Add deprecation warning for literal PATWS under /x

This is explained in the perldelta changes in this commit.  We plan to
migrate to Unicode's definition of white-space to ignore under /x.  That
means we should raise a deprecation warning in the meantime if anyone
currently uses these characters in such a way as to have the meaning
changed when the migration is completed.

1 files changed, 9 insertions, 0 deletions

diff --git a/regcomp.c b/regcomp.c
index a8322ea1cf..2c7709aa88 100644
--- a/regcomp.c
+++ b/regcomp.c
@@ -10791,6 +10791,15 @@ tryagain:
 		    break;
 		default:    /* A literal character */
 
+                    if (! SIZE_ONLY
+                        && RExC_flags & RXf_PMf_EXTENDED
+                        && ckWARN(WARN_DEPRECATED)
+                        && is_PATWS_non_low(p, UTF))
+                    {
+                        vWARN_dep(p + ((UTF) ? UTF8SKIP(p) : 1),
+                                "Escape literal pattern white space under /x");
+                    }
+
 		  normal_default:
 		    if (UTF8_IS_START(*p) && UTF) {
 			STRLEN numlen;