Mail Archives: djgpp/1997/04/22/14:41:48
boylesgj AT lion DOT cs DOT latrobe DOT edu DOT au (Gregary J Boyles) wrote:
> I have the following macro which I am using in an ISR.
>
> #define INPORTB(Port,Byte) asm volatile ( \
> "\ninb %1,%%al\n" \
> "movb %%al,%0\n" \
> : "=g"(Byte) \
> : "g"(Port) \
> : "memory","al" \
> )
> Inside the ISR I have two variables : KeyBoardPort and ScanCode.
>
> I want to call the macro as follows : INPORTB(KeyBoardPort,ScanCode).
>
> The problem is that the macro expands to : inb -4(%ebp),%al; movb %al,-9(%ebp);
> and the first argument of inb ends up as a non literal which causes the error
> messages below.
>
> There must be a way around this because I can happily pass KeyBoardPort to
> the dos library function inportb(...).
>
> Can any one help me out?
1) Isn't DJGPP generating the right code when you use the library functions?
(use -O2 or at least -O).
2) Why KeyBoardPort is a variable instead of a constant? do you plan to modify
the value?!
3) The problem is that you are using the g constraint so the code generated is
right, take a look to the Brennan's page he explains the meaning of these
constraints, or look in other related pages. You can find a link to it in my
pages (see the signature).
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