On Wed, Sep 18, 2024 at 06:00:48PM +0200, Jakub Jelinek wrote:
> Hi!
>
> The _cpp_trigraph_map initialization used to be done for C99+ using
> designated initializers, but can't be done that way for C++ because
> the designated initializer support in C++ as array designators are just
> an extension there and don't allow skipping anything nor going backwards.
>
> But, we can get the same effect using C++14 constexpr constructor.
> With the following patch we get rid of the runtime initialization
> and the array can be in .rodata.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2024-09-18 Jakub Jelinek <ja...@redhat.com>
>
> * internal.h (_cpp_trigraph_map_s): New type for C++14 or later.
> (_cpp_trigraph_map_d): New variable for C++14 or later.
> (_cpp_trigraph_map): Define to _cpp_trigraph_map_d.map for C++14 or
> later.
> * init.cc (init_trigraph_map): Define to nothing for C++14 or later.
> (TRIGRAPH_MAP, END, s): Define differently for C++14 or later.
>
> --- libcpp/internal.h.jj 2024-09-12 18:16:49.993409101 +0200
> +++ libcpp/internal.h 2024-09-18 09:45:36.832570227 +0200
> @@ -666,6 +666,12 @@ struct cpp_embed_params
> compiler that supports C99. */
> #if HAVE_DESIGNATED_INITIALIZERS
> extern const unsigned char _cpp_trigraph_map[UCHAR_MAX + 1];
> +#elif __cpp_constexpr >= 201304L
> +extern const struct _cpp_trigraph_map_s {
> + unsigned char map[UCHAR_MAX + 1];
> + constexpr _cpp_trigraph_map_s ();
> +} _cpp_trigraph_map_d;
> +#define _cpp_trigraph_map _cpp_trigraph_map_d.map
> #else
> extern unsigned char _cpp_trigraph_map[UCHAR_MAX + 1];
> #endif
> --- libcpp/init.cc.jj 2024-09-13 16:09:32.701455021 +0200
> +++ libcpp/init.cc 2024-09-18 09:49:43.671189585 +0200
> @@ -41,8 +41,8 @@ static void read_original_directory (cpp
> static void post_options (cpp_reader *);
>
> /* If we have designated initializers (GCC >2.7) these tables can be
> - initialized, constant data. Otherwise, they have to be filled in at
> - runtime. */
> + initialized, constant data. Similarly for C++14 and later.
> + Otherwise, they have to be filled in at runtime. */
> #if HAVE_DESIGNATED_INITIALIZERS
>
> #define init_trigraph_map() /* Nothing. */
> @@ -52,6 +52,15 @@ __extension__ const uchar _cpp_trigraph_
> #define END };
> #define s(p, v) [p] = v,
>
> +#elif __cpp_constexpr >= 201304L
> +
> +#define init_trigraph_map() /* Nothing. */
> +#define TRIGRAPH_MAP \
> +constexpr _cpp_trigraph_map_s::_cpp_trigraph_map_s () : map {} {
> +#define END } \
> +constexpr _cpp_trigraph_map_s _cpp_trigraph_map_d;
> +#define s(p, v) map[p] = v;
> +
So with this we generate:
constexpr _cpp_trigraph_map_s::_cpp_trigraph_map_s () : map {} {
map['='] = '#'; map[')'] = ']'; map['!'] = '|';
map['('] = '['; map['\''] = '^'; map['>'] = '}';
map['/'] = '\\'; map['<'] = '{'; map['-'] = '~';
} constexpr _cpp_trigraph_map_s _cpp_trigraph_map_d;
That makes sense to me. The patch is OK.
Marek
