ryders@watdcsu.UUCP (07/19/87)
How does one go about writing an assembly function that can be linked
and used by a C program? I have tried several times to get my modules
to link properly but with the end result of "Unresolved external".
I have prefaced the function name with an underscore and I still can't
manage to get my C code to realize that yes, there is an assembly function
by that name in one of the linked modules. HELP!
I'm using MSC 4.0 on an IBM-PC AT.
--
Steve Ryder, Independent Studies, University of Waterloo
Waterloo, Ontario, CANADA, N2L 3G1. (519) 885-1211 Ext. 2352 {allegra,decvax,inhp4,utzoo}!watmath!watdcsu!ryders RYDERS@WATDCSU.UUCP
"Diligence is the mother of good fortune, and idleness, its opposite, never brought a man to the goal of any of his best wishes." -CERVANTES, Don Quixotecramer@kontron.UUCP (Clayton Cramer) (07/21/87)
> How does one go about writing an assembly function that can be linked > and used by a C program? I have tried several times to get my modules > to link properly but with the end result of "Unresolved external". > I have prefaced the function name with an underscore and I still can't > manage to get my C code to realize that yes, there is an assembly function > by that name in one of the linked modules. HELP! > I'm using MSC 4.0 on an IBM-PC AT. > > Steve Ryder, Independent Studies, University of Waterloo The underscore on the function name is necessary, but consider the case. MASM folds all names to uppercase in the symbol table unless you use the /MX option. If your assembler subroutine is named "_foo", and you call it as "FOO" from C, it will work. Clayton E>+ >+ >/B
platt@emory.uucp (Dan Platt) (07/22/87)
In article <3647@watdcsu.waterloo.edu> ryders@watdcsu.UUCP writes: >How does one go about writing an assembly function that can be linked >and used by a C program? I have tried several times to get my modules >to link properly but with the end result of "Unresolved external". >I have prefaced the function name with an underscore and I still can't >manage to get my C code to realize that yes, there is an assembly function >by that name in one of the linked modules. HELP! >I'm using MSC 4.0 on an IBM-PC AT. > From what I can see, the symbol is unsresolved because it is not available to the linker. To make the symbol available to the linker the symbol must be declared as public. The examples in the user's guide show a correct format for making the symbol public. If you missed the 'public', did you make sure that the memory model was correct? How about the calling sequence (saving bp,di and si?) and all the other niggling details? Hope this is a help... Dan
dg@wrs.UUCP (David Goodenough) (07/22/87)
In article <3647@watdcsu.waterloo.edu> ryders@watdcsu.UUCP writes: >How does one go about writing an assembly function that can be linked >and used by a C program? Lots and lots of ranting and raving and mental anguish deleted >I'm using MSC 4.0 on an IBM-PC AT. I rest my case. -- dg@wrs.UUCP - David Goodenough +---+ | +-+-+ +-+-+ | +---+
Rick_R_Kitts@cup.portal.com (07/23/87)
In article <3647@watdcsu.waterloo.edu> ryders@watdcsu.UUCP writes: >How does one go about writing an assembly function that can be linked >and used by a C program? I have tried several times to get my modules >to link properly but with the end result of "Unresolved external". >I have prefaced the function name with an underscore and I still can't >manage to get my C code to realize that yes, there is an assembly function >by that name in one of the linked modules. HELP! >I'm using MSC 4.0 on an IBM-PC AT. > >-- >Steve Ryder, Independent Studies, University of Waterloo > Waterloo, Ontario, CANADA, N2L 3G1. (519) 885-1211 Ext. 2352 >allegra,decvax,inhp4,utzoo}!watmath!watdcsu!ryders RYDERS@WATDCSU.UUC >"Diligence is the mother of good fortune, and idleness, its opposite, never >brought a man to the goal of any of his best wishes." -CERVANTES, Don Quixote Finally _I_ get to help someone out :-) Chances are that you neglected to include the PUBLIC decleration required to access assembler functions form MSC. All functions in MSC are PUBLIC. Below is a bit of code that should help: ********************************************************************** PUBLIC _handler, _setivec, _ptr, _getivec DGROUP GROUP _DATA ASSUME CS:_TEXT, DS:DGROUP, SS:DGROUP,ES:DGROUP _DATA SEGMENT WORD PUBLIC 'DATA' ; If you have any variables that you would like access to in ; C, put them here. If they are declared in C preceed them with ; EXTRN int12 label DWORD off12 DW 0 ; I do not need these in the C seg12 DW 0 ; function, hence no underscores _DATA ENDS _TEXT SEGMENT WORD PUBLIC 'CODE' ; setivec(i_handler, int_number); ; use in Small model _setivec PROC NEAR push bp ; Use these 2 lines for mov bp, sp ; ALL assembly functions mov al, [bp + 4] ;Get the int_number mov ah, 25h ; from the stack push ds lds dx, DWORD PTR [bp + 6] ; Get the address of int 21h ; int_handler from stack pop ds pop bp ; This is also mandatory ret _setivec ENDP ; getivec(); ; Get interupt vector ; _getivec PROC NEAR push bp ; See? mov bp,sp mov ah, 35h mov al, 0Ch ; Hard wired for INT 12 int 21h mov off12, bx ; Store offset and segment mov seg12, es pop bp ret _getivec ENDP _TEXT ENDS END ********************************************************************** sun!cup.portal.com!Rick_R_Kitts ; If you have any variables that
davis@bdmrrr.bdm.com (Arthur Davis x4675) (07/25/87)
You must declare the routines that you wish to access from C as
"public" and preface the routine identifier with an underscore, as}i
in
public _linkroutine
_linkroutine proc {near|far}
That should do it.feg@clyde.ATT.COM (Forrest Gehrke) (07/29/87)
> In article <3647@watdcsu.waterloo.edu> ryders@watdcsu.UUCP writes: > > >How does one go about writing an assembly function that can be linked > >and used by a C program? I have tried several times to get my modules > >to link properly but with the end result of "Unresolved external". > > Write a short C function which includes a couple of declarations. Compile with the assembly language output switch on. The resulting module (having the suffix ".cod") will give you a template of what your assembly language function needs to look like. Pay attention to the entry and exit "housekeeping" assembly language code statements. Forrest Gehrke
steve@nuchat.UUCP (Steve Nuchia) (08/01/87)
In article <3647@watdcsu.waterloo.edu>, ryders@watdcsu.UUCP writes: > How does one go about writing an assembly function that can be linked > and used by a C program? I have tried several times to get my modules > to link properly but with the end result of "Unresolved external". > I have prefaced the function name with an underscore and I still can't > manage to get my C code to realize that yes, there is an assembly function > by that name in one of the linked modules. HELP! > I'm using MSC 4.0 on an IBM-PC AT. First, I suspect you've left off whatever magic phrase tells the assembler that the entry point to your function is a global symbol. Secondly, the method I use when I have to hack up an assembly module for some compiler is to coax it into emitting an assembly source from a C source containing a stub of the routine to be implemented. This way you have a good go-by. Of course this doesn't work if your compiler won't write assembly source; I don't know about MSC 4.0, but I do know that I wouldn't buy a compiler that didn't emit assembly source, no matter how good the debugger is. Steve Nuchia {{soma,academ}!uhnix1,sun!housun}!nuchat!steve