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C–– Compiler
5-21Code Development Tools
Although we have tried to keep the differences between regular C and C– –
to a minimum, there are still a few that require explanation.
5.5.6 Function Prototypes and Declarations
C– – function prototypes and declarations MUST be preceded with the
keyword cmm_func.
Since all functions return through accumulator A0, all functions are of type
integer. The function type may be omitted in the function declaration. If
present, it is ignored anyway. Trying to typecast a function as returning a
pointer will result in a compiler error.
Note: To change a C– – program back into a regular C program (at least from
the point of view of function prototypes and declarations), the following line can
be inserted at the beginning of the C– –program:
#define cmm_func
A library of regular C functions to substitute for the special MSP50C6xx
functions is supplied with the C– – compiler, allowing the user to compare the
results of regular C programs with those of C– –programs. The library is
contained in the C source file cmm_func.c .It should be linked with the C
equivalent of the C– – program, and run in Borland C.
Note:
To use external functions in C– –, a function prototype should be placed in
the file that calls the external function.
5.5.7 Initializations
Due (in part) to the architecture of the MSP50C6xx processors, initialization
is only allowed for global variables. As a side effect, local static variables are
not allowed. For example, a global array can be declared and initialized as
follows:
int int_array[5]={1,2,3,4,5};
Initialization values are stored in program memory.
5.5.8 RAM Usage
RAM location 0 is reserved (and used intensively) by the compiler. The choice
of location 0 does not conflict with the usual definition of a NULL pointer.