The C2000 compiler changed its internal representation of pointers from 22 bits to 32 bits around version 6.4.0. When encountering 22-bit pointer types, these recent compilers silently convert them to 32-bit types, and everything is usually fine. The problem here is with a qualified pointer type -- "float * volatile" -- where the pointer type itself is qualified, not the type pointed to. Qualified 22-bit pointer types are not properly converted to 32 bits. Normally that's no problem, because recent compilers will not produce 22-bit pointer types to worry about. However, libraries may have compiler internal representations embedded within them, for use when compiling with --opt_level=4. If the library is old enough, it may have been compiled with a pre-6.4.x compiler and thus have 22-bit pointers. At the .obj level, those aren't visible, but --opt_level=4 uses the embedded internal representation and then they're apparent. This problem requires all these elements: 1. Library compiled with compiler older than 6.4.0. 2. Library contains embedded internal representation. 3. Library uses qualified pointers, eg, "float * volatile" or "int * const". 4. Project is compiled with --opt_level=4. 5. Project compiler is 18.1.x or newer. The troublesome library in this case is SFRA_IQ_Lib.lib, which was compiled with version 6.2.8.