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masm output .obj can not be linked with others

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can anyone tell me how to link masm output with other object files. for example main.obj. I am developing a windows kernel mode driver and I want to move inline asm blocks to seperate .asm files for further requirements and prevent further difficulties for example: x64 does not support inline asm. So, i added vm.asm source file to project and from build customization i have selected masm. after that i have selected Microsoft Macro Assembler for Item Type. When i build project vm.obj file has created successfully for vm.asm file. But i cant call asm functions (proc) from C code. It should be link error i think build process not putting obj files together. also i tried with stdcall and cdecl but result is same. my vm.asm: .386 .model flat, C option casemap :none PUBLIC _get_vm _get_vm PROC mov eax, 0101h db 0fh db 01h db 0c1h ret _get_vm endp END here is my c call: ULONG vm_id; extern int _cdecl get_vm(); vm_id = get_vm(); error: project_ddk\main.obj : error LNK2019: unresolved external symbol _get_vm referenced in function _DispatchPnP@8 my ml.exe commandline: ml.exe /c /nologo /safeseh /Zi /Fo"%(FileName).obj" /Fl"" /W3 /errorReport:prompt /Ta assembly build driver linker-error symbol share|improve this question edited Oct 24 '13 at 8:33 asked Oct 24 '13 at 8:15 huyhu 11

Have you tried removing the underscore? –  Michael Oct 24 '13 at 8:38 yes i have tried. but same result. –  huyhu Oct 24 '13 at 9:19 Did you check which symbols your asm file exports? YOu should see the name that the main file expects. –  Devolus Oct 24 '13 at 9:37 @Devolus how can i check it? i mean symbols –  huyhu Oct 24 '13 at 13:30 I don't know which environmont you are using, but if you installed Visual Studio you should have dumpbin which is similar to objdump under Linux. Whith this you can insepct all aspects of your lib/obj files. dumpbin /SYMBOLS your_asm.obj should show you all names. –  Devolus Oct 24 '13 at 14:26 add comment

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Here is some sample that I used to test to link against C (hope it helps). main.cpp: #include <iostream> #include <string.h> #include <windows.h> extern "C" { void PopTest(void); }; int main(int argc, char*arg[]) { PopTest(); return 0; } test.asm .486 .model flat, C option casemap :none .data .code ;*********************** ; ; Just a demo how to declare functions to be used from C ; PopTest PROC push es xor eax,eax push eax pop es pop es mov eax, 2134 push eax mov ebx, [esp] add esp, 04 mov ecx, [esp-4] ret PopTest ENDP END Custom build step in VS2008: D:\Programme\masm32\bin\ml.exe /coff /c test.asm /Fo test.obj copy test.obj Debug\test.obj del test.obj share|improve this answer answered Oct 24 '13 at 9:43 Devolus 8,95131033

thanks for help i have tried like this but no change. how can compile a driver with this external object? my output will be .sys at least –  huyhu Oct 24 '13 at 13:27 Might be that there are different rules for drivers. Did you test with a simple exe file first, if you can call an asm function? Does this also not work, or only if you try to compile a driver? Could be that the link step is different. –  Devolus Oct 24 '13 at 14:28 add comment

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I have never made C functions with masm but in normal procedures you need a text segment, It might need a text segment defined. .386 .model flat, C option casemap :none PUBLIC _get_vm _TEXT SEGMENT _get_vm PROC mov eax, 0101h db 0fh db 01h db 0c1h ret _get_vm endp _TEXT ENDS END EDIT: I just tried to make a simple procedure that works in C, i got this and this works; MASM proc; .386 .model flat, C option casemap :none PUBLIC func _TEXT SEGMENT func PROC mov eax, 2 ret func ENDP _TEXT ENDS END C call; #include <stdio.h> int main(){ int i = 5+func(); printf("%d",i); return 0; } cmd; masm -> ml -c -coff func.asm C -> gcc prog.c func.obj -o main output -> 7