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This marks structures which include a byte array as typeless storage for all C language modes. Bootstrapped and regression tested on x86_64. c: Add support for byte arrays in C2Y To get correct aliasing behavior requires that structures and unions that contain a byte array, i.e. an array of non-atomic character type (N3254), are marked with TYPE_TYPELESS_STORAGE. This change affects also earlier language modes. gcc/c/ * c-decl.cc (grokdeclarator, finish_struct): Set and propagate TYPE_TYPELESS_STORAGE. gcc/testsuite/ * gcc.dg/c2y-byte-alias-1.c: New test. * gcc.dg/c2y-byte-alias-2.c: New test. * gcc.dg/c2y-byte-alias-3.c: New test. diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc index 97f1d346835..7b8f622296f 100644 - --- a/gcc/c/c-decl.cc +++ b/gcc/c/c-decl.cc @@ -7502,12 +7502,18 @@ grokdeclarator (const struct c_declarator *declarator, modify the shared type, so we gcc_assert (itype) below. */ { + /* Identify typeless storage as introduced in C2Y + and supported also in earler language modes. */ + bool typeless = (char_type_p (type) + && !(type_quals & TYPE_QUAL_ATOMIC)) + || (AGGREGATE_TYPE_P (type) + && TYPE_TYPELESS_STORAGE (type)); + addr_space_t as = DECODE_QUAL_ADDR_SPACE (type_quals); if (!ADDR_SPACE_GENERIC_P (as) && as != TYPE_ADDR_SPACE (type)) type = build_qualified_type (type, ENCODE_QUAL_ADDR_SPACE (as)); - - - - type = build_array_type (type, itype); + type = build_array_type (type, itype, typeless); } if (type != error_mark_node) @@ -9659,6 +9665,10 @@ finish_struct (location_t loc, tree t, tree fieldlist, tree attributes, if (DECL_NAME (x) || RECORD_OR_UNION_TYPE_P (TREE_TYPE (x))) saw_named_field = true; + + if (AGGREGATE_TYPE_P (TREE_TYPE (x)) + && TYPE_TYPELESS_STORAGE (TREE_TYPE (x))) + TYPE_TYPELESS_STORAGE (t) = true; } detect_field_duplicates (fieldlist); @@ -9859,6 +9869,7 @@ finish_struct (location_t loc, tree t, tree fieldlist, tree attributes, TYPE_FIELDS (x) = TYPE_FIELDS (t); TYPE_LANG_SPECIFIC (x) = TYPE_LANG_SPECIFIC (t); TYPE_TRANSPARENT_AGGR (x) = TYPE_TRANSPARENT_AGGR (t); + TYPE_TYPELESS_STORAGE (x) = TYPE_TYPELESS_STORAGE (t); C_TYPE_FIELDS_READONLY (x) = C_TYPE_FIELDS_READONLY (t); C_TYPE_FIELDS_VOLATILE (x) = C_TYPE_FIELDS_VOLATILE (t); C_TYPE_FIELDS_NON_CONSTEXPR (x) = C_TYPE_FIELDS_NON_CONSTEXPR (t); diff --git a/gcc/testsuite/gcc.dg/c2y-byte-alias-1.c b/gcc/testsuite/gcc.dg/c2y-byte-alias-1.c new file mode 100644 index 00000000000..30bc2c09c2f - --- /dev/null +++ b/gcc/testsuite/gcc.dg/c2y-byte-alias-1.c @@ -0,0 +1,46 @@ +/* { dg-do run } */ +/* { dg-options "-std=c2y -O2" } */ + +struct f { _Alignas(int) char buf[sizeof(int)]; }; +struct f2 { struct f x; }; +union g { _Alignas(int) char buf[sizeof(int)]; }; + +[[gnu::noinline]] +int foo(struct f *p, int *q) +{ + *q = 1; + *p = (struct f){ }; + return *q; +} + +[[gnu::noinline]] +int foo2(struct f2 *p, int *q) +{ + *q = 1; + *p = (struct f2){ }; + return *q; +} + +[[gnu::noinline]] +int bar(union g *p, int *q) +{ + *q = 1; + *p = (union g){ }; + return *q; +} + + +int main() +{ + struct f p; + if (0 != foo(&p, (void*)&p.buf)) + __builtin_abort(); + + struct f2 p2; + if (0 != foo2(&p2, (void*)&p2.x.buf)) + __builtin_abort(); + + union g q; + if (0 != bar(&q, (void*)&q.buf)) + __builtin_abort(); +} diff --git a/gcc/testsuite/gcc.dg/c2y-byte-alias-2.c b/gcc/testsuite/gcc.dg/c2y-byte-alias-2.c new file mode 100644 index 00000000000..9bd2d18b386 - --- /dev/null +++ b/gcc/testsuite/gcc.dg/c2y-byte-alias-2.c @@ -0,0 +1,43 @@ +/* { dg-do run } */ +/* { dg-options "-std=c2y -O2" } */ + +struct f2 { + struct f { + _Alignas(int) char buf[sizeof(int)]; + } x[2]; + int i; +}; + +[[gnu::noinline]] +int foo2(struct f2 *p, int *q) +{ + *q = 1; + *p = (struct f2){ }; + return *q; +} + +struct g2 { + union g { + _Alignas(int) char buf[sizeof(int)]; + } x[2]; + int i; +}; + +[[gnu::noinline]] +int bar2(struct g2 *p, int *q) +{ + *q = 1; + *p = (struct g2){ }; + return *q; +} + +int main() +{ + struct f2 p2; + if (0 != foo2(&p2, (void*)&p2.x[0].buf)) + __builtin_abort(); + + struct g2 q2; + if (0 != bar2(&q2, (void*)&q2.x[0].buf)) + __builtin_abort(); +} diff --git a/gcc/testsuite/gcc.dg/c2y-byte-alias-3.c b/gcc/testsuite/gcc.dg/c2y-byte-alias-3.c new file mode 100644 index 00000000000..f88eab2e92f - --- /dev/null +++ b/gcc/testsuite/gcc.dg/c2y-byte-alias-3.c @@ -0,0 +1,47 @@ +/* { dg-do run } */ +/* { dg-options "-std=c2y -O2" } */ + +struct f { _Alignas(int) typeof(volatile char) buf[sizeof(int)]; }; +struct f2 { struct f x; }; +union g { _Alignas(int) volatile char buf[sizeof(int)]; }; + + +[[gnu::noinline]] +int foo(struct f *p, int *q) +{ + *q = 1; + *p = (struct f){ }; + return *q; +} + +[[gnu::noinline]] +int foo2(struct f2 *p, int *q) +{ + *q = 1; + *p = (struct f2){ }; + return *q; +} + +[[gnu::noinline]] +int bar(union g *p, int *q) +{ + *q = 1; + *p = (union g){ }; + return *q; +} + + +int main() +{ + struct f p; + if (0 != foo(&p, (void*)&p.buf)) + __builtin_abort(); + + struct f2 p2; + if (0 != foo2(&p2, (void*)&p2.x.buf)) + __builtin_abort(); + + union g q; + if (0 != bar(&q, (void*)&q.buf)) + __builtin_abort(); +} -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEEaj/uJqwNSIjsUpyzR1yvqQNbkRUFAmaSsBkACgkQR1yvqQNb kRWXDQ//Qy00jvmFjyjMYGBhowU5mNlweQbpK69VGUfGWqOlHk0XhJL/Ttk+pPey Z/E3z0wXdKtbqSyJa8akk2Ek/Z4Y9ic+/b1eSOMpPu3Lc7XYrCrfx1fYly6hOlW2 sOpiurmTxKaXySuWopk1uuhGwTlD2P4jV8qjjQSiK/T7kl2RD1gDCWRsLtZob8JJ 4ucbL0rTvuQoTrbUn+qMBpTCR5IR3AnBsoxCox7oFp/s2371sl5NaljTsOfamAzb Y0kRMr29G78HMi9sGRi0QKqU5I37mQF0MloQU1Fm6+8CYv2LNeFWG+OusLb1rUcH FKikGWV1muCBS+0OXajkyT6SkHTf3A/3MDc9V2KCxGf6OKdF9ktPpkToqZEgWJXi QzySfHEcZLyVpbe8CDUWeOdA721AAg9KO24rkjht2fuiyWOZSV2rKZZdSoHjVaxu 6foU9fpM6oEwZDSi02HoCXE85U04w58wo5qtsUQ0jghA0GRZZvprJNYjNUgBJPfb S4osZET1h5JQv0vpaHzVyZH48mSOw6OqmVVGRu1N2DYj9DFhhCKT34dQYdNELU6A WYKWWgeVyt6SGLdd0IRYThw7k0j5kSIO1I79SX9iMc3/6jfCchAJbQwejhuF2x2c UhfR15+CmTaoK/jgbDpI7fnBk5x2bBNq27ca8YqlrEQKWRRSXaU= =3NBa -----END PGP SIGNATURE-----