Is there a standard option of pass system environment option to SCons ENV?

[abitrolly]

#4239 proposes passing down reproducible builds var SOURCE_DATE_EPOCH automatically. I don't think it is a good way, but modifying SConstruct for passing it down explicitly, or making it optional, is also non-ideal. Is there a command line option for scons command that allows to pass systems environment variables to make them appear on SCons environment?

[bdbaddog]

This PR has been merged to enable such.. #4261

There is no SCons defined command line option to do such, but anyone creating a build system with SCons can easily add one.

SCons has an explicit guarantee to not do so by default.

[abitrolly]

If I understand it right, #4261 contains modification to make SCons pass SOURCE_DATE_EPOCH to all builds on specific machine automatically. This was discussed in #4239, and it's not what I've meant.

Is there an example how to add the env passthrough option to the SConstruct?

[acmorrow]

@abitrolly - If you arrange your SConstruct so it can take a "variables file" argument, you can write a variables file which forces the shell environment into the SCons ENV:

• https://github.com/mongodb/mongo/blob/fc98977e569884357584111e19873a0da6bf7217/SConstruct#L608-L613
• https://github.com/mongodb/mongo/blob/fc98977e569884357584111e19873a0da6bf7217/SConstruct#L916-L936
• https://github.com/mongodb/mongo/blob/fc98977e569884357584111e19873a0da6bf7217/SConstruct#L1071-L1076
• https://github.com/mongodb/mongo/blob/fc98977e569884357584111e19873a0da6bf7217/SConstruct#L1551
• https://github.com/mongodb/mongo/blob/fc98977e569884357584111e19873a0da6bf7217/etc/scons/propagate_shell_environment.vars

Now scons --variables-files=etc/scons/propagate_shell_environment.vars gets you the shell environment in ENV.

[abitrolly]

I mean the documentation about maing reproducible builds with SCons could include the example. When this thread will be indexed by search engines, example how to SOURCE_DATE_EPOCH down with the option will be useful.

[bdbaddog]

That's really beyond SCons' scope. See reproducible builds website for details on how to do so, then it's an implementation detail in any build system you use.

[abitrolly]

If dealing with SOURCE_DATE_EPOCH is beyond scope, then why #4261 got merged?

[mwichmann]

We can certainly add an example to the Cookbook (presented at https://scons-cookbook.readthedocs.io/en/latest/, repository at https://github.com/scons/cookbook). We used to put lots of stuff on the wiki, but once the wiki moved to github, that doesn't help because search engines don't get to index that.

[bdbaddog]

Still out of scope.

There is a FAQ item related to passing shell env vars into Environment()..
https://scons.org/faq.html#Why_doesn.27t_SCons_find_my_compiler.2BAC8-linker.2BAC8-etc..3F_I_can_execute_it_just_fine_from_the_command_line.