use vsnprintf instead of snprintf in string_printf function

Also, revert to old location: Utils.hpp and utils.cpp

src/libslic3r/Utils.hpp

@@ -93,6 +93,8 @@ namespace PerlUtils {
     extern std::string path_to_parent_path(const char *src);
 };
 
+std::string string_printf(const char *format, ...);
+
 // Standard "generated by Slic3r version xxx timestamp xxx" header string, 
 // to be placed at the top of Slic3r generated files.
 std::string header_slic3r_generated();

src/libslic3r/libslic3r.h

@@ -230,23 +230,6 @@ static inline bool is_approx(Number value, Number test_value)
     return std::fabs(double(value) - double(test_value)) < double(EPSILON);
 }
 
-template<class...Args>
-std::string string_printf(const char *const _fmt, Args &&...args)
-{
-    static const size_t INITIAL_LEN = 1024;
-    std::vector<char> buffer(INITIAL_LEN, '\0');
-    
-    auto fmt = std::string("%s") + _fmt;
-    int bufflen = snprintf(buffer.data(), INITIAL_LEN - 1, fmt.c_str(), "", std::forward<Args>(args)...);
-    
-    if (bufflen >= int(INITIAL_LEN)) {
-        buffer.resize(size_t(bufflen) + 1);
-        snprintf(buffer.data(), buffer.size(), fmt.c_str(), "", std::forward<Args>(args)...);
-    }
-    
-    return std::string(buffer.begin(), buffer.begin() + bufflen);
-}
-
 } // namespace Slic3r
 
 #endif

src/libslic3r/utils.cpp

@@ -577,6 +577,27 @@ namespace PerlUtils {
     std::string path_to_parent_path(const char *src)    { return boost::filesystem::path(src).parent_path().string(); }
 };
 
+
+std::string string_printf(const char *format, ...)
+{
+    va_list args1;
+    va_start(args1, format);
+    va_list args2;
+    va_copy(args2, args1);
+    
+    static const size_t INITIAL_LEN = 1024;
+    std::vector<char> buffer(INITIAL_LEN, '\0');
+    
+    int bufflen = ::vsnprintf(buffer.data(), INITIAL_LEN - 1, format, args1);
+    
+    if (bufflen >= int(INITIAL_LEN)) {
+        buffer.resize(size_t(bufflen) + 1);
+        ::vsnprintf(buffer.data(), buffer.size(), format, args2);
+    }
+    
+    return std::string(buffer.begin(), buffer.begin() + bufflen);
+}
+
 std::string header_slic3r_generated()
 {
     return std::string("generated by " SLIC3R_APP_NAME " " SLIC3R_VERSION " on " ) + Utils::utc_timestamp();

tests/libslic3r/libslic3r_tests.cpp

@@ -1,6 +1,6 @@
 #include <catch_main.hpp>
 
-#include "libslic3r/libslic3r.h"
+#include "libslic3r/Utils.hpp"
 
 namespace {