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Help me with C++ 2 alternatives with Turbo C (malloc/bgiobj) (Developers)

posted by Arjay, 22.06.2010, 14:19
(edited by Arjay on 22.06.2010, 16:10)

> My problem is that need making to ensure to me that several variables
> remain together in the executable file (.exe) or when running are located
> together in the same segment.
> For example:
> int a; SEG=0 OFFSET=0
> int b; SEG=0 OFFSET=2
> int c; SEG=0 OFFSET=4
> In assembler I can control this but in C++ is possible?
> Thanks
 In addition to using struct/TC alternatives which have already been covered. There are at least 2 other alternatives using TC that sprung to mind:

1) Don't hard-code in your resources (e.g. like you did with the ASM version) and instead use malloc - this has the advantage your resources can easily be changed by others particularly if you pack them in as a common data format, e.g. On an unreleased DOS game I wrote all the code to use the Windows .FNT/.FON file format and various graphics formats. There are however now a lot of free graphics libraries out there that you could easily incorporate. Certainly storing resources such as text non-hardcoded always helps translators.

2) Use BGIOBJ as it is known as with Turbo C (or BINOBJ as it has also been known, e.g. with Turbo Pascal). For example:

bgiobj mydata.bin mydata.obj mydata

Once a file has been converted with BGIOBJ/BINOBJ you can then include the .OBJ file at link time and use as data or code (with caution!) as appropriate.

Note: Some versions (e.g. TC3 version) support a /F parameter:
"/F selects 'far' version (please read the documentation before using /F)."

Amusingly as I just discovered if you look up BGIOBJ in a physical Turbo C manual, it just refers to UTIL.DOC which can normally be found in C:\TC\DOC - having just re-referenced it for you I was reminded that it only talks about BGI files which we don't care about (certainly I never have). However don't be fooled you can use the utility for other purposes. Anyway, I have just noted UTIL.DOC basically explains that /F instructs BGIOBJ to use a different segment name other than _TEXT in the form of filename_TEXT - the UTIL.DOC documentation takes up a lot of space to explain this though :)


Some Borland compiler examples
Ok, firstly lets imagine we have a text file called HW.TXT which you've guessed it contains:

Hello World!

as above we use bgiobj or binobj to convert it (the parameters are the same):

bgiobj hw.txt hw hw
or
binobj hw.txt hw hw

The above will result in hw.obj - below are some examples of Borland linking:


Borland/Turbo C linking examples
With Borland C products linking an obj file in is very straight forward, e.g:

\tc\bin\bcc myproject.c hw.obj
or
\tc\bin\tcc myproject.c hw.obj

Note: Borland store BGIOBJ by default under C:\TC\BGI directory not C:\TC\BIN


Turbo Pascal example 1/2
Linking in OBJ data at compile with Turbo Pascal is however a bit more complex but can still be done. Firstly here is a basic example of how to fool TP's linker into letting us get away with including non-code object data:
{$F+}  {force far calls}

{$L hw.obj}

procedure hw; external;  {fool TP as $L is supposed to be for code only}

Begin
  Halt; {Halt as we do NOT want to run the following reference which is DATA}
  HW;   {We need to include a reference to it otherwise TP won't include it}
End.

Turbo Pascal example 2
In this example we print out the text that was linked into our EXE from HW.OBJ after fooling TP's linker as already shown above. Note: this time however we use a move to overcome Borland's checking for "invalid variables".

{$F+}  {force far calls}

{$L hw.obj}

procedure hw; external;  {fool TP as $L is supposed to be for code only}

Var
  MyMessage:array[1..12] of char; {Our example text is 12 bytes long}

Begin
  Writeln;
  Move(Mem[Seg(HW):Ofs(HW)], MyMessage, SizeOf(MyMessage)); {What invalid variable? :}
  Writeln('My Message = ', MyMessage);
  Halt; {Halt as we do NOT want to run the following reference which is DATA}
  HW;   {We need to include a reference otherwise TP won't include it}
End.


Note: There are many ways of doing things like the above to add data/code during (or after) linking with Borland's products. e.g. After linking you can use Ben Castricum's UNP (e.g. unp412.zip) has the "m" (MarkEXE) option to "insert a file into an EXE's header" which is another basic way of getting resources into EXE files.

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