exec: Do not allocate stack string in padvance

Many callers of padvance immediately free the allocated string
so this patch moves the stalloc call to the caller.  Instead of
returning the allocated string, padvance now returns the length
to allocate (this may be longer than the actual string length,
even including the NUL).  For the case where we would previously
return NULL, we now return -1.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 5 insertions, 2 deletions

diff --git a/src/mail.c b/src/mail.c
index 02e07f7..7f9e49d 100644
--- a/src/mail.c
+++ b/src/mail.c
@@ -77,9 +77,12 @@ chkmail(void)
 	setstackmark(&smark);
 	mpath = mpathset() ? mpathval() : mailval();
 	for (mtp = mailtime; mtp < mailtime + MAXMBOXES; mtp++) {
-		p = padvance(&mpath, nullstr);
-		if (p == NULL)
+		int len;
+
+		len = padvance(&mpath, nullstr);
+		if (!len)
 			break;
+		p = stackblock();
 		if (*p == '\0')
 			continue;
 		for (q = p ; *q ; q++);