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Avoid printing NUL characters in 'message' (bug#75900)

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* src/xdisp.c (vmessage): Increase buffer size to fit an extra
multibyte character.  On buffer overflow, drop the last multibyte
character to determine an accurate byte length.
This commit is contained in:
Pip Cet 2025-01-27 13:06:27 -08:00 • committed by Paul Eggert
parent 0ed913cf46
commit 8812f526cf
1 changed files with 12 additions and 3 deletions
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15
src/xdisp.c
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@ -12587,10 +12587,19 @@ vmessage (const char *m, va_list ap)
ptrdiff_t len;
ptrdiff_t maxsize = FRAME_MESSAGE_BUF_SIZE (f);
USE_SAFE_ALLOCA;
char *message_buf = SAFE_ALLOCA (maxsize + 1);
len = doprnt (message_buf, maxsize, m, 0, ap);
char *message_buf = SAFE_ALLOCA (maxsize + MAX_MULTIBYTE_LENGTH);
len = doprnt (message_buf, maxsize + MAX_MULTIBYTE_LENGTH, m, 0, ap);
/* doprnt returns the buffer size minus one when it
truncated a multibyte sequence. Work around that by
truncating to the last valid multibyte head. */
if (len >= maxsize)
{
len = maxsize - 1;
while (!CHAR_HEAD_P (message_buf[len]))
len--;
message_buf[len] = 0;
}
message3 (make_string (message_buf, len));
SAFE_FREE ();
}