regcomp.h: change regexp_internal attribute from I32 to U32

This changes the name_list_idx attribute from I32 to a U32 as it will
never be negative, and as of a963d6d5acabdd8c7 a 0 can be safely used
to represent "no value" for items in the 'data' array.

I noticed this while cleaning up the offsets debug logic and updating
the perlreguts documentation, so I figured I might as well clean it up
at the same time.

1 files changed, 4 insertions, 1 deletions

diff --git a/regcomp.h b/regcomp.h
index 6b8dc27642..2705463474 100644
--- a/regcomp.h
+++ b/regcomp.h
@@ -71,7 +71,10 @@ typedef struct regexp_internal {
                                    strictly reserved for internal purposes. */
         struct reg_code_blocks *code_blocks;/* positions of literal (?{}) */
         U32 proglen;            /* size of the compiled program in regnodes */
-        int name_list_idx;        /* Optional data index of an array of paren names */
+        U32 name_list_idx;      /* Optional data index of an array of paren names,
+                                   only valid when RXp_PAREN_NAMES(prog) is true,
+                                   0 means "no value" like any other index into the
+                                   data array.*/
         regnode program[1];	/* Unwarranted chumminess with compiler. */
 } regexp_internal;