Author Topic: having difficulty with extern  (Read 3583 times)

ggmasm32

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having difficulty with extern
« on: September 18, 2015, 04:46:29 AM »
Ok, I hope this is the last major question I have here after putting low of rudimentary question. I tried to do a correct usage of extern and public in two different files and both of them compiles and generates obj files but during link the proc declared as public (lib.asm) and imported into second file (asmfile.asm) with extern directive is causing issue. I re-checked everything and corrected but still it is giving a grief. Can someone help on this?

After compilation, I am not sure if the code segment of lib.asm were included in the binary (need to check that) but for sure, data segment of lib.asm was included by dumping the area with debugger.

Thanks in advance!

C:\git\minix.dev>dir
 Volume in drive C has no label.
 Volume Serial Number is FC76-C34F

 Directory of C:\git\minix.dev

09/17/2015  10:43 PM    <DIR>          .
09/17/2015  10:43 PM    <DIR>          ..
09/18/2015  12:05 AM    <DIR>          exp
               0 File(s)              0 bytes
               3 Dir(s)  46,058,704,896 bytes free

C:\git\minix.dev>cdexp

C:\git\minix.dev\exp>dir
 Volume in drive C has no label.
 Volume Serial Number is FC76-C34F

 Directory of C:\git\minix.dev\exp

09/18/2015  12:05 AM    <DIR>          .
09/18/2015  12:05 AM    <DIR>          ..
09/17/2015  11:53 PM               941 asmfile.asm
09/18/2015  12:05 AM               882 asmfile.exe
09/18/2015  12:05 AM             3,750 asmfile.lst
09/18/2015  12:05 AM               320 asmfile.map
09/18/2015  12:05 AM               718 asmfile.obj
09/17/2015  10:43 PM               240 cfile.c
09/17/2015  10:43 PM                44 del1.bat
09/17/2015  11:50 PM               524 lib.asm
09/17/2015  10:43 PM               239 lib.inc
09/18/2015  12:05 AM             1,844 lib.lst
09/18/2015  12:05 AM               537 lib.obj
09/17/2015  10:43 PM               599 macros.inc
09/17/2015  11:37 PM               194 masm.cmpl.bat
              13 File(s)         10,832 bytes
               2 Dir(s)  46,058,704,896 bytes free

C:\git\minix.dev\exp>typeasmfile.asm
.586
;.model flat, stdcall

    include macros.inc

extern   extFnc:near
;extrn   extFcn1:near

sta segment para stack use16 'stack'
    db 100h dup(0)
sta ends

data segment para public 'data'
    str0    db 'test string in asmfile.asm$'
    str1    db 'str1$'
data ends

code segment para public use16 'code'
assume cs:code, ds:data,ss:sta

main    proc    far
    mov     ax, DATA
    mov     ds, ax

;    PRINTF  "macrostring"
;    PRINTF  "2ndMacroString"

;   call    extFcn

;   lea     bp, str0
;   call    printStr

    mov     ax, 4c00h
    int     21h

    main    endp

;   input
;   DS:BP   - pointer to string ($) terminated.

printStr    proc    far
printLoop:
    mov     dl, ds:[bp]
    cmp     dl, '$'
    je      quit
    mov     ah, 02h
    int     21h
    inc     bp
    jmp     printLoop
quit:
    ret

printStr    endp

code    ends
    end     main







C:\git\minix.dev\exp>typelib.asm
.586
public  extFcn, extFcn1

sta segment para stack use16 'stack'
sta ends

data segment para public 'data'
    str1    db 'test string in lib.asm'
data ends

code segment    para public use16 'code'
assume cs:code, ds:code, ss:sta

extFcn1 proc    near
    xor     dl, dl
    mov     dl, 36h
    mov     ah, 02h
    int     21h
    ret
extFcn1 endp

extFcn  proc    near
    xor     dh, dh
    mov     dl, 35h
    mov     ah, 02h
    int     21h
    ret
extFcn  endp
code    ends
        end

C:\git\minix.dev\exp>del1.bat

C:\git\minix.dev\exp>del *.obj

C:\git\minix.dev\exp>del *.exe

C:\git\minix.dev\exp>del *.lst

C:\git\minix.dev\exp>del *.map

C:\git\minix.dev\exp>masm.cmpl.bat

C:\git\minix.dev\exp>del *.exe
Could Not Find C:\git\minix.dev\exp\*.exe

C:\git\minix.dev\exp>del *.obj
Could Not Find C:\git\minix.dev\exp\*.obj

C:\git\minix.dev\exp>del *.lst
Could Not Find C:\git\minix.dev\exp\*.lst

C:\git\minix.dev\exp>del *.map
Could Not Find C:\git\minix.dev\exp\*.map

C:\git\minix.dev\exp>rem ml /c /coff /Cp /Fm /Fl  asmfile.asm

C:\git\minix.dev\exp>rem ml /omf /c /Fl /Zi /Zd lib.asm

C:\git\minix.dev\exp>ml /c /Fl /Zi /Zd asmfile.asm lib.asm
Microsoft (R) Macro Assembler Version 6.14.8444
Copyright (C) Microsoft Corp 1981-1997.  All rights reserved.

 Assembling: asmfile.asm
sta segment para stack use16 'stack'ends                                    data segment para public 'data'    str1    db 'test string in lib.asm'data ends                                       code segment    para public use16 'code'assume cs:code, ds:code, ss:sta                                        extFcn1 proc    near    xor     dl, dl  mov     dl, 36hah, 02int     21h    ret        extFcn1 endp            extFcn  proc    near    xor     dh, dh  mov     dl, 35hah, 02int     21h    ret        extFcn  endpcode    ends        end    C:\git\minix.dev\exp>del1.bat                             C:\git\minix.dev\exp>del *.obj                              C:\git\minix.dev\exp>del *.exe                              C:\git\minix.dev\exp>del *.lst                              C:\git\minix.dev\exp>del *.map                              C:\git\minix.dev\exp>masm.cmpl.bat                                  C:\git\minix.dev\exp>del *.exeould Not Find C:\git\minix.dev\exp\*.exe                                         C:\git\minix.dev\exp>del *.objould Not Find C:\git\minix.dev\exp\*.obj                                         C:\git\minix.dev\exp>del *.lstould Not Find C:\git\minix.dev\exp\*.lst                                         C:\git\minix.dev\exp>del *.mapould Not Find C:\git\minix.dev\exp\*.map                                         C:\git\minix.dev\exp>rem ml /c /coff /Cp /Fm /Fl  asmfile.asm                                                             C:\git\minix.dev\exp>rem ml /omf /c /Fl /Zi /Zd lib.asm                                                       C:\git\minix.dev\exp>ml /c /Fl /Zi /Zd asmfile.asm lib.asmMicrosoft (R) Macro Assembler Version 6.14.8444           Copyright (C) Microsoft Corp 1981-1997.  All rights reserved.                                                             Assembling: asmfile.asmlib.asm   
C:\git\minix.dev\exp>link16 asmfile.obj lib.obj,,,,,

Microsoft (R) Segmented Executable Linker  Version 5.60.339 Dec  5 1994
Copyright (C) Microsoft Corp 1984-1993.  All rights reserved.


asmfile.obj(asmfile.asm) : error L2029: 'extFnc' : unresolved external


There was 1 error detected

C:\git\minix.dev\exp>

dedndave

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Re: having difficulty with extern
« Reply #1 on: September 18, 2015, 06:31:07 AM »
ok - i don't have any experience using masm 6.x + with 16-bit libraries - lol

the last time i wrote libs/eternal objs for 16-bit, i was using masm 5.10 and a linker from the same era

but, i have written a little static library example using 6.x, for 32-bit code
seems like the directives should also work for 16-bit code

first, i notice that you are creating your own segments, like we did in the old days
that's a lot of work - lol
but, it should be do-able
easier to use:
.STACK 4096 for 4 KB stack (as an example)
.DATA for initialized data
.DATA? for uninitialized data
.CONST for read-only initialized data
.CODE for code
@Data to load DGROUP into a register

no more text segment para blah blah blah
no more ENDS, either - when you open another segment, the current one is closed

that having been said, i will find the 32-bit example for you to look at
you can throw out EXTRN and PUBLIC, and just use EXTERNDEF for both   :P

dedndave

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Re: having difficulty with extern
« Reply #2 on: September 18, 2015, 06:33:37 AM »
PROC's are public, by default (unless you specify PRIVATE on the PROC line)

http://masm32.com/board/index.php?topic=2743.msg29054#msg29054

dedndave

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Re: having difficulty with extern
« Reply #3 on: September 18, 2015, 06:41:24 AM »
one thing i see....
if you are assembling 16-bit code, you want an OMF format object module
Code: [Select]
ml /c /omf .......

ggmasm32

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Re: having difficulty with extern
« Reply #4 on: September 18, 2015, 10:05:09 AM »
yes this is the way i have been coding with half decado ago and moved to something else.
Now my skillset is stuck with this old way programmiing.
For the project, it does not matter which one you use.

ggmasm32

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Re: having difficulty with extern
« Reply #5 on: September 18, 2015, 10:06:34 AM »
ok - i don't have any experience using masm 6.x + with 16-bit libraries - lol

the last time i wrote libs/eternal objs for 16-bit, i was using masm 5.10 and a linker from the same era

but, i have written a little static library example using 6.x, for 32-bit code
seems like the directives should also work for 16-bit code

first, i notice that you are creating your own segments, like we did in the old days
that's a lot of work - lol
but, it should be do-able
easier to use:
.STACK 4096 for 4 KB stack (as an example)
.DATA for initialized data
.DATA? for uninitialized data
.CONST for read-only initialized data
.CODE for code
@Data to load DGROUP into a register

no more text segment para blah blah blah
no more ENDS, either - when you open another segment, the current one is closed

that having been said, i will find the 32-bit example for you to look at
you can throw out EXTRN and PUBLIC, and just use EXTERNDEF for both   :P

will externdef will work for both in the current style of programming? I will give it a try. thanks.,  ;)

dedndave

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Re: having difficulty with extern
« Reply #6 on: September 18, 2015, 10:53:26 AM »
what you have may work - but the OBJ is not recognized because it's not OMF format

ggmasm32

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Re: having difficulty with extern
« Reply #7 on: September 18, 2015, 11:40:11 AM »
great, using externdef it worked. I had to declare inside the cseg in order for it work. I am not sure why public and extern did not work.
Tutorial says externdef will either act like extern or public depending whether the symbol exists in the file or not.
If so, only logical reason it did not work is might be public/extern was declared outside the cseg. That is what the online tutorial shows. Might that was typo?
Who knows.

ggmasm32

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Re: having difficulty with extern
« Reply #8 on: September 18, 2015, 02:56:46 PM »
saying that have good idea: macro the crap out of extern statements so that when the files to be compiled reached dozens or hundreds no forgotten external reference compile error:

EXTERN1 MACRO
    EXTERNDEF Var1
    EXTERNDEF Var2
    EXTERNDEF ...
    EXTERNDEF Var100
ENDM

so that any functions needs to be externalized just include in this macro.
Good?

dedndave

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Re: having difficulty with extern
« Reply #9 on: September 18, 2015, 03:13:16 PM »
if EXTERNDEF refers to something external, you should provide a type
Code: [Select]
    EXTERNDEF  wSomeWord:WORD
    EXTERNDEF  bSomeByte:BYTE
    EXTERNDEF  sSomeStruct:STRUCTNAME
    EXTERNDEF  fSomeProc:NEAR    ;or FAR

if the symbol is internal, just the symbol name is required

ggmasm32

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Re: having difficulty with extern
« Reply #10 on: September 19, 2015, 07:41:07 AM »
yes i noticed, however i just included in the macro as externdef proc1:near etc., it does not seem to hurt (compiler did not complain) when used as a public statement too.
So the potential benefit seems to outweight to avoid maintenance nightmare of keeping track of all externdef variable, functions etc.,
Just declare the macro in your new module and every externdef is included.
Anything add to be used externally, just add to macro.
Might not be a big deal when having a few files, but when you have 100 files.

rrr314159

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Re: having difficulty with extern
« Reply #11 on: September 19, 2015, 01:08:29 PM »
hi ggmasm32,

FWIW, there's no particular reason to use a macro. Normally we just put all the externdef's in an include file, and include that file at the top of each module. Using a macro as you do, it still must be in an include file, which still must be included, plus you then have to invoke the macro. Only advantage, if you want to include the file for other reasons, but not the externdef's, you can not invoke the macro; but that doesn't seem too useful. So, you can just skip the "EXTERN1" macro definition
I am NaN ;)

sinsi

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Re: having difficulty with extern
« Reply #12 on: September 19, 2015, 01:34:39 PM »
You can also have more than one per line
Code: [Select]
EXTERNDEF proc1:near, var1:dword
I can walk on water but stagger on beer.

ggmasm32

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Re: having difficulty with extern
« Reply #13 on: January 18, 2016, 08:50:02 PM »
bringing up this old thread, the externdef has worked great with functions. However, I am having issue with making serial byte string as external

externdef does not work.

if variable is declared as

var1 db 10h dup (?)

i could not figure out how to make it external??

so far tried with 2 ways:

1. externdef var1:byte in all files. (does not work)

2. public var1 in file in which it is declared
    and extrn var1:byte in which it is used.

For both instances, I got fixup overflow during link. ?? thx




dedndave

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Re: having difficulty with extern
« Reply #14 on: January 19, 2016, 12:54:47 AM »
perhaps the name "var1" is used elsewhere ?

i haven't written any 16-bit libraries for years, so don't have to ready example
but, the one you tried looks ok

in the file where SomeBytes is defined:
Code: [Select]
    public  SomeBytes
in the file where SomeBytes is referenced:
Code: [Select]
    extrn   SomeBytes:BYTE
it would be helpful if you posted examples
i don't have time to create a 16-bit lib example from scratch