use enumerated size for maxintwidth

Reference: /n/atom/patch/applied/fmtsrcsbits
Date: Tue Apr 15 20:35:49 CES 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/libc/fmt/dofmt.c	Tue Apr 15 20:34:59 2014
+++ /sys/src/libc/fmt/dofmt.c	Tue Apr 15 20:34:59 2014
@@ -305,11 +305,16 @@
 	return _fmtrcpy(f, x, 1);
 }
 
+enum {
+	/* %,#llb could emit a sign, "0b" and 64 digits with 21 commas */
+	Maxintwidth = 1 + 2 + 64 + 64/3,
+};
+
 /* fmt an integer */
 int
 _ifmt(Fmt *f)
 {
-	char buf[88], *p, *conv;
+	char buf[Maxintwidth + 1], *p, *conv;
 	uvlong vu;
 	ulong u;
 	uintptr pu;
--- /sys/src/libc/fmt/vsmprint.c	Tue Apr 15 20:34:59 2014
+++ /sys/src/libc/fmt/vsmprint.c	Tue Apr 15 20:34:59 2014
@@ -38,6 +38,7 @@
 	f->start = malloc(n);
 	if(f->start == nil)
 		return -1;
+	setmalloctag(f->start, getcallerpc(&f));
 	f->to = f->start;
 	f->stop = (char*)f->start + n - 1;
 	f->flush = fmtStrFlush;
@@ -60,11 +61,12 @@
 	f.args = args;
 	n = dofmt(&f, fmt);
 	if(f.start == nil)
-		return nil;
+		return nil;		/* realloc failed? */
 	if(n < 0){
 		free(f.start);
 		return nil;
 	}
+	setmalloctag(f.start, getcallerpc(&fmt));
 	*(char*)f.to = '\0';
 	return f.start;
 }