Yes, and it's a pretty common situation.   The fopen() that I call within a DLL may not be the same fopen() called by another DLL.  When writing a DLL for Windows, the API must be designed with the assumption that anything returned by the C library cannot be passed a different C library.  For example, suppose I a expose a function in my DLL that allocates some memory, populates it with useful information, and returns a pointer.  I must also supply a function to free the memory.  I cannot ask the caller to simply call free(), because their free() may not be using the same heap as my malloc(). 

Likewise, a FILE * isn't safe to pass around, unless I can guarantee that the application really is one big happy family compiled against the same version of the C library.