fix buffer overflow when handling long composed input

To reproduce the issue:

"
If you already have the multi-key enabled on your system, then add this line
to your ~/.XCompose file:

[...]
<question> <T> <E> <S> <T> <question> :
"1234567890123456789012345678901234567890123456789012345678901234567890"
"

Reported by and an initial patch by Andy Gozas <andy@gozas.me>, thanks!

Adapted the patch, for now st (like dmenu) handles a fixed amount of composed
characters, or otherwise ignores it. This is done for simplicity sake.

1 files changed, 6 insertions, 3 deletions

diff --git a/x.c b/x.c
index 2a3bd38..aa09997 100644
--- a/x.c
+++ b/x.c
@@ -1833,7 +1833,7 @@ void
 kpress(XEvent *ev)
 {
         XKeyEvent *e = &ev->xkey;
-        KeySym ksym;
+        KeySym ksym = NoSymbol;
         char buf[64], *customkey;
         int len;
         Rune c;
@@ -1843,10 +1843,13 @@ kpress(XEvent *ev)
         if (IS_SET(MODE_KBDLOCK))
                 return;
 
-        if (xw.ime.xic)
+        if (xw.ime.xic) {
                 len = XmbLookupString(xw.ime.xic, e, buf, sizeof buf, &ksym, &status);
-        else
+                if (status == XBufferOverflow)
+                        return;
+        } else {
                 len = XLookupString(e, buf, sizeof buf, &ksym, NULL);
+        }
         /* 1. shortcuts */
         for (bp = shortcuts; bp < shortcuts + LEN(shortcuts); bp++) {
                 if (ksym == bp->keysym && match(bp->mod, e->state)) {