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Index > High Level Languages > interface C-ASM

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alessandro95



Joined: 24 Mar 2013
Posts: 62
alessandro95
I started studying C recently, using gcc as compiler, but I found out that it uses AT&T syntax for inline ASM, which is simply horrible!

So I would like to write my ASM functions in a file and then call them from another C file, anyone knows how to do that?
I think I read something about this in the forum but I cannot find it anymore...

Thank in advance!
Post 03 May 2013, 01:40
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Bob++



Joined: 12 Feb 2013
Posts: 92
Bob++
Currently gcc supports intel's assembly syntax. Not only output it,inline too.
Put this
Code:
.intel_syntax noprefix    
before intel's assembly,and use
Code:
-masm=intel    
.
But don't forget to switch back to ATT's assembly after:
Code:
.att_syntax noprefix    


EDIT:

To use non-inline assembly routines with gcc,it's very simple. Make you assembly generate objcode(on FASM,see "format" section from fasm's documentation) code and then compile with gcc to an executable as following:
Code:
gcc foo.o etc.c -o exe    
Post 03 May 2013, 01:54
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alessandro95



Joined: 24 Mar 2013
Posts: 62
alessandro95
Thanks a lot for the fast answer, I prefer to use non-inline assembly so I have some other questions:

Should the assembly routines have some particular name? (begin with underscore or something)

How do I pass parameters?

And if there is a return value where should it be?

The compiler deals with the values of registers or my routines should worry about restoring them?

If you could make me a very basic example, a function that adds two values and return the sum or something like that, I would find it truly useful since I know really a little of C!
Thank again!
Post 03 May 2013, 02:14
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TmX



Joined: 02 Mar 2006
Posts: 821
Location: Jakarta, Indonesia
TmX
Maybe you'd like to try this:
http://www.flatassembler.net/examples/msvc.zip

Very Happy
Post 03 May 2013, 02:26
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alessandro95



Joined: 24 Mar 2013
Posts: 62
alessandro95
That does look exactly what I was searching for, thanks a lot!

I'll look at this files, I'll post here again in case I still have some doubts Smile
Post 03 May 2013, 02:30
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