vmake_stringf: Copy the va_list argument for the second vsnprintf call.

It needs to be copied, otherwise the second call to vsnprintf will be passed
a va_list that has been messed up by the first call, and weird segfaults will
occur.  (They did for me.)

1 files changed, 4 insertions, 1 deletions

diff --git a/crawl-ref/source/libutil.cc b/crawl-ref/source/libutil.cc
index 26243f405c..bd3440d0fb 100644
--- a/crawl-ref/source/libutil.cc
+++ b/crawl-ref/source/libutil.cc
@@ -143,12 +143,15 @@ std::string strip_filename_unsafe_chars(const std::string &s)
 std::string vmake_stringf(const char* s, va_list args)
 {
     char buf1[400];
+    va_list orig_args;
+    va_copy(orig_args, args);
     size_t len = vsnprintf(buf1, sizeof buf1, s, args);
     if (len < sizeof buf1)
         return (buf1);
 
     char *buf2 = (char*)malloc(len + 1);
-    vsnprintf(buf2, len + 1, s, args);
+    vsnprintf(buf2, len + 1, s, orig_args);
+    va_end(orig_args);
     std::string ret(buf2);
     free(buf2);