Including a C header file using macros ?

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wht36

Joined: 18 Sep 2005
Posts: 106

wht36 11 Nov 2008, 01:25

Is there a way to include a C header file and then use preprocessor or assembler directives to convert the function prototypes (into some kind of import list) and/or constants? I tried to do it but there is a problem with parsing // comments.

The load and store assembler directives does not work (I think because they only work on already assembled bytes, and // cannot be assembled).

For example the code below gives 'illegal instruction' error.

Code:

virtual at test1
  repeat test2-test1
          load A byte from %-1
                load B byte from %
          if A='/' & B='/'
                    store byte ';' at %-1
             else
                        store byte A at %-1
         end if
      end repeat
end virtual

test1:
include 'test1.c'
test2:

where test1.c looks like this

Code:

// sample test file
     mov bx,1

The 'fix' directive also does not work because it does not accept '//' as a proper thing to patch and throws an illegal instruction error as well.

So is there anyway out of this predicament? Unless I use FASM to generate a cleaned up file from the header file and include that instead?

11 Nov 2008, 01:25

baldr

Joined: 19 Mar 2008
Posts: 1651

baldr 11 Nov 2008, 10:04

wht36,

Is your goal is a fasm source that compiles to some other fasm source with constants, structures and some kind of prototypes for functions from given C source? For it's impossible to write self-modifying source in fasm AFAIK.

Pretty challenging, interpret C source with fasm script…

Your problem with // comments may be solved as follows:

Code:

format binary as "c.fasm"
file "test.c"
in_comment = 0; are we in // comment? Not yet.
repeat $ - $$
    load c byte from $$+%-1
    if in_comment
        if c = 10; LF
            in_comment = 0; single-line comment ends here
        end if
    else
        if (c = '/') & ($$+% < $); got slash and it's not last character in file
            load c byte from $$+%; or else we'll got error here
            if c = '/'; got two slashes
                store byte ';' at $$+%-1; replace first slash with semicolon
                in_comment = 1; and set flag to ignore everything up to LF
            end if
        end if
    end if
end repeat

11 Nov 2008, 10:04

wht36

Joined: 18 Sep 2005
Posts: 106

wht36 11 Nov 2008, 15:59

baldr wrote:

wht36,

Is your goal is a fasm source that compiles to some other fasm source with constants, structures and some kind of prototypes for functions from given C source?

Yes, that is my goal. Initially I considered writing a specific EXE program to convert C prototypes into fasm macros (possibly with type checking), but I should try to do it with macros, since I'm trying to learn macros.

Thanks very much for your code! I was struggling with range errors and couldn't quite figure out how to avoid them! I guess the only way to change "//" into ";/" is to load the file as a binary file and to replace with assembler directives. Oh well, I could always use a batch file to run fasm twice to parse the output again. Many thanks!

11 Nov 2008, 15:59

baldr

Joined: 19 Mar 2008
Posts: 1651

baldr 11 Nov 2008, 17:08

wht36,

My example didn't use macros. Just assembler directives. It's possible to write such a script to replace "//" with ";" (not just ";/"), but it will be complex and hard to understand. Now imagine that you're trying to handle /* */ comments as well… Hell of a scripting, almost implementing C syntax parser (with regards to C preprocessor also)… Doesn't it undermine the goal?

Standalone program will fit the bill much more accurately.

There was attempts to use C preprocessor for preprocessing fasm sources with #includes of C header files. Unluckily, it will replace RT_CURSOR with something like (LPSTR)((ULONG_PTR)((WORD)(1))), tasty bit for fasm's error handler…

11 Nov 2008, 17:08

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