fpm should detect operating system

[certik]

Given the issues in #141 to determine the OS type, I think the most robust is to do it like CMake: fpm will detect / know the operating system that it is on, and it will pass this information down the source files, for example in terms of macro definitions, such as:

• FPM_OS_LINUX
• FPM_OS_MACOS
• FPM_OS_WINDOWS

Or something like that. We might be even more specific than that if needed. This seems to be the most robust and cross-platform way to do it that will work with all Fortran compilers.

[certik]

I tried various ways using macros in #142, and none of them seem to work with gfortran. So that's why I think having fpm define those macros is the way to go.

[milancurcic]

Right, so if fpm itself can detect the operating system, what do you need the macros for? I thought the macros are only useful when your software doesn't have the information you need. Or am I missing something?

[certik]

It's a chicken and an egg. The fpm implementation in Fortran needs to know the system type so that we know what command to use to get the directory content. The most robust seems to be if the build system (whether cmake or fpm) passes this information in as macro definitions.

[milancurcic]

Okay, so the bootstrap Haskell fpm will know the OS and pass the macros down to Fortran fpm. Then in the future when you want to bootstrap Fortran fpm using Fortran fpm, then the OS information will already be available in the boostrap Fortran fpm binary. It made me dizzy for a little bit, but I think it works.

[certik]

Right. The other way to bootstrap fpm down the road will be via cmake (#123), so the cmake build system that fpm will generate will have to detect the OS type (which cmake knows how to do) and then create the proper FPM_OS_* macro defines.

[arjenmarkus]

You could use the commands that come with the operating system (for instance this website gives some indicators.
While this will not be waterproof, the module may simply test the various commands - whichever succeeds is the one we want.
I can give this a try.

[arjenmarkus]

I just tried:
ver in a Windows command box gives the indication of the Windows version
This does not work with MinGW or Cygwin, even though they are Windows-based OSes.
uname -a succeeds on MinGW, Cygwin and Linux with proper indications of all OS types.
I have no access to MacOS but I imagine that uname -a work fine there as well.
(Something to check: whether ver is not a haphazard program - for uname I guess /usr/bin/uname is restrictive enough?)

[certik]

Here is how we currently do this using environment variables:

fpm/fpm/src/fpm.f90

Line 16 in 6ef2546

integer function get_os_type() result(r)

[arjenmarkus]

Hm, the environment variable HOMEPATH is set to "\Users\markus" on my Cygwin and MinGW/w-64 installations. So, with the current procedure that would boil down to "Windows".

[milancurcic]

It looks like we may have to combine the current HOMEPATH query with a ver test suggested by @arjenmarkus if we want to differentiate MinGW or Cygwin from Windows.

[arjenmarkus]

Since they represent very different operating environments, I think we cannot ignore the difference ;). For instance: "dir" does not work under Cygwin or MinGW. Regards, Arjen Op do 23 jul. 2020 om 19:20 schreef Milan Curcic <notifications@github.com>:

…

It looks like we may have to combine the current HOMEPATH query with a ver test suggested by @arjenmarkus <https://github.com/arjenmarkus> if we want to differentiate MinGW or Cygwin from Windows. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#144 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAN6YR2ZDUGZDNVZCMXWNUDR5BWMXANCNFSM4PEZSOMQ> .

[arjenmarkus]

Oops, I was too hasty: "dir" does actually work and "dir -b" also. But then "dir /b" does not and, vice versa, under a Windows command box "dir -b" does not work - it looks for a file "-b". Regards, Arjen Op do 23 jul. 2020 om 19:22 schreef Arjen Markus <arjen.markus895@gmail.com

…

: Since they represent very different operating environments, I think we cannot ignore the difference ;). For instance: "dir" does not work under Cygwin or MinGW. Regards, Arjen Op do 23 jul. 2020 om 19:20 schreef Milan Curcic ***@***.*** >: > It looks like we may have to combine the current HOMEPATH query with a > ver test suggested by @arjenmarkus <https://github.com/arjenmarkus> if > we want to differentiate MinGW or Cygwin from Windows. > > — > You are receiving this because you were mentioned. > Reply to this email directly, view it on GitHub > <#144 (comment)>, > or unsubscribe > <https://github.com/notifications/unsubscribe-auth/AAN6YR2ZDUGZDNVZCMXWNUDR5BWMXANCNFSM4PEZSOMQ> > . >

[milancurcic]

Right, dir is part of GNU Coreutils, so it works on most Linux systems, but not on macOS for example. Best to stay away from it for making important decisions :).