https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97468
Bug ID: 97468
Summary: gcc crashes when using __may_alias__ attribute
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: tangyixuan at mail dot dlut.edu.cn
Target Milestone: ---
Hi, the following code uses '__attribute__ ((__may_alias__))' to alias a struct
'S' to 'a'. However, gcc crashes at compilation time while clang successfully
compiles.
gcc doc:
https://gcc.gnu.org/onlinedocs/gcc-10.2.0/gcc/Common-Type-Attributes.html#Common-Type-Attributes
'Accesses through pointers to types with this attribute are not subject to
type-based alias analysis, but are instead assumed to be able to alias any
other type of objects.'
$ cat s.cpp
template<typename T> struct S{};
auto __attribute__ ((__may_alias__)) a=S<int>{};
$ g++ -c s.cpp
s.cpp:2:38: internal compiler error: in layout_type, at stor-layout.c:2618
2 | auto __attribute__ ((__may_alias__)) a=S<int>{};
| ^
0x62d384 layout_type(tree_node*)
../../gcc-11-20201011/gcc/stor-layout.c:2618
0xebaf34 type_hash_canon(unsigned int, tree_node*)
../../gcc-11-20201011/gcc/tree.c:7140
0x7e6beb build_type_attribute_qual_variant(tree_node*, tree_node*, int)
../../gcc-11-20201011/gcc/attribs.c:1166
0x7e8702 build_type_attribute_variant(tree_node*, tree_node*)
../../gcc-11-20201011/gcc/attribs.c:1377
0x7e8702 decl_attributes(tree_node**, tree_node*, int, tree_node*)
../../gcc-11-20201011/gcc/attribs.c:794
0x6d9e93 cplus_decl_attributes(tree_node**, tree_node*, int)
../../gcc-11-20201011/gcc/cp/decl2.c:1595
0x6cd1bf start_decl(cp_declarator const*, cp_decl_specifier_seq*, int,
tree_node*, tree_node*, tree_node**)
../../gcc-11-20201011/gcc/cp/decl.c:5267
0x7590ce cp_parser_init_declarator
../../gcc-11-20201011/gcc/cp/parser.c:20936
0x73a65c cp_parser_simple_declaration
../../gcc-11-20201011/gcc/cp/parser.c:13878
0x7630a6 cp_parser_declaration
../../gcc-11-20201011/gcc/cp/parser.c:13577
0x7636dd cp_parser_translation_unit
../../gcc-11-20201011/gcc/cp/parser.c:4793
0x7636dd c_parse_file()
../../gcc-11-20201011/gcc/cp/parser.c:44172
0x82f13d c_common_parse_file()
../../gcc-11-20201011/gcc/c-family/c-opts.c:1188
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
