_qualified_type instead of build_qualified_type from within build_type_attribute
Jakub Jelinek
jakub@gcc.gnu.org
Wed Jan 28 08:53:35 GMT 2026
https://gcc.gnu.org/g:3d2a91a3767982dde5a37abf45c12c08d4fdbf41
commit r16-7102-g3d2a91a3767982dde5a37abf45c12c08d4fdbf41
Author: Jakub Jelinek <jakub@redhat.com>
Date: Wed Jan 28 09:50:26 2026 +0100
c, c++: Use c*_build_qualified_type instead of build_qualified_type from within build_type_attribute_qual_variant [PR101312]
The following testcases ICE in various ways because of the interaction
between attributes and C/C++ c*_build_qualified_type behavior on array
types and how they affect TYPE_CANONICAL.
For array types, C/C++ moves qualifiers to the element type, but
when a cv qualified array build that way has an attribute applied to it,
we call build_type_attribute_qual_variant and that doesn't have that
handling and builds non-qualified version of the array type with qualified
element type and puts it as TYPE_CANONICAL of the type with attribute
which is a distinct type copy.
The following patch adds a langhook, so that even
build_type_attribute_qual_variant uses for C/C++ for array types
c*_build_qualified_type.
There has been already a related langhook
lang_hooks.types.copy_lang_qualifiers used solely for C++, so instead
of adding another langhook this adds a combined langhook for those two,
where C can handle array types specially and otherwise build_qualified_type,
while C++ ditto + do the function/method type modifiers propagation as
well.
Unfortunately there is a terrible array_as_string hack used by some
of the middle-end warnings which creates some array type with sometimes
an artificial attribute and then has hacks in the c-family type printing
to tweak the printed form, and this hack relies on the previous behavior
of build_type_attribute_qual_variant where it even for C/C++ kept
element type quals unmodified and added normally invalid quals on the
array type itself. The patch stops using build_type_attribute_qual_variant
for that and instead uses copy_node on the type and adjusts the quals and
adds the attribute to the copy and then ggc_frees it. Also it renames the
attribute from "array" to "array " to make it clear it is internal
attribute users can't specify even in vendor attributes.
2026-01-28 Jakub Jelinek <jakub@redhat.com>
PR c/101312
gcc/
* langhooks.h (struct lang_hooks_for_types): Remove
copy_lang_qualifiers. Add build_lang_qualified_type.
* langhooks.cc (lhd_build_lang_qualified_type): New function.
* langhooks-def.h (lhd_build_lang_qualified_type): Declare.
(LANG_HOOKS_COPY_LANG_QUALIFIERS): Remove.
(LANG_HOOKS_BUILD_LANG_QUALIFIED_TYPE): Add.
(LANG_HOOKS_FOR_TYPES_INITIALIZER): Use
LANG_HOOKS_BUILD_LANG_QUALIFIED_TYPE instead of
LANG_HOOKS_COPY_LANG_QUALIFIERS.
* attribs.cc (build_type_attribute_qual_variant): Use
lang_hooks.types.build_lang_qualified_type instead of
build_qualified_type and/or build_qualified_type with
optional lang_hooks.types.copy_lang_qualifiers call.
(attr_access::array_as_string): Use "array " attribute instead of
"array". If attribute has been created or intended quals differ
from quals of build_array_type, use copy_node and adjust quals and
attributes on the copy, print and then ggc_free.
gcc/c-family/
* c-pretty-print.cc (c_pretty_printer::direct_abstract_declarator):
Look up "array " attribute instead of "array".
gcc/c/
* c-tree.h (c_build_lang_qualified_type): Declare.
* c-objc-common.h (LANG_HOOKS_BUILD_LANG_QUALIFIED_TYPE): Define.
* c-objc-common.cc (c_build_lang_qualified_type): New function.
gcc/cp/
* cp-tree.h (cxx_build_lang_qualified_type): Declare.
* cp-objcp-common.h (LANG_HOOKS_COPY_LANG_QUALIFIERS): Remove.
(LANG_HOOKS_BUILD_LANG_QUALIFIED_TYPE): Define.
* tree.cc (cxx_build_lang_qualified_type): New function.
gcc/testsuite/
* c-c++-common/pr101312-1.c: New test.
* c-c++-common/pr101312-2.c: New test.
Diff:
---
gcc/attribs.cc | 55 +++++++++++++++++++++++++--------
gcc/c-family/c-pretty-print.cc | 2 +-
gcc/c/c-objc-common.cc | 11 +++++++
gcc/c/c-objc-common.h | 2 ++
gcc/c/c-tree.h | 1 +
gcc/cp/cp-objcp-common.h | 4 +--
gcc/cp/cp-tree.h | 1 +
gcc/cp/tree.cc | 21 +++++++++++++
gcc/langhooks-def.h | 5 +--
gcc/langhooks.cc | 10 ++++++
gcc/langhooks.h | 7 +++--
gcc/testsuite/c-c++-common/pr101312-1.c | 4 +++
gcc/testsuite/c-c++-common/pr101312-2.c | 5 +++
13 files changed, 107 insertions(+), 21 deletions(-)
diff --git a/gcc/attribs.cc b/gcc/attribs.cc
index db9a5c125ac8..942273757010 100644
--- a/gcc/attribs.cc
+++ b/gcc/attribs.cc
@@ -1322,14 +1322,15 @@ build_type_attribute_qual_variant (tree otype, tree attribute, int quals)
warning (OPT_Wattributes,
"ignoring attributes applied to %qT after definition",
TYPE_MAIN_VARIANT (ttype));
- return build_qualified_type (ttype, quals);
+ return lang_hooks.types.build_lang_qualified_type (ttype, NULL_TREE,
+ quals);
}
- ttype = build_qualified_type (ttype, TYPE_UNQUALIFIED);
- if (lang_hooks.types.copy_lang_qualifiers
- && otype != TYPE_MAIN_VARIANT (otype))
- ttype = (lang_hooks.types.copy_lang_qualifiers
- (ttype, TYPE_MAIN_VARIANT (otype)));
+ tree mtype = NULL_TREE;
+ if (otype != TYPE_MAIN_VARIANT (otype))
+ mtype = TYPE_MAIN_VARIANT (otype);
+ ttype = lang_hooks.types.build_lang_qualified_type (ttype, mtype,
+ TYPE_UNQUALIFIED);
tree dtype = ntype = build_distinct_type_copy (ttype);
@@ -1354,13 +1355,15 @@ build_type_attribute_qual_variant (tree otype, tree attribute, int quals)
else if (TYPE_CANONICAL (ntype) == ntype)
TYPE_CANONICAL (ntype) = TYPE_CANONICAL (ttype);
- ttype = build_qualified_type (ntype, quals);
- if (lang_hooks.types.copy_lang_qualifiers
- && otype != TYPE_MAIN_VARIANT (otype))
- ttype = lang_hooks.types.copy_lang_qualifiers (ttype, otype);
+ if (otype != TYPE_MAIN_VARIANT (otype))
+ mtype = otype;
+ else
+ mtype = NULL_TREE;
+ ttype = lang_hooks.types.build_lang_qualified_type (ntype, mtype, quals);
}
else if (TYPE_QUALS (ttype) != quals)
- ttype = build_qualified_type (ttype, quals);
+ ttype = lang_hooks.types.build_lang_qualified_type (ttype, NULL_TREE,
+ quals);
return ttype;
}
@@ -2652,6 +2655,7 @@ std::string
attr_access::array_as_string (tree type) const
{
std::string typstr;
+ bool free_type = false;
if (type == error_mark_node)
return std::string ();
@@ -2692,12 +2696,35 @@ attr_access::array_as_string (tree type) const
[*] is represented the same as [0] this hack only works for
the most significant bound like static and the others are
rendered as [0]. */
- arat = build_tree_list (get_identifier ("array"), flag);
+ arat = build_tree_list (get_identifier ("array "), flag);
}
const int quals = TYPE_QUALS (type);
type = build_array_type (eltype, index_type);
- type = build_type_attribute_qual_variant (type, arat, quals);
+ if (arat || TYPE_QUALS (type) != quals)
+ {
+ /* We create a new array type which is only used during
+ printing. Can't use build_type_attribute_qual_variant
+ because it might with some lang hooks e.g. try to push
+ qualifiers to the element type, while for the printing
+ this wants the element type qualifiers to be unmodified
+ and ARRAY_TYPE qualifiers to be a copy of the pointer
+ type qualifiers. Furthermore, a type with somtimes
+ weird qualifiers or artificial attribute should be
+ freed right after the use. */
+ type = copy_node (type);
+ if (arat)
+ {
+ TREE_CHAIN (arat) = TYPE_ATTRIBUTES (type);
+ TYPE_ATTRIBUTES (type) = arat;
+ }
+ TYPE_READONLY (type) = (quals & TYPE_QUAL_CONST) != 0;
+ TYPE_VOLATILE (type) = (quals & TYPE_QUAL_VOLATILE) != 0;
+ TYPE_ATOMIC (type) = (quals & TYPE_QUAL_ATOMIC) != 0;
+ TYPE_RESTRICT (type) = (quals & TYPE_QUAL_RESTRICT) != 0;
+ TYPE_ADDR_SPACE (type) = DECODE_QUAL_ADDR_SPACE (quals);
+ free_type = true;
+ }
}
/* Format the type using the current pretty printer. The generic tree
@@ -2705,6 +2732,8 @@ attr_access::array_as_string (tree type) const
std::unique_ptr<pretty_printer> pp (global_dc->clone_printer ());
pp_printf (pp.get (), "%qT", type);
typstr = pp_formatted_text (pp.get ());
+ if (free_type)
+ ggc_free (type);
return typstr;
}
diff --git a/gcc/c-family/c-pretty-print.cc b/gcc/c-family/c-pretty-print.cc
index d3d6c8bf8758..b084163e6a35 100644
--- a/gcc/c-family/c-pretty-print.cc
+++ b/gcc/c-family/c-pretty-print.cc
@@ -634,7 +634,7 @@ c_pretty_printer::direct_abstract_declarator (tree t)
add_space = true;
}
- if (tree arr = lookup_attribute ("array", TYPE_ATTRIBUTES (t)))
+ if (tree arr = lookup_attribute ("array ", TYPE_ATTRIBUTES (t)))
{
if (TREE_VALUE (arr))
{
diff --git a/gcc/c/c-objc-common.cc b/gcc/c/c-objc-common.cc
index 38e88733b509..49782d4eec8e 100644
--- a/gcc/c/c-objc-common.cc
+++ b/gcc/c/c-objc-common.cc
@@ -70,6 +70,17 @@ c_register_features ()
}
}
+/* Langhook for building qualified types. */
+
+tree
+c_build_lang_qualified_type (tree type, tree, int type_quals)
+{
+ if (TREE_CODE (type) == ARRAY_TYPE)
+ return c_build_qualified_type (type, type_quals);
+ else
+ return build_qualified_type (type, type_quals);
+}
+
bool
c_missing_noreturn_ok_p (tree decl)
{
diff --git a/gcc/c/c-objc-common.h b/gcc/c/c-objc-common.h
index e103646b67e8..8a67f6d99aa7 100644
--- a/gcc/c/c-objc-common.h
+++ b/gcc/c/c-objc-common.h
@@ -59,6 +59,8 @@ extern void c_register_features ();
#define LANG_HOOKS_PRINT_IDENTIFIER c_print_identifier
#undef LANG_HOOKS_TYPES_COMPATIBLE_P
#define LANG_HOOKS_TYPES_COMPATIBLE_P c_types_compatible_p
+#undef LANG_HOOKS_BUILD_LANG_QUALIFIED_TYPE
+#define LANG_HOOKS_BUILD_LANG_QUALIFIED_TYPE c_build_lang_qualified_type
#undef LANG_HOOKS_MISSING_NORETURN_OK_P
#define LANG_HOOKS_MISSING_NORETURN_OK_P c_missing_noreturn_ok_p
#undef LANG_HOOKS_BLOCK_MAY_FALLTHRU
diff --git a/gcc/c/c-tree.h b/gcc/c/c-tree.h
index 167f50e900c7..a63d1b674d64 100644
--- a/gcc/c/c-tree.h
+++ b/gcc/c/c-tree.h
@@ -780,6 +780,7 @@ extern tree c_finish_bc_name (location_t, tree, bool);
/* in c-objc-common.cc */
extern bool c_objc_common_init (void);
+extern tree c_build_lang_qualified_type (tree, tree, int);
extern bool c_missing_noreturn_ok_p (tree);
extern bool c_warn_unused_global_decl (const_tree);
extern void c_initialize_diagnostics (diagnostics::context *);
diff --git a/gcc/cp/cp-objcp-common.h b/gcc/cp/cp-objcp-common.h
index 2999b36a5ddc..441a250e8d3f 100644
--- a/gcc/cp/cp-objcp-common.h
+++ b/gcc/cp/cp-objcp-common.h
@@ -112,8 +112,8 @@ extern tree cxx_simulate_record_decl (location_t, const char *,
cxx_simulate_builtin_function_decl
#undef LANG_HOOKS_TYPE_HASH_EQ
#define LANG_HOOKS_TYPE_HASH_EQ cxx_type_hash_eq
-#undef LANG_HOOKS_COPY_LANG_QUALIFIERS
-#define LANG_HOOKS_COPY_LANG_QUALIFIERS cxx_copy_lang_qualifiers
+#undef LANG_HOOKS_BUILD_LANG_QUALIFIED_TYPE
+#define LANG_HOOKS_BUILD_LANG_QUALIFIED_TYPE cxx_build_lang_qualified_type
#undef LANG_HOOKS_MISSING_NORETURN_OK_P
#define LANG_HOOKS_MISSING_NORETURN_OK_P cp_missing_noreturn_ok_p
#undef LANG_HOOKS_BLOCK_MAY_FALLTHRU
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index c98c8e3eb746..19a426bfc2c0 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -7540,6 +7540,7 @@ extern tmpl_spec_kind current_tmpl_spec_kind (int);
extern tree cxx_builtin_function (tree decl);
extern tree cxx_builtin_function_ext_scope (tree decl);
extern tree cxx_simulate_builtin_function_decl (tree);
+extern tree cxx_build_lang_qualified_type (tree, tree, int);
extern tree check_elaborated_type_specifier (enum tag_types, tree, bool);
extern void warn_extern_redeclared_static (tree, tree);
extern tree cxx_comdat_group (tree);
diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc
index 55afa3efb273..2f386e16b9cc 100644
--- a/gcc/cp/tree.cc
+++ b/gcc/cp/tree.cc
@@ -1470,6 +1470,27 @@ c_build_qualified_type (tree type, int type_quals, tree /* orig_qual_type */,
return cp_build_qualified_type (type, type_quals);
}
+/* Implementation of the build_lang_qualified_type langhook. */
+tree
+cxx_build_lang_qualified_type (tree type, tree otype, int type_quals)
+{
+ /* Only handle ARRAY_TYPEs using cp_build_qualified_type, so that
+ quals are pushed to the element type. That is needed for PR101312.
+ For other types just keep using build_qualified_type with
+ cxx_copy_lang_qualifiers if needed, otherwise we can run into
+ issues with FUNCTION_TYPEs with cv-qualifier-seq vs. type-specifier,
+ or REFERENCE_TYPE which will error on certain TYPE_QUALS. */
+ if (TREE_CODE (type) == ARRAY_TYPE)
+ return cp_build_qualified_type (type, type_quals);
+ else
+ {
+ tree ret = build_qualified_type (type, type_quals);
+ if (otype)
+ ret = cxx_copy_lang_qualifiers (ret, otype);
+ return ret;
+ }
+}
+
/* Make a variant of TYPE, qualified with the TYPE_QUALS. Handles
arrays correctly. In particular, if TYPE is an array of T's, and
diff --git a/gcc/langhooks-def.h b/gcc/langhooks-def.h
index fc409ec08b96..1603bd8e63e0 100644
--- a/gcc/langhooks-def.h
+++ b/gcc/langhooks-def.h
@@ -63,6 +63,7 @@ extern tree lhd_type_for_size (unsigned precision, int unsignedp);
extern void lhd_incomplete_type_error (location_t, const_tree, const_tree);
extern tree lhd_type_promotes_to (tree);
extern void lhd_register_builtin_type (tree, const char *);
+extern tree lhd_build_lang_qualified_type (tree, tree, int);
extern bool lhd_decl_ok_for_sibcall (const_tree);
extern size_t lhd_tree_size (enum tree_code);
extern HOST_WIDE_INT lhd_to_target_charset (HOST_WIDE_INT);
@@ -212,7 +213,7 @@ extern tree lhd_unit_size_without_reusable_padding (tree);
#define LANG_HOOKS_OMP_FIRSTPRIVATIZE_TYPE_SIZES \
lhd_omp_firstprivatize_type_sizes
#define LANG_HOOKS_TYPE_HASH_EQ NULL
-#define LANG_HOOKS_COPY_LANG_QUALIFIERS NULL
+#define LANG_HOOKS_BUILD_LANG_QUALIFIED_TYPE lhd_build_lang_qualified_type
#define LANG_HOOKS_GET_ARRAY_DESCR_INFO NULL
#define LANG_HOOKS_GET_SUBRANGE_BOUNDS NULL
#define LANG_HOOKS_GET_TYPE_BIAS NULL
@@ -240,7 +241,7 @@ extern tree lhd_unit_size_without_reusable_padding (tree);
LANG_HOOKS_TYPE_MAX_SIZE, \
LANG_HOOKS_OMP_FIRSTPRIVATIZE_TYPE_SIZES, \
LANG_HOOKS_TYPE_HASH_EQ, \
- LANG_HOOKS_COPY_LANG_QUALIFIERS, \
+ LANG_HOOKS_BUILD_LANG_QUALIFIED_TYPE, \
LANG_HOOKS_GET_ARRAY_DESCR_INFO, \
LANG_HOOKS_GET_SUBRANGE_BOUNDS, \
LANG_HOOKS_GET_TYPE_BIAS, \
diff --git a/gcc/langhooks.cc b/gcc/langhooks.cc
index e2c7735596e0..d17d60737ea7 100644
--- a/gcc/langhooks.cc
+++ b/gcc/langhooks.cc
@@ -202,6 +202,16 @@ lhd_register_builtin_type (tree ARG_UNUSED (type),
{
}
+/* Return a version of the TYPE, qualified as indicated by the
+ TYPE_QUALS, if one exists. If no qualified version exists yet,
+ creates it and returns it. */
+tree
+lhd_build_lang_qualified_type (tree type, tree ARG_UNUSED (otype),
+ int type_quals)
+{
+ return build_qualified_type (type, type_quals);
+}
+
/* Invalid use of an incomplete type. */
void
lhd_incomplete_type_error (location_t ARG_UNUSED (loc),
diff --git a/gcc/langhooks.h b/gcc/langhooks.h
index 6eb5c1602f83..47996ff19137 100644
--- a/gcc/langhooks.h
+++ b/gcc/langhooks.h
@@ -134,9 +134,10 @@ struct lang_hooks_for_types
FUNCTION_TYPE or METHOD_TYPE. */
bool (*type_hash_eq) (const_tree, const_tree);
- /* If non-NULL, return TYPE1 with any language-specific modifiers copied from
- TYPE2. */
- tree (*copy_lang_qualifiers) (const_tree, const_tree);
+ /* Return a version of the TYPE, qualified as indicated by the
+ TYPE_QUALS in a language-specific way, if one exists, otherwise create it.
+ If OTYPE is non-NULL, copy extra language modifiers from it too. */
+ tree (*build_lang_qualified_type) (tree, tree, int);
/* Return TRUE if TYPE uses a hidden descriptor and fills in information
for the debugger about the array bounds, strides, etc. */
diff --git a/gcc/testsuite/c-c++-common/pr101312-1.c b/gcc/testsuite/c-c++-common/pr101312-1.c
new file mode 100644
index 000000000000..8d312db140ae
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr101312-1.c
@@ -0,0 +1,4 @@
+/* PR c/101312 */
+/* { dg-do compile } */
+
+volatile int a[1] __attribute__((may_alias));
diff --git a/gcc/testsuite/c-c++-common/pr101312-2.c b/gcc/testsuite/c-c++-common/pr101312-2.c
new file mode 100644
index 000000000000..16d77941eafe
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr101312-2.c
@@ -0,0 +1,5 @@
+/* PR c/101312 */
+/* { dg-do compile } */
+/* { dg-options "-g" } */
+
+volatile int a[1] __attribute__((may_alias));
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