Switch rb_category_warn{,ing} to accept an rb_warning_category_t

Since we decided to only allowing specific warning categories,
there is no reason to have an API that accepts a general string,
as it is more error-prone.  Switch to only allowing the specific
warning categories.

As rb_category_warn{,ing} are public API, this requires making
rb_warning_category_t public API as well.

error.c

@@ -77,6 +77,7 @@ static ID id_deprecated;
 static ID id_experimental;
 static VALUE sym_category;
 static VALUE warning_categories;
+static VALUE warning_category_t_map;
 
 extern const char ruby_description[];
 
@@ -403,11 +404,11 @@ rb_warn(const char *fmt, ...)
 }
 
 void
-rb_category_warn(const char *category, const char *fmt, ...)
+rb_category_warn(rb_warning_category_t category, const char *fmt, ...)
 {
     if (!NIL_P(ruby_verbose)) {
         with_warning_string(mesg, 0, fmt) {
-            rb_warn_category(mesg, ID2SYM(rb_intern(category)));
+            rb_warn_category(mesg, rb_hash_fetch(warning_category_t_map, INT2NUM(category)));
         }
     }
 }
@@ -435,11 +436,11 @@ rb_warning(const char *fmt, ...)
 
 /* rb_category_warning() reports only in verbose mode */
 void
-rb_category_warning(const char *category, const char *fmt, ...)
+rb_category_warning(rb_warning_category_t category, const char *fmt, ...)
 {
     if (RTEST(ruby_verbose)) {
         with_warning_string(mesg, 0, fmt) {
-            rb_warn_category(mesg, ID2SYM(rb_intern(category)));
+            rb_warn_category(mesg, rb_hash_fetch(warning_category_t_map, INT2NUM(category)));
         }
     }
 }
@@ -2839,6 +2840,13 @@ Init_Exception(void)
     rb_gc_register_mark_object(warning_categories);
     rb_hash_aset(warning_categories, ID2SYM(rb_intern_const("deprecated")), Qtrue);
     rb_obj_freeze(warning_categories);
+
+    warning_category_t_map = rb_hash_new();
+    rb_gc_register_mark_object(warning_category_t_map);
+    rb_hash_aset(warning_category_t_map, INT2NUM(RB_WARN_CATEGORY_NONE), Qnil);
+    rb_hash_aset(warning_category_t_map, INT2NUM(RB_WARN_CATEGORY_DEPRECATED), ID2SYM(rb_intern_const("deprecated")));
+    rb_hash_aset(warning_category_t_map, INT2NUM(RB_WARN_CATEGORY_EXPERIMENTAL), ID2SYM(rb_intern_const("experimental")));
+    rb_obj_freeze(warning_category_t_map);
 }
 
 void

include/ruby/internal/error.h

@@ -29,6 +29,13 @@ RBIMPL_SYMBOL_EXPORT_BEGIN()
 VALUE rb_errinfo(void);
 void rb_set_errinfo(VALUE);
 
+typedef enum {
+    RB_WARN_CATEGORY_NONE,
+    RB_WARN_CATEGORY_DEPRECATED,
+    RB_WARN_CATEGORY_EXPERIMENTAL,
+    RB_WARN_CATEGORY_ALL_BITS = 0x6 /* no RB_WARN_CATEGORY_NONE bit */
+} rb_warning_category_t;
+
 /* for rb_readwrite_sys_fail first argument */
 enum rb_io_wait_readwrite {RB_IO_WAIT_READABLE, RB_IO_WAIT_WRITABLE};
 #define RB_IO_WAIT_READABLE RB_IO_WAIT_READABLE
@@ -63,12 +70,12 @@ VALUE *rb_ruby_debug_ptr(void);
 
 /* reports if `-W' specified */
 PRINTF_ARGS(void rb_warning(const char*, ...), 1, 2);
-PRINTF_ARGS(void rb_category_warning(const char*, const char*, ...), 2, 3);
+PRINTF_ARGS(void rb_category_warning(rb_warning_category_t category, const char*, ...), 2, 3);
 PRINTF_ARGS(void rb_compile_warning(const char *, int, const char*, ...), 3, 4);
 PRINTF_ARGS(void rb_sys_warning(const char*, ...), 1, 2);
 /* reports always */
 COLDFUNC PRINTF_ARGS(void rb_warn(const char*, ...), 1, 2);
-COLDFUNC PRINTF_ARGS(void rb_category_warn(const char *, const char*, ...), 2, 3);
+COLDFUNC PRINTF_ARGS(void rb_category_warn(rb_warning_category_t category, const char*, ...), 2, 3);
 PRINTF_ARGS(void rb_compile_warn(const char *, int, const char*, ...), 3, 4);
 
 RBIMPL_SYMBOL_EXPORT_END()

internal/error.h

@@ -40,13 +40,6 @@
 #endif
 
 /* error.c */
-typedef enum {
-    RB_WARN_CATEGORY_NONE,
-    RB_WARN_CATEGORY_DEPRECATED,
-    RB_WARN_CATEGORY_EXPERIMENTAL,
-    RB_WARN_CATEGORY_ALL_BITS = 0x6, /* no RB_WARN_CATEGORY_NONE bit */
-} rb_warning_category_t;
-
 extern long rb_backtrace_length_limit;
 extern VALUE rb_eEAGAIN;
 extern VALUE rb_eEWOULDBLOCK;