Fix memmove() invocation with src/dst being NULL

This fixes a segmentation fault on some systems.

1 files changed, 5 insertions, 2 deletions

diff --git a/st.c b/st.c
index b1d3791..bb8c365 100644
--- a/st.c
+++ b/st.c
@@ -2788,8 +2788,11 @@ tresize(int col, int row) {
                 free(term.line[i]);
                 free(term.alt[i]);
         }
-        memmove(term.line, term.line + i, row * sizeof(Line));
-        memmove(term.alt, term.alt + i, row * sizeof(Line));
+        /* ensure that both src and dst are not NULL */
+        if (i > 0) {
+                memmove(term.line, term.line + i, row * sizeof(Line));
+                memmove(term.alt, term.alt + i, row * sizeof(Line));
+        }
         for(i += row; i < term.row; i++) {
                 free(term.line[i]);
                 free(term.alt[i]);