Wanting to understand Restunts source code structure

[llm]

Is it possible to "fix" these functions with your disassembled code. (I still have to process the rest of the code, maybe i can do that Wednesday or Friday). If both versions create a bit perfect assembly then they should be interchangeable right?

sadly not direct - the IDA Database (IDB) is not really good merge-able - doesn't cleany follow source-only principe (much more then every tool i know, but still not enough) - but i think i will be ok in the end

[llm]

Is this kind of optimization the reason that it is difficult to reverse assembly back to C? (after it is assembled, compiled, decompiled, disassembled and converted to C) I probably have the steps wrong or mixed but (again >) you know what I mean. 

thats the primary reason with todays compilers, they optimize it the code so damn hard that you even can't find the functions anymore (inlineing etc.) - old 1990 compilers lucky weren't that advanced
so at least for Stunts - every C function (that implise cdecl calling convention) is more or less directly "seeable" also the parameters etc. because there is nearly no optimization

the pure assembler based functions (written in assembler in original) like the 3d engine doesn't need to follow any calling convention and can transport function-parameters in any technical possible way - using registers, evil stack filling, etc. - this are harder to detect - because stack pushes are very easy to see, some registers sets somewhere before the call not that much - you need to read the function code to understand if a register is a parameter, for a cdecl function you just need to look for add sp,VALUE after a call and some pushes before and its absolutley clear (in the case of stunts) that it is a cdecl C function
so i thing every call ..., add sp,VALUE is a cdecl C function call in the code

[llm]

sorry

Code Select Expand

... For this reason the number of arguments is not appended to the name of the function by the compiler, and the assembler and the linker are therefore unable to determine if an incorrect number of arguments is used...
is that text from me? because that talks about name-mangling, that means the signature types of the function are also attached in a special way to the function name - but that does not happen for cdecl C functions - so its not relevant here

and this "problem" only happen with variadic parameters - that means functions like printf with an open parameter count - these variadic parameters
are nearly never used in normal code - so also not relevant here

[Daniel3D]

sorry

Code Select Expand

... For this reason the number of arguments is not appended to the name of the function by the compiler, and the assembler and the linker are therefore unable to determine if an incorrect number of arguments is used...
is that text from me? because that talks about name-mangling, that means the signature types of the function are also attached in a special way to the function name - but that does not happen for cdecl C functions - so its not relevant here

and this "problem" only happen with variadic parameters - that means functions like printf with an open parameter count - these variadic parameters
are nearly never used in normal code - so also not relevant here

No it is form the link you sent:

CDECL
In the CDECL calling convention the following holds:

Arguments are passed on the stack in Right-to-Left order, and return values are passed in eax.
The calling function cleans the stack. This allows CDECL functions to have variable-length argument lists (aka variadic functions). For this reason the number of arguments is not appended to the name of the function by the compiler, and the assembler and the linker are therefore unable to determine if an incorrect number of arguments is used.

[Daniel3D]

im currently a little bit confused about the current state of some functions in the asmorig - some of the functions you've showed me are full of unused labels, messing the asm code a little
these labels do not exists if i freshly analyze the current game exe with IDA - need to find out what these labels are for

The code has things that even i find strange, like in seg000:

Code Select Expand

loc_143BB:
    cmp     ax, 4D00h
    [u]jnz     short loc_143C3[/u]
    jmp     loc_144A4
loc_143C3:
    jmp     loc_14188
loc_143C6:
    cmp     [bp+var_selectedmenu], 0
    jnz     sh
I guess this could be written as:

Code Select Expand

loc_143BB:
    cmp     ax, 4D00h
    jnz     short loc_14188            ;loc_143C3
    jmp     loc_144A4
                                       ;loc_143C3:
                                       ;jmp     loc_14188
loc_143C6:
    cmp     [bp+var_selectedmenu], 0
    jnz     sh

[llm]

im currently a little bit confused about the current state of some functions in the asmorig - some of the functions you've showed me are full of unused labels, messing the asm code a little
these labels do not exists if i freshly analyze the current game exe with IDA - need to find out what these labels are for

The code has things that even i find strange, like in seg000:

Code Select Expand

loc_143BB:
    cmp     ax, 4D00h
    [u]jnz     short loc_143C3[/u]
    jmp     loc_144A4
loc_143C3:
    jmp     loc_14188
loc_143C6:
    cmp     [bp+var_selectedmenu], 0
    jnz     sh
I guess this could be written as:

Code Select Expand

loc_143BB:
    cmp     ax, 4D00h
    jnz     short loc_14188            ;loc_143C3
    jmp     loc_144A4
                                       ;loc_143C3:
                                       ;jmp     loc_14188
loc_143C6:
    cmp     [bp+var_selectedmenu], 0
    jnz     sh

you're right - could be written as you said

sometimes assembler is that much of code that minor details like these gets lost while
developing because it still works - seems to be assembler-code in the first place or
some strage C code with gotos in original - the C code of that 2000 lines monster would be somewhere around <200-300 lines i think

or in Kevin Pickell words:

It was my first 3d game and I made many mistakes

[Cas]

Take into account that conditional jumps are always short (maybe there are longer, but not in real mode, if I'm not mistaken). This means that you can't jump more than 128 bytes from a location with a conditional jump. This is why they're used for branching, but then inconditional jumps are used for moving between different regions of code. In some cases, if short enough, you can do this.

[llm]

Cas is correct, i've forgot that detail

so your logic is correct Daniel but the CPU still needs different code

[Daniel3D]

Cas is correct, i've forgot that detail

so your logic is correct Daniel but the CPU still needs different code

Nobody can know everything. But you two are such opposites in your experience that you have a very broad knowledge spectrum together.

[Cas]

The important thing is what we know, not what we like, so it's good to be able to complement

[llm]

im currently a little bit confused about the current state of some functions in the asmorig - some of the functions you've showed me are full of unused labels, messing the asm code a little
these labels do not exists if i freshly analyze the current game exe with IDA - need to find out what these labels are for

found the reason for that: IDA got a "Display assembly lines/basic block boundaries" feature for the disassembling - these strange lables get generated if that option is activated - sadly that feature can't be reverted

[Daniel3D]

im currently a little bit confused about the current state of some functions in the asmorig - some of the functions you've showed me are full of unused labels, messing the asm code a little
these labels do not exists if i freshly analyze the current game exe with IDA - need to find out what these labels are for

found the reason for that: IDA got a "Display assembly lines/basic block boundaries" feature for the disassembling - these strange lables get generated if that option is activated - sadly that feature can't be reverted

There are a lot of them (if i read correctly)
Is it possible to redo it while maintaining the labels and comments that are made?

[llm]

There are a lot of them (if i read correctly)
Is it possible to redo it while maintaining the labels and comments that are made?

sadly that feature can't be reverted

but i check if there is some other option to revert it