Introduce ga_append_via_ptr() and GA_APPEND_VIA_PTR()

Similar to GA_APPEND(). Replaces this pattern:

    ga_grow(&ga, 1);
    item_type *p = ((item_type *)ga.ga_data) + ga.ga_len;
    p->field1 = v1;
    p->field2 = v2;
    ga.ga_len++;

1 files changed, 3 insertions, 8 deletions

diff --git a/src/nvim/regexp.c b/src/nvim/regexp.c
index 29f090c6b7..0ead83e0d4 100644
--- a/src/nvim/regexp.c
+++ b/src/nvim/regexp.c
@@ -4177,7 +4177,6 @@ regmatch (
         case BACK:
         {
           int i;
-          backpos_T       *bp;
 
           /*
            * When we run into BACK we need to check if we don't keep
@@ -4187,17 +4186,13 @@ regmatch (
            * The positions are stored in "backpos" and found by the
            * current value of "scan", the position in the RE program.
            */
-          bp = (backpos_T *)backpos.ga_data;
+          backpos_T *bp = (backpos_T *)backpos.ga_data;
           for (i = 0; i < backpos.ga_len; ++i)
             if (bp[i].bp_scan == scan)
               break;
           if (i == backpos.ga_len) {
-            /* First time at this BACK, make room to store the pos. */
-            ga_grow(&backpos, 1);
-            /* get "ga_data" again, it may have changed */
-            bp = (backpos_T *)backpos.ga_data;
-            bp[i].bp_scan = scan;
-            ++backpos.ga_len;
+            backpos_T *p = GA_APPEND_VIA_PTR(backpos_T, &backpos);
+            p->bp_scan = scan;
           } else if (reg_save_equal(&bp[i].bp_pos))
             /* Still at same position as last time, fail. */
             status = RA_NOMATCH;