[hackers] [dmenu] tab-complete: figure out the size before copying || NRK

[git]

commit 528d39b011afb7ef6fd794ba6b74155d4e69bc68
Author:     NRK <n...@disroot.org>
AuthorDate: Thu Sep 1 23:51:43 2022 +0600
Commit:     Hiltjo Posthuma <hil...@codemadness.org>
CommitDate: Fri Sep 2 13:00:48 2022 +0200

    tab-complete: figure out the size before copying
    
    we already need to know the string length since `cursor` needs to be
    adjusted.
    
    so just calculate the length beforehand and use `memcpy` to copy exactly
    as much as needed (as opposed to `strncpy` which always writes `n`
    bytes).

diff --git a/dmenu.c b/dmenu.c
index 969f6d8..6b285df 100644
--- a/dmenu.c
+++ b/dmenu.c
@@ -517,9 +517,9 @@ insert:
        case XK_Tab:
                if (!sel)
                        return;
-               strncpy(text, sel->text, sizeof text - 1);
+               cursor = strnlen(sel->text, sizeof text - 1);
+               memcpy(text, sel->text, cursor);
                text[sizeof text - 1] = '\0';
-               cursor = strlen(text);
                match();
                break;
        }