Hello,
Poasm v12 can assemble the code below but ml.exe v6.14 and asmc v2.34.50 are reporting the following error message :
Test.asm(9) : error A2005: symbol redefinition : OutputText
How to use correctly ALIAS?
.386
.model flat,stdcall
option casemap:none
ExitProcess PROTO :DWORD
printf PROTO C :DWORD,:VARARG
OutputText PROTO C :DWORD,:VARARG
ALIAS <OutputText>=<printf>
includelib \masm32\lib\kernel32.lib
includelib \masm32\lib\msvcrt.lib
.data
msg db 'Test',0
.code
start:
invoke OutputText,ADDR msg
invoke ExitProcess,0
END start
Hi Vortex
Try something like
OutputText textequ <printf>
Biterider
Hi Biterider,
Thanks but the effect of ALIAS shows itsels during the linker stage, from Pelles C manual :
QuoteThe ALIAS directive creates an alternate name for a procedure (function). This lets you create multiple names for the same procedure, or create libraries that allow the linker to map an old name to a new name. The alias argument specifies the new name, and the actual-name argument specifies the name of an existing procedure. The existing procedure does not have to be defined in the current source file.
Another source :
https://learn.microsoft.com/en-us/cpp/assembler/masm/alias-masm?view=msvc-170
Why not simply invoke 'printf'?
I have tried a couple things including a wrapper procedure...
.386
.model flat,stdcall
option casemap:none
ExitProcess PROTO :DWORD
printf PROTO C :DWORD,:VARARG
OutputText PROTO C :DWORD,:VARARG
includelib \masm32\lib\kernel32.lib
includelib \masm32\lib\msvcrt.lib
.data
msg db 'Test',0
.code
start:
invoke OutputText, ADDR msg
invoke ExitProcess,0
OPTION PROLOGUE:NONE
OPTION EPILOGUE:NONE
OutputText proc C xx:DWORD, args:VARARG
invoke printf, xx
RET
OutputText endp
OPTION PROLOGUE:PrologueDef
OPTION EPILOGUE:EpilogueDef
END start
Why though, if printf works fine by itself?
Have you tried different versions of ml??? I too had no luck with the version in the masm32 Sdk...
Hi sudoku
I am afraid we are not talking about the same thing. How about mapping an old symbol to a new one? Consider this Poasm example :
Test.asm :
.386
.model flat,stdcall
option casemap:none
TerminateApp PROTO :DWORD
OutputText PROTO C :DWORD,:VARARG
includelib \PellesC\lib\Win\kernel32.lib
includelib msvcrt.lib
.data
msg db 'Test',0
.code
start:
invoke OutputText,ADDR msg
invoke TerminateApp,0
END start
Alias.asm :
.386
.model flat,stdcall
option casemap:none
TerminateApp PROTO :DWORD
OutputText PROTO C :DWORD,:VARARG
ALIAS <OutputText>=<printf>
ALIAS <TerminateApp>=<ExitProcess@4>
END
Build.bat :
\PellesC\bin\polib /OUT:msvcrt.lib /MACHINE:x86 /DEF:msvcrt.def
\PellesC\bin\poasm/AIA32 Alias.asm
\PellesC\bin\poasm/AIA32 Test.asm
\PellesC\bin\polink /SUBSYSTEM:CONSOLE Test.obj Alias.obj
The list of weak externals :
\PellesC\bin\podump.exe /symbols Alias.obj
Dump of Alias.obj
File type: OBJ
SYMBOL TABLE
0000 00000001 ABS notype static | @feat.00
0001 00000000 UNDEF notype external | _printf
0002 00000000 UNDEF notype weak external | _OutputText
alternate index 0001, search alias
0004 00000000 UNDEF notype external | _ExitProcess@4
0005 00000000 UNDEF notype weak external | _TerminateApp@4
alternate index 0004, search alias
One you have the list of aliases, no need of TEXTEQUs. This is an example of academic interest.
Hi Vortex, it was just curiosity on my part. I have never used ALIAS and very seldom used textequ.
Have you tried a more recent version of ml?
Hi Vortex
I wasn't aware of this feature.
I tried it with the latest version of UASM
ALIAS <OutputText>=<ConvertNumber>
where ConvertNumber is a real procedure in my code.
The assembler and linker did not complain :cool:
Biterider
Hi sudoku,
Testing with ml.exe v14.29.30152.0 :
Alias.asm(7) : error A2006:undefined symbol : printf
Hi Biterider,
No luck with Uasm :
UASM v2.56, Oct 27 2022, Masm-compatible assembler.
Portions Copyright (c) 1992-2002 Sybase, Inc. All Rights Reserved.
Source code is available under the Sybase Open Watcom Public License.
Alias.asm(7) : Error A2143: Symbol redefinition: OutputText
Alias.asm: 9 lines, 1 passes, 5 ms, 0 warnings, 1 errors
Alias.asm
.386
.model flat,stdcall
option casemap:none
OutputText PROTO C :DWORD,:VARARG
ALIAS <OutputText>=<printf>
END
Hi Vortex
it seems that using invoke directly doesn't work.
The assember doesnt know how to handle AliasProc and even typecasting the call, it produces wrong code (1 indirection)
.code
MyProc proc dParam1:DWORD, dParam2:DWORD
mov eax, dParam1
mov ecx, dParam2
ret
MyProc endp
MyProcType typedef proto :DWORD, :DWORD
ALIAS <AliasProc>=<MyProc>
start proc
int 3
invoke MyProc, 1, 2
invoke MyProcType ptr AliasProc, 3, 4
invoke ExitProcess, 0
start endp
end
What works is a simple (x64)
mov ecx, 3
mov edx, 4
call AliasProc
it jumps to the right location.
Biterider
Hi Vortex
A workaround is
lea xsi, AliasProc
invoke MyProcType ptr xsi, 3, 4
Now it calls the correct procedure, but I think this is not the intended way it should work. :dazzled:
Biterider
I think an ALIAS is a way of letting the linker find a function in an obj file.
It wouldn't make sense to use it the way you are trying, you would just use TEXTEQU
.386
.model flat,stdcall
option casemap:none
ExitProcess PROTO :DWORD
ALIAS <entry_point>=<start>
includelib \masm32\lib\kernel32.lib
.code
start proc public
invoke ExitProcess,0
start endp
END start
Part of the output for dumpbin
COFF SYMBOL TABLE
000 00000000 DEBUG notype Filename | .file
Z:\asm\VORTEX.asm
002 001220FC ABS notype Static | @comp.id
003 00000000 SECT1 notype Static | .text
Section length 7, #relocs 1, #linenums 0, checksum 0
005 00000000 SECT2 notype Static | .data
Section length 0, #relocs 0, #linenums 0, checksum 0
007 00000000 SECT3 notype Static | .drectve
Section length 34, #relocs 0, #linenums 0, checksum 0
009 00000000 UNDEF notype () External | _ExitProcess@4
00A 00000000 UNDEF notype () External | _start@0
00B 00000000 UNDEF notype WeakExternal | _entry_point
Default index A Alias record
00D 00000000 SECT1 notype () External | _start@0
Hi Vortex
There is an example, which might help: rdrand.asm (https://www.veracrypt.fr/code/VeraCrypt/tree/src/Crypto/rdrand_ml.asm?h=VeraCrypt_1.24-Hotfix1&id=61c1baa4bf5a97675187a37cf203e1937a060daa)
;; Fastcall calling conventions exports
ALIAS <@MASM_RDRAND_GenerateBlock@8> = <MASM_RDRAND_GenerateBlock>
ALIAS <@MASM_RDSEED_GenerateBlock@8> = <MASM_RDSEED_GenerateBlock>
Hi
I got it working thanks to Sinsi's hint. :thumbsup:
When building a library, you can use the ALIAS to tell the linker to store an additional (aliased) entry in the .obj file (.lib file).
When you then use your library, and provided you specify a proto for this aliased procedure, the assembler will resolve it correctly.
In the library procedure
ALIAS <AliasProc>=<udword2decA>
In the application
.code
AliasProc proto :POINTER, :DWORD
start proc
local cBuffer[1024]:CHR
invoke udword2decA, addr cBuffer, 123 ;<= original procedure
invoke AliasProc, addr cBuffer, 123 ;<= alias procedure
invoke ExitProcess, 0
start endp
Biterider
Quote from: Biterider on April 04, 2024, 05:40:33 PMHi
I got it working thanks to Sinsi's hint. :thumbsup:
When building a library, you can use the ALIAS to tell the linker to store an additional (aliased) entry in the .obj file (.lib file).
When you then use your library, and provided you specify a proto for this aliased procedure, the assembler will resolve it correctly.
...
Biterider
This is interesting indeed. Indeed this appears to be exactly what Vortex was after. I couldn't for the life of me, figure it out. Now I will have to experiment using this in my sudoku function library. :)
Hello,
Thanks for the replies and the tests. Talking to Nidud (the author of Asmc) about the issue, I received the following reply in his GitHub account :
QuoteAsmc (and Masm) wont allow a direct redefinition of symbols like this. The syntax is:
ALIAS <alias> = <actual-name>
It's possible to use the UNDEF directive here thought:
Nidud's sample code :
.386
.model flat,stdcall
option casemap:none
printf proto c :ptr, :vararg
OutputText proto c :ptr, :vararg
undef OutputText
ALIAS <OutputText>=<printf>
.code
OutputText("%s(%d)\n", __FILE__, __LINE__)
endThanks Nidud. It looks like that only Poasm and Asmc can correctly handle my case.
So I don't get it: why is it so important to be able to redefine symbols? Isn't this just a matter of using a different name for something? Why not just use the original name? Or am I missing something here?
Hi
OLDNAMES.LIB is a good example, here is an explanation from our friend Raymond Chen https://devblogs.microsoft.com/oldnewthing/20200730-00/?p=104021 (https://devblogs.microsoft.com/oldnewthing/20200730-00/?p=104021)
Biterider
I see. It's the old "name game".