I skimmed the linked thread, but I don't really understand what the idea is here. It seems to have to do with FFLAGS specifically, but that's about all I can tell. Is this really a separate issue from gh-24974, and if so could this gain a self-contained problem statement and proposed solution?

I skimmed the linked thread, but I don't really understand what the idea is here. It seems to have to do with FFLAGS specifically, but that's about all I can tell. Is this really a separate issue from gh-24974, and if so could this gain a self-contained problem statement and proposed solution?

Sorry yeah this was not well phrased. The discussion on #24974 was about build systems. The last comment by @2sn as I understood it was related to a more fundamental problem, using environment variables in f2py code. This is part of the Fortran 2003 standard, GET_ENVIRONMENT_VARIABLE.

Though I'll close this since it is already supported 1.26.0:

! env_module.f90
MODULE env_module
  IMPLICIT NONE
CONTAINS
  SUBROUTINE get_env_value(varname, value)
    CHARACTER(LEN=*), INTENT(IN) :: varname
    CHARACTER(LEN=100), INTENT(OUT) :: value
    CHARACTER(LEN=100) :: buffer
    INTEGER :: status

    CALL GET_ENVIRONMENT_VARIABLE(varname, buffer, STATUS=status)

    IF (status == 0) THEN
      value = buffer
    ELSE
      value = 'NOT FOUND'
    END IF

  END SUBROUTINE get_env_value
END MODULE env_module

With f2py -c envlib.f90 -m envlib and:

In [1]: import envlib
   ...: import os
   ...: 
   ...: # Set an environment variable for testing
   ...: os.environ["TEST_VAR"] = "Hello, Fortran!"
   ...: 
   ...: # Retrieve the value using the Fortran subroutine
   ...: value = envlib.env_module.get_env_value("TEST_VAR")
   ...: print(f"Value of TEST_VAR: {value}")
   ...: 
   ...: value_not_found = envlib.env_module.get_env_value("NON_EXISTENT_VAR")
   ...: print(f"Value of NON_EXISTENT_VAR: {value_not_found}")
Value of TEST_VAR: b'Hello, Fortran!'
Value of NON_EXISTENT_VAR: b'NOT FOUND'

@2sn let me know if there was something else w.r.t. f2py and environment variables.

@HaoZeke
Your example seems to test exactly what I was after.
Thanks!

I may have been using some different compatibility library with F77 at the time I tested it, Ila few yea s Back, but that should not matter.