Line 176 seems to be using a C++ cast (or whatever it is called) which fails to compile when compiling as C code.
The error is reported as:
sinfl.h(176,10): error C2143: syntax error: missing ';' before 'type'
Changing from return int(r); to return (int)r;, or even return r; fixes the error.
BTW, I was glad to find these deflate/inflate libraries that do exactly what I need without having to use libraries that dwarf the size of the rest of my application code. Permissive license is also very much appreciated, Thank you.