 +}
 +
 +const char* convert(char *dst, size_t dstlen, const char *src) {
++    if (dst == NULL || dstlen == 0 || src == NULL) {
++        return dst;
++    }
++
 +    const char* srcit = src;
 +    const char* srcbeg = src;
 +    char* dstit = dst;

+    }
+
+    sub_convert(&srcbeg, &srcit, &dstit, dstend, &in_string);
+
+    return dst;
+}

+    int prev_was_space = 0;
+    int in_string = false;
+
+    for (; *srcit != '\0'; ++srcit) {
+        if (*srcit == '\'' || *srcit == '"') {
+            if (in_string == *srcit) {
+                in_string = 0;
