Ok, I’ve investigated some more. The “-fpermissive” flag is only supported by g++, which we use for Android and Linux. For clang++, the flag won’t do anything. And the pragma directives are only supported by g++.
So, for it to work on iOS/OSX/HTML5, you currently still need to compile it yourself into a library first.
As for the actual 3rd party lib, that coding style is very old c style, I’m guessing that library consists of .c files? We have a ticker DEF-3084 which will allow you to compile .c files with clang. In the case of clang (not clang++!), it doesn’t produce this error when compiling a .c file.