I reached a point at which I don't think I am exactly understanding how
the racket compilation pipeline works.

My software has several compile time options that use environment
variables to be read (since I can't think of another way to do it) so I
define a compile time variable as:

(define-for-syntax enable-contracts?
  (and (getenv "S10_ENABLE_CONTRACTS") #true))

And then I create a macro to move this compile-time variable to runtime:
(define-syntax (compiled-with-contracts? stx)
  (datum->syntax stx enable-contracts?))

I have a few of these so when I create a distribution, I first create an
executable with (I use create-embedding-executable but for simplicity,
lets say I am using raco):
S10_ENABLE_CONTRACTS=1 raco exe ...

I have a bunch of other options that don't matter for the moment.

One of the things I noticed is that in some cases when I run my
executable, compile time code living inside begin-for-syntax to check if
a variable has been defined during compilation or not is triggered. At a
point, which I didn't expect any more syntax expansion to occur.

I can't really reproduce the issue with a small example yet but I
noticed something:


#lang racket

(require (file "arch-choice.rkt"))

(module+ main
  (printf "arch: ~a~n" (get-path)))


#lang racket

(provide get-path)


  (define arch-path (getenv "ARCH"))

  (unless arch-path
    (raise-user-error 'driver "Please define ARCH with a suitable path")))

(define-syntax (get-path stx)
  (datum->syntax stx arch-path))

Then just to make sure nothing is compiled I remove my zos:
$ find . -type f -name '*.zo' -exec \{\} \;

Then compile it:
$ ARCH=foo raco exe main.rkt

In this case if you run ./main you'll get 'arch: foo' back which is fine
so I can't reproduce what I see in my software which is with some
combinations of compile time options, I see:
'driver: Please define ARCH environment variable'

which should even be part of the executable because it's a compile time
string (or so I thought).

So I did on the above example:
$ strings main | grep ARCH
''Please define ARCH with a suitable path

OK, so, this agrees with what I see in my program: compile-time error
strings still exist in the code. Why is that? I thought that only fully
expanded code (compiled-code) would make it to the executable file.

Another thing that might help me understand what's going on, is there a
way to extract the bytecode from the executable and decompile it?


Paulo Matos

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