BL51: '*** WARNING L1: UNRESOLVED EXTERNAL SYMBOL'

On 5/10/06 8:24:01; erik malund wrote:
>
> Many decide to ignore warnings, that may be OK during
> development, but there is a difference between "ignore" and
> "not read"
>
> I may ignore warnings during development, but I ALWAYS read
> them
>
Ok, so oversimplified my process. I read ALL the warnings
the first time I link a new module and take action as
indicated. But some of them are not eliminatable.

Thereafter I only read the body of the warnings if the
NUMBER of warnings changes from the prior build. In the
case cited, I went too fast and confused "UNRESOLVED" with
"UNCALLED".

Then at 5/10/06 8:23:07; A.W. Neil wrote:
>
> How about If you were doing some sort of "incremental
> build", or you were building a Library that required some
> call-backs to be provided by the user?
>
Ok, I'll grant you that scenario. It's just that I've never
used it.

>
> Anyhow, if the functions in those modules are never called,
> and the data is never accessed, what difference does it
> make!
>
<snip>
>
> As soon as you actually try to reference one of the
> undefined symbols, that most certainly will give you an
> error.
>
Well, you want the dirty details, here they are. The source
containing the main() function looks like (names have been
changed to protect the guilty):

while(1) {
  for(j=0; j<6; j++) {   | ?C0001: CLR     A        ;  1
                         |         MOV     j,A      ;  2
                         |         MOV     j+01H,A  ;  3
                         | ?C0003: CLR     C        ;  4
                         |         MOV     A,j+01H  ;  5
                         |         SUBB    A,#06H   ;  6
                         |         MOV     A,j      ;  7
                         |         SUBB    A,#00H   ;  8
                         |         JNC     ?C0001   ;  9
    doFoo(2, j);         |         MOV     R5,j+01H ; 10
                         |         MOV     R7,#02H  ; 11
                         |         LCALL   _doFoo   ; 12
    wait(4473);          |         MOV     R7,#079H ; 13
                         |         MOV     R6,#011H ; 14
                         |         LCALL   _wait    ; 15
  }                      |         INC     j+01H    ; 16
                         |         MOV     A,j+01H  ; 17
                         |         JNZ     ?C0007   ; 18
                         |         INC     j        ; 19
                         | ?C0007: SJMP    ?C0003   ; 20
                         |         RET              ; 21
} /* END while(1) */     |                          ; 22

I tacked the assembly produced by C51 onto the right side
for reasons that will become apparent later. I also added
line numbers to facilitate discussion. Variable j is an
unsigned int.

The module I forgot to add holds function wait() (which is a
thumb-twiddling loop whose execution time I can control with
the argument shown). The object module produced by the
compiler sets wait()'s address to dummy value c:0x0000
(a.k.a. your friendly neighborhood power-up vector).

The linker issues its warning:

*** WARNING L2: REFERENCE MADE TO UNRESOLVED EXTERNAL
    SYMBOL:  _WAIT
    MODULE:  TestFoo.obj (TESTFOO)
    ADDRESS: 01BEH

and the execution module gets built, assuming wait() is
still at 0000.

As compiled, the "j=0" part of the for-loop consists of the 3
instructions beginning at line 1; the "j<6" code is in
lines 4-9, while the "j++" term resides in lines 16-19.

This baby executes exactly as I intended until we get to the
call to wait(). At this point, it performs the moral
equivalent of a power-on reset, putting control back at the
top of the loop with j=0. Thus my program executes the
infinite loop I had wanted, but j never deviates from 0.

This is the scenario that prompted this post.

============================================================
Gary Lynch            |     To send mail, change no$pam in
lynchg@no$pam.com     |     my domain name to stacoenergy

On 5/10/06 8:24:01; erik malund wrote:
>
> Many decide to ignore warnings, that may be OK during
> development, but there is a difference between "ignore" and
> "not read"
>
> I may ignore warnings during development, but I ALWAYS read
> them
>
Ok, so oversimplified my process. I read ALL the warnings
the first time I link a new module and take action as
indicated. But some of them are not eliminatable.

Thereafter I only read the body of the warnings if the
NUMBER of warnings changes from the prior build. In the
case cited, I went too fast and confused "UNRESOLVED" with
"UNCALLED".

Then at 5/10/06 8:23:07; A.W. Neil wrote:
>
> How about If you were doing some sort of "incremental
> build", or you were building a Library that required some
> call-backs to be provided by the user?
>
Ok, I'll grant you that scenario. It's just that I've never
used it.

>
> Anyhow, if the functions in those modules are never called,
> and the data is never accessed, what difference does it
> make!
>
<snip>
>
> As soon as you actually try to reference one of the
> undefined symbols, that most certainly will give you an
> error.
>
Well, you want the dirty details, here they are. The source
containing the main() function looks like (names have been
changed to protect the guilty):

while(1) {
  for(j=0; j<6; j++) {   | ?C0001: CLR     A        ;  1
                         |         MOV     j,A      ;  2
                         |         MOV     j+01H,A  ;  3
                         | ?C0003: CLR     C        ;  4
                         |         MOV     A,j+01H  ;  5
                         |         SUBB    A,#06H   ;  6
                         |         MOV     A,j      ;  7
                         |         SUBB    A,#00H   ;  8
                         |         JNC     ?C0001   ;  9
    doFoo(2, j);         |         MOV     R5,j+01H ; 10
                         |         MOV     R7,#02H  ; 11
                         |         LCALL   _doFoo   ; 12
    wait(4473);          |         MOV     R7,#079H ; 13
                         |         MOV     R6,#011H ; 14
                         |         LCALL   _wait    ; 15
  }                      |         INC     j+01H    ; 16
                         |         MOV     A,j+01H  ; 17
                         |         JNZ     ?C0007   ; 18
                         |         INC     j        ; 19
                         | ?C0007: SJMP    ?C0003   ; 20
                         |         RET              ; 21
} /* END while(1) */     |                          ; 22

I tacked the assembly produced by C51 onto the right side
for reasons that will become apparent later. I also added
line numbers to facilitate discussion. Variable j is an
unsigned int.

The module I forgot to add holds function wait() (which is a
thumb-twiddling loop whose execution time I can control with
the argument shown). The object module produced by the
compiler sets wait()'s address to dummy value c:0x0000
(a.k.a. your friendly neighborhood power-up vector).

The linker issues its warning:

*** WARNING L2: REFERENCE MADE TO UNRESOLVED EXTERNAL
    SYMBOL:  _WAIT
    MODULE:  TestFoo.obj (TESTFOO)
    ADDRESS: 01BEH

and the execution module gets built, assuming wait() is
still at 0000.

As compiled, the "j=0" part of the for-loop consists of the 3
instructions beginning at line 1; the "j<6" code is in
lines 4-9, while the "j++" term resides in lines 16-19.

This baby executes exactly as I intended until we get to the
call to wait(). At this point, it performs the moral
equivalent of a power-on reset, putting control back at the
top of the loop with j=0. Thus my program executes the
infinite loop I had wanted, but j never deviates from 0.

This is the scenario that prompted this post.

============================================================
Gary Lynch            |     To send mail, change no$pam in
lynchg@no$pam.com     |     my domain name to stacoenergy