Re: [PATCH] [vxworks] make wint_t and wchar_t the same distinct type

[Jason Merrill <jason@redhat.com>]

On 2/17/23 23:04, Alexandre Oliva wrote:
> 
> We used to define WINT_TYPE to WCHAR_TYPE, so that both wint_t and
> wchar_t mapped to the same underlying type, but this caused a glitch
> in Wstringop-overflow-6.C: on vxworks, wint_t is typedef'ed to
> wchar_t

And fixing that isn't an option?  Do the integer builtins work properly 
if we force them to use wchar_t instead of an integer type?

> headers got included in the test that declared functions that
> take wint_t parameters, and those conflicted with the builtin
> declarations that had wint_t mapped to the underlying integral type.
> 
> The problem is that, in C++, wchar_t is a distinct type.  Having
> wint_t be a typedef to wchar_t in the headers, but a typedef to
> wchar_t's underlying integral type in builtins, makes for mismatches
> between the declarations.
> 
> This patch defines WINT_TYPE to "wchar_t" for vxworks, and adjusts the
> fallout, namely:
> 
> - since wchar_t may not have been defined yet when
>    c_common_nodes_and_builtins runs, use the node already reserved for
>    wchar_t for wint_t when WINT_TYPE is defined to wchar_t.
> 
> - for the same reason, when WINT_TYPE is wchar_t and we're not
>    compiling C++ where wchar_t is a compiler built-in, define
>    __WINT_TYPE__ to WCHAR_TYPE rather than WINT_TYPE, because wchar_t
>    may not even be defined in the translation unit.
> 
> - recognize and handle wchar_type_node when type_suffix is called for
>    wint_type_node.
> 
> Regstrapped on x86_64-linux-gnu.
> Tested on arm-vxworks7 (gcc-12) and arm-eabi (trunk).  Ok to install?
> 
> for  gcc/ChangeLog
> 
> 	* config/vx-common.h (WINT_TYPE): Alias to "wchar_t".
> 
> for  gcc/c-family/ChangeLog
> 
> 	* c-common.cc (c_common_nodes_and_builtins): Take
> 	wchar_type_node for wint_type_node when aliased.
> 	(c_stddef_cpp_builtins): Define __WINT_TYPE__, when aliased to
> 	wchar_t, to the underlying type rather than wchar_t in
> 	non-C++.
> 	* c-cppbuiltin.cc (type_suffix): Handle wchar_type_node.
> ---
>   gcc/c-family/c-common.cc     |   16 +++++++++++++---
>   gcc/c-family/c-cppbuiltin.cc |    2 ++
>   gcc/config/vx-common.h       |    2 +-
>   3 files changed, 16 insertions(+), 4 deletions(-)
> 
> diff --git a/gcc/c-family/c-common.cc b/gcc/c-family/c-common.cc
> index ae92cd5adaf5e..a92597c2f544f 100644
> --- a/gcc/c-family/c-common.cc
> +++ b/gcc/c-family/c-common.cc
> @@ -4576,8 +4576,11 @@ c_common_nodes_and_builtins (void)
>     char32_array_type_node
>       = build_array_type (char32_type_node, array_domain_type);
>   
> -  wint_type_node =
> -    TREE_TYPE (identifier_global_value (get_identifier (WINT_TYPE)));
> +  if (strcmp (WINT_TYPE, "wchar_t") == 0)
> +    wint_type_node = wchar_type_node;
> +  else
> +    wint_type_node =
> +      TREE_TYPE (identifier_global_value (get_identifier (WINT_TYPE)));
>   
>     intmax_type_node =
>       TREE_TYPE (identifier_global_value (get_identifier (INTMAX_TYPE)));
> @@ -5359,7 +5362,14 @@ c_stddef_cpp_builtins(void)
>     builtin_define_with_value ("__SIZE_TYPE__", SIZE_TYPE, 0);
>     builtin_define_with_value ("__PTRDIFF_TYPE__", PTRDIFF_TYPE, 0);
>     builtin_define_with_value ("__WCHAR_TYPE__", MODIFIED_WCHAR_TYPE, 0);
> -  builtin_define_with_value ("__WINT_TYPE__", WINT_TYPE, 0);
> +  /* C++ has wchar_t as a builtin type, C doesn't, so if WINT_TYPE
> +     maps to wchar_t, define it to the underlying WCHAR_TYPE in C, and
> +     to wchar_t in C++, so the desired type equivalence holds.  */
> +  if (!c_dialect_cxx ()
> +      && strcmp (WINT_TYPE, "wchar_t") == 0)
> +    builtin_define_with_value ("__WINT_TYPE__", WCHAR_TYPE, 0);
> +  else
> +    builtin_define_with_value ("__WINT_TYPE__", WINT_TYPE, 0);
>     builtin_define_with_value ("__INTMAX_TYPE__", INTMAX_TYPE, 0);
>     builtin_define_with_value ("__UINTMAX_TYPE__", UINTMAX_TYPE, 0);
>     if (flag_char8_t)
> diff --git a/gcc/c-family/c-cppbuiltin.cc b/gcc/c-family/c-cppbuiltin.cc
> index b333f97fd3237..98f5aef2af95d 100644
> --- a/gcc/c-family/c-cppbuiltin.cc
> +++ b/gcc/c-family/c-cppbuiltin.cc
> @@ -1903,6 +1903,8 @@ type_suffix (tree type)
>   	      systems use it anyway.  */
>   	   || type == char_type_node)
>       is_long = 0;
> +  else if (type == wchar_type_node)
> +    return type_suffix (underlying_wchar_type_node);
>     else
>       gcc_unreachable ();
>   
> diff --git a/gcc/config/vx-common.h b/gcc/config/vx-common.h
> index 83580d0dec288..9733c90fe4c6f 100644
> --- a/gcc/config/vx-common.h
> +++ b/gcc/config/vx-common.h
> @@ -69,7 +69,7 @@ along with GCC; see the file COPYING3.  If not see
>   #undef WINT_TYPE_SIZE
>   #define WINT_TYPE_SIZE WCHAR_TYPE_SIZE
>   #undef WINT_TYPE
> -#define WINT_TYPE WCHAR_TYPE
> +#define WINT_TYPE "wchar_t"
>   
>   /* ---------------------- Debug and unwind info formats ------------------  */
>   
>