X-Git-Url: http://nsz.repo.hu/git/?p=musl;a=blobdiff_plain;f=src%2Fstdio%2Fvsnprintf.c;h=6f19b0287234bd6f9ff414f5dfd490a563a77bd3;hp=1f316ca48207f986a6dd0617269e85f3e977fc06;hb=f1b23d41cff432a8d0939af427fa005b4a4f95d7;hpb=9ae8d5fc71a4b61ec826d58f03f7b543755fb1d4

diff --git a/src/stdio/vsnprintf.c b/src/stdio/vsnprintf.c
index 1f316ca4..6f19b028 100644
--- a/src/stdio/vsnprintf.c
+++ b/src/stdio/vsnprintf.c
@@ -2,33 +2,37 @@
 
 static size_t sn_write(FILE *f, const unsigned char *s, size_t l)
 {
-	/* pretend to succeed, but discard data */
+	size_t k = f->wend - f->wpos;
+	if (k > l) k = l;
+	memcpy(f->wpos, s, k);
+	f->wpos += k;
+	/* pretend to succeed, but discard extra data */
 	return l;
 }
 
-int vsnprintf(char *s, size_t n, const char *fmt, va_list ap)
+int vsnprintf(char *restrict s, size_t n, const char *restrict fmt, va_list ap)
 {
 	int r;
-	FILE f;
-	unsigned char buf[1];
+	char b;
+	FILE f = { .lbf = EOF, .write = sn_write, .lock = -1 };
 
-	memset(&f, 0, sizeof(FILE));
-	f.lbf = EOF;
-	f.write = sn_write;
-	f.buf_size = 1;
-	f.buf = buf;
-	f.lock = -1;
-	if (n > INT_MAX) {
-		errno = EOVERFLOW;
-		return -1;
-	} else if (n > 0) {
-		if (n > (char *)0+SIZE_MAX-s) n = (char *)0+SIZE_MAX-s;
-		f.wpos = (void *)s;
-		f.wbase = f.wend = (void *)(s+n-1);
-		f.wstop = f.wend - 1;
+	if (n-1 > INT_MAX-1) {
+		if (n) {
+			errno = EOVERFLOW;
+			return -1;
+		}
+		s = &b;
+		n = 1;
 	}
+
+	/* Ensure pointers don't wrap if "infinite" n is passed in */
+	if (n > (char *)0+SIZE_MAX-s-1) n = (char *)0+SIZE_MAX-s-1;
+	f.buf_size = n;
+	f.buf = f.wpos = (void *)s;
+	f.wbase = f.wend = (void *)(s+n);
 	r = vfprintf(&f, fmt, ap);
-	/* wpos points just after last byte written, or to s+n-1 (wbase) */
-	*f.wpos = 0;
+
+	/* Null-terminate, overwriting last char if dest buffer is full */
+	if (n) f.wpos[-(f.wpos == f.wend)] = 0;
 	return r;
 }