[fasmg] Can I Make a Custom Macro for the label: syntax?

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zicklag

Joined: 10 May 2025
Posts: 3

zicklag 10 May 2025, 02:12

I'm trying to create a custom label macro that will output all of the label names and their memory positions out to a separate file to use as a source map in an NES emulator.

It seems that there's a way to do that easy enough if I make a `label` macro and use the `label name` syntax, but I would like to continue being able to use the normal `label:` syntax.

Is there any way to do that?

10 May 2025, 02:12

zicklag

Joined: 10 May 2025
Posts: 3

zicklag 10 May 2025, 02:26

Oh, actually I just realized that it's pretty easy to use an unconditional macroinstruction to intercept all of the labels with a custom macro, but unfortunately I'm not seeing a way to generate the source map as a separate file.

As far as I can see fasmg only supports writing output to its main output file.

Code:

macro ?! line&
  match label_name:,line
    ; do custom stuff
    label label_name 
  else
    line
  end match
end macro

[/quote]

10 May 2025, 02:26

dosmancer

Joined: 20 Feb 2025
Posts: 17
Location: Kingdom of Sweden

dosmancer 10 May 2025, 03:29

zicklag wrote:

Oh, actually I just realized that it's pretty easy to use an unconditional macroinstruction to intercept all of the labels with a custom macro, but unfortunately I'm not seeing a way to generate the source map as a separate file.

As far as I can see fasmg only supports writing output to its main output file.
Code:
macro ?! line&
  match label_name:,line
    ; do custom stuff
    label label_name 
  else
    line
  end match
end macro
    

I slightly more lightway approach than a "catch-all" macro is a "catch-all" struc

See chapter 9 in https://flatassembler.net/docs.php?article=fasmg_manual#9

Code:

struc (label) ? line&
        . line
        ; need to collect the label and address too somehow
end struc

To catch labels created with the `label` command you need to override the label command too:

Code:

macro label? line&
        label line
        ; need to collect the label and address too somehow
end macro

To output data to a separate other file you need to use `virtual`. See chapter 13 https://flatassembler.net/docs.php?article=fasmg_manual#13

So you need to collect label names together with the addresses and then output them in your desired format into the virtual output area with the store command.

10 May 2025, 03:29

zicklag

Joined: 10 May 2025
Posts: 3

zicklag 10 May 2025, 16:07

Ah, the virtual blocks are exactly what I needed, thanks!

And now I understand labeled macroinstructions with the `struc` syntax.

After some reading and experimenting I was able to get fasmg to output an MLB file so that I can get the labels imported to the Mesen NES emulator debugger!

Thanks for the help!

I'm having fun trying to get started writing an NES game with fasmg. So cool to be able to customize the assembler for a new platform like this.

10 May 2025, 16:07

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