2 files changed, 18 insertions, 6 deletions
diff --git a/hw4/l4basic/l4str.c b/hw4/l4basic/l4str.c
index ad8c2e6..c1f6c51 100644
--- a/hw4/l4basic/l4str.c
+++ b/hw4/l4basic/l4str.c
@@ -25,18 +25,28 @@ bool lbs_str_has_suffix (const char* str, const char* suffix) {
 char* lbs_str_printf (const char* format, ...) {
     va_list ap;
     char* newstr;
-    int len;
 
     va_start (ap, format);
-    len = vsnprintf (NULL, 0, format, ap) + 1;
+    newstr = lbs_str_vprintf (format, ap);
     va_end (ap);
 
+    return newstr;
+}
+
+char* lbs_str_vprintf (const char* format, va_list ap) {
+    va_list ap1, ap2;
+    char* newstr;
+    int len;
+
+    va_copy (ap1, ap);
+    len = vsnprintf (NULL, 0, format, ap1) + 1;
+    va_end (ap1);
+
     newstr = xmalloc (len);
 
-    va_start (ap, format);
-    vsnprintf (newstr, len, format, ap);
-    va_end (ap);
+    va_copy (ap2, ap);
+    vsnprintf (newstr, len, format, ap2);
+    va_end (ap2);
 
     return newstr;
 }
-
diff --git a/hw4/l4basic/l4str.h b/hw4/l4basic/l4str.h
index cda3c1d..b041e22 100644
--- a/hw4/l4basic/l4str.h
+++ b/hw4/l4basic/l4str.h
@@ -3,11 +3,13 @@
 #define LBS_STR_H
 
 #include <l4common.h>
+#include <stdarg.h>
 
 #define LBS_STR_STATIC_STRLEN(x) (sizeof(x)/sizeof(char) - 1)
 #define LBS_STR_ARRAY_LEN(x,t)   (sizeof(x)/sizeof(t))
 
 bool    lbs_str_has_suffix       (const char* str, const char* suffix);
 char*   lbs_str_printf           (const char* format, ...);
+char*   lbs_str_vprintf          (const char* format, va_list ap);
 
 #endif /* LBS_STR_H */