Suggestions on 'strict-ness' of FASM

Index > Compiler Internals > Suggestions on 'strict-ness' of FASM

Author

Thread

AsmGuru62

Joined: 28 Jan 2004
Posts: 1694
Location: Toronto, Canada

AsmGuru62 29 Dec 2011, 13:43

Hi everyone,

Lately I was writing a lot of code and I made some 'blunders'.
Now, that I thought about it -- FASM as a compiler could warn me of a code situations, which are probably incorrect.
I wonder if FASM has any warnings right now in its arsenal.
I know that HLLs have quite a bit of warnings -- protecting the programmer, so to speak.
Smile

So, I have two warning suggestions.

First is about the 'virtual' directive.
Say, I have the following statement:

Code:

virtual at 0
TApplication:
    .Field1  dd ?
       .Field2  rd 16
      .Field3  rw 32
      .size = $
end virtual

Now, somewhere in my code I want to point my register at TApplication.Field3:

Code:

mov ebx, [glb_pApp]             ; points to instance of TApplication
lea esi, [ebx + TApplication]   ; <-- Here I forgot the ".Field3"
;
; The above is incorrect!
; The below is what I needed.
;
lea       esi, [ebx + TApplication.Field3]

Now, the debugger shows that label from a virtual statement evaluates to 0 and that is fine, however it would have been nice if FASM can warn about a situation where the label is used without a field.
===

Second is about the anonymous label ("@@:" <-- this one!).
Usually, these labels are good in short distances. When the distance increases -- there is a possibility of a mistake to be made. The code usually contains procedures and it would be nice if FASM could warn if a target for anonymous JMP (@f,@r) is located in another procedure:

Code:

Procedure1:
  test    eax, eax
    jz      @f
  ...
@@:
      ...
 test    eax, eax
    jz      @f
  ...
 ...     ; <-- Somewhere here is forgotten '@@:'
    ret

Procedure2:
  mov     ecx, 256
@@:             ; <-- Code from Procedure1 will fall here!
       ...
 loop    @r
  ret

29 Dec 2011, 13:43

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20531
Location: In your JS exploiting you and your system

revolution 29 Dec 2011, 13:52

I have two simple solutions for your two problems:

1. Don't use virtual for structures. Use struc, that is what it is for.

2. Don't use @@ anywhere. It is just a lazy way to create a label and IMO should not be used.

HTH

29 Dec 2011, 13:52

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8367
Location: Kraków, Poland

Tomasz Grysztar 29 Dec 2011, 14:35

fasm doesn't have any warning system, its directives are quite low-level, a building blocks which can be used to do many different things. So if only assembling the given composition of those pieces is possible, it is correct -simple as that. Warnings may discourage use of fasm's features in a way that was not predicted earlier, thus I do not plan to have any in the fasm's core. However you can have warnings implemented in some high-level macros, like "struct", which would be designed to be used strictly for one purpose, so it would be good to discourage any non-standard usage in their case.

29 Dec 2011, 14:35

< Last Thread | Next Thread >

Forum Rules:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum