Fix spurious regexp reentrancy error

* src/search.c (compile_pattern): Don't give up if the last regexp
cache entry is busy.  Instead, use the last (least recently used)
non-busy entry, and only signal a reentrancy error if there is no free
entry at all (Bug#34910).

1 files changed, 9 insertions, 6 deletions

diff --git a/src/search.c b/src/search.c
index e15e2b94e5f..07ff0e47643 100644
--- a/src/search.c
+++ b/src/search.c
@@ -198,11 +198,13 @@ static struct regexp_cache *
 compile_pattern (Lisp_Object pattern, struct re_registers *regp,
                  Lisp_Object translate, bool posix, bool multibyte)
 {
-  struct regexp_cache *cp, **cpp;
+  struct regexp_cache *cp, **cpp, **lru_nonbusy;
 
-  for (cpp = &searchbuf_head; ; cpp = &cp->next)
+  for (cpp = &searchbuf_head, lru_nonbusy = NULL; ; cpp = &cp->next)
     {
       cp = *cpp;
+      if (!cp->busy)
+        lru_nonbusy = cpp;
       /* Entries are initialized to nil, and may be set to nil by
          compile_pattern_1 if the pattern isn't valid.  Don't apply
          string accessors in those cases.  However, compile_pattern_1
@@ -222,13 +224,14 @@ compile_pattern (Lisp_Object pattern, struct re_registers *regp,
           && cp->buf.charset_unibyte == charset_unibyte)
         break;
 
-      /* If we're at the end of the cache, compile into the nil cell
-         we found, or the last (least recently used) cell with a
-         string value.  */
+      /* If we're at the end of the cache, compile into the last
+         (least recently used) non-busy cell in the cache.  */
       if (cp->next == 0)
         {
-          if (cp->busy)
+          if (!lru_nonbusy)
             error ("Too much matching reentrancy");
+          cpp = lru_nonbusy;
+          cp = *cpp;
         compile_it:
           eassert (!cp->busy);
           compile_pattern_1 (cp, pattern, translate, posix);