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call an ASM function from a C function

gouezel yann

I wrote a C extension file program where my function is declared with C langage with parameters and writen in ASM langage:

int MyFunc(int param1, int param2)
{
#asm
...
...
#endasm
}

From other files, the call is working but I have WARNING in compilation of my assembly file on param1 and param2 because I don't use them directly but I use register R4 to R7.

The program is working but I don't understand how can I write the program to don't have any warning.

Parents
  • 0 in reply to gouezel yann

    First you have to set up some kind of fake C file... here I will call it "xxx_prot.c" because you only set up kind of function skeletons.

    It looks like this:
    xxx_prot.c:
    #pragma SRC

    unsigned char func1( unsigned char parameter ) {
    unsigned char loc_var_func1; // some local variable

    loc_var_func1 = 0;
    return loc_var_func1;
    }

    void func2( void ) {
    }

    Then you compile this file (the SRC pragma is important). Instead of an object file, you get a file called xxx_prot.src.

    It is an assembler program and looks looks like this:
    NAME XXX_PROT

    ?PR?_func1?XXX_PROT SEGMENT CODE
    ?XD?_func1?XXX_PROT SEGMENT XDATA OVERLAYABLE
    ?PR?func2?XXX_PROT SEGMENT CODE
    PUBLIC func2
    PUBLIC _func1

    RSEG ?XD?_func1?XXX_PROT
    ?_func1?BYTE:
    parameter?040: DS 1
    ; #pragma SRC
    ;
    ; unsigned char func1( unsigned char parameter ) {

    RSEG ?PR?_func1?XXX_PROT
    _func1:
    USING 0
    MOV DPTR,#parameter?040
    MOV A,R7
    MOVX @DPTR,A
    ; SOURCE LINE # 3
    ; unsigned char loc_var_func1; // some local variable
    ;
    ; loc_var_func1 = 0;
    ; SOURCE LINE # 6
    ;---- Variable 'loc_var_func1?041' assigned to Register 'R7' ----
    CLR A
    MOV R7,A
    ; return loc_var_func1;
    ; SOURCE LINE # 7
    ; }
    ; SOURCE LINE # 8
    ?C0001:
    RET
    ; END OF _func1

    ;
    ; void func2( void ) {

    RSEG ?PR?func2?XXX_PROT
    func2:
    ; SOURCE LINE # 10
    ; }
    ; SOURCE LINE # 11
    RET
    ; END OF func2

    END

    As you can see the parameters are commented and the required segments already have the right names and what
    you need to be imported by other c-files is declared public.

    You can copy this into your destination assembler file (e.g. xxx.a51) and "fill in" your code.

    Then you write a header file (e.g. xxx.h), like if you would do that for the xxx_prot.c.

    That's it. It is not very difficult. I woudl recommend to name the "prototype c file" different from the actual assembler file.

Reply
  • 0 in reply to gouezel yann

    First you have to set up some kind of fake C file... here I will call it "xxx_prot.c" because you only set up kind of function skeletons.

    It looks like this:
    xxx_prot.c:
    #pragma SRC

    unsigned char func1( unsigned char parameter ) {
    unsigned char loc_var_func1; // some local variable

    loc_var_func1 = 0;
    return loc_var_func1;
    }

    void func2( void ) {
    }

    Then you compile this file (the SRC pragma is important). Instead of an object file, you get a file called xxx_prot.src.

    It is an assembler program and looks looks like this:
    NAME XXX_PROT

    ?PR?_func1?XXX_PROT SEGMENT CODE
    ?XD?_func1?XXX_PROT SEGMENT XDATA OVERLAYABLE
    ?PR?func2?XXX_PROT SEGMENT CODE
    PUBLIC func2
    PUBLIC _func1

    RSEG ?XD?_func1?XXX_PROT
    ?_func1?BYTE:
    parameter?040: DS 1
    ; #pragma SRC
    ;
    ; unsigned char func1( unsigned char parameter ) {

    RSEG ?PR?_func1?XXX_PROT
    _func1:
    USING 0
    MOV DPTR,#parameter?040
    MOV A,R7
    MOVX @DPTR,A
    ; SOURCE LINE # 3
    ; unsigned char loc_var_func1; // some local variable
    ;
    ; loc_var_func1 = 0;
    ; SOURCE LINE # 6
    ;---- Variable 'loc_var_func1?041' assigned to Register 'R7' ----
    CLR A
    MOV R7,A
    ; return loc_var_func1;
    ; SOURCE LINE # 7
    ; }
    ; SOURCE LINE # 8
    ?C0001:
    RET
    ; END OF _func1

    ;
    ; void func2( void ) {

    RSEG ?PR?func2?XXX_PROT
    func2:
    ; SOURCE LINE # 10
    ; }
    ; SOURCE LINE # 11
    RET
    ; END OF func2

    END

    As you can see the parameters are commented and the required segments already have the right names and what
    you need to be imported by other c-files is declared public.

    You can copy this into your destination assembler file (e.g. xxx.a51) and "fill in" your code.

    Then you write a header file (e.g. xxx.h), like if you would do that for the xxx_prot.c.

    That's it. It is not very difficult. I woudl recommend to name the "prototype c file" different from the actual assembler file.

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