Message-Id: <m0wJeTU-000S1vC@natacha.inti.edu.ar>
Comments: Authenticated sender is <salvador AT natacha DOT inti DOT edu DOT ar>
From: "Salvador Eduardo Tropea (SET)" <salvador AT inti DOT edu DOT ar>
Organization: INTI
To: boylesgj AT lion DOT cs DOT latrobe DOT edu DOT au (Gregary J Boyles), djgpp AT delorie DOT com
Date: Tue, 22 Apr 1997 15:31:32 +0000
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Subject: Re: Inline asm macro problem.
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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).

SET
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