c/4840: compiler error as a result of an inline assembly instruction

[amoroso at gombe dot freeserve dot co dot uk]

>Number:         4840
>Category:       c
>Synopsis:       compiler error as a result of an inline assembly instruction
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    unassigned
>State:          open
>Class:          rejects-legal
>Submitter-Id:   net
>Arrival-Date:   Fri Nov 09 02:46:13 PST 2001
>Closed-Date:
>Last-Modified:
>Originator:     Amoroso Gombe
>Release:        unknown-1.0
>Organization:
>Environment:
Windows 98
>Description:
I get the following compiler error when I use the code fragment below to attempt to do an A/D converter read [or more accurately, transfer the result of the read to an ordinary c variable from within inline assembler]. As you can see, my problem is trying to copy the value sitting in the working register W into an ordinary C variable so I can export the output to stdout [basically be able to see it in the rest of my program somehow!].

 case game_sample:
             port_dir(RG, DIR_ALL_INPUTS);    /*configure port G as an all input port */
             u16_t result asm ("sample") = 0;        /*    <---This is line 106, that the compiler highlights as the error source, but it's syntactically correct. Declares and  Initialises C variable `result', Declares and Initialises assembler variable `sample',  */
    asm volatile("mov w,#0x0AE 
    mov 0x053,w                 /* set adc timer for 100mhz system clock */
    mov w,#0x00F 
              mov 0x052,w       /* configure adc - set AVdd as Vref, right justify result, start read */
              nop                       /* give things a chance to settle down */
              mov w,0x051       /* place result in working register */
              mov sample,w     /* transfer result in working register to sample, so that it is visible to C via `result' */
               "); 
  break;
        }

When I compile the code [it is easily inserted into the template web server cgi script] I get the following error message from the compiler:

/cygdrive/C/starter/app/cgi.c: In function `game_callback':

/cygdrive/C/starter/app/cgi.c: 106: warning: unused variable `result'

/cygdrive/C/starter/app/cgi.c: 106: Internal compiler error in expand _expr, at expr.c:6225    [<---double click and it highlights line 106 pointed to above.]

Please submit a full bug report.

    See <URL:http://www.gnu.org/software/gcc/bugs.html> for instructions.

make.exe: *** [cgi.o] Error 1

Build failed
>How-To-Repeat:

>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: