Using config_setting and select for multiple combinations of parameters

[silves...@gmail.com]

Hi,

In my project I have multiple combinations of parameters that should result in the same select decision. However I have not been able to find a way to combine this. Is it somehow possible to either combine multiple config labels in one select option or to combine multiple combinations of command line parameters in config_setting?

An example:
config_setting(
name = "macos",
values = { "cpu": "darwin" },
)
config_setting(
name = "ios_arm",
values = { "cpu": "ios_arm64" },
)
config_setting(
name = "ios_x86",
values = { "cpu": "ios_x86_64" },
)
config_setting(
name = "linux",
values = { "cpu": "K8" },
)
config_setting(
name = "android",
values = < some android values >,
)

cc_library(
name = "MyLib",
srcs = select({
":macos": [ "darwin sources" ],
":ios_arm": [ "darwin sources" ],
":ios_x86": [ "darwin sources" ],
":linux": [ "linux sources" ],
":android": [ "android sources" ],
)

For the darwin sources there can be a lot of repetition (5 in my project). Similar for linux for both 32 and 64 bits, etc. The only way I currently know how to fix this is by using define_value and put these on the command-line.

Is there another way to combine this?

Kind regards,
Rob

[Austin Schuh]

We've been solving a slightly different problem, but I think the same idea applies.  We've been doing CPU and/or compiler selects, and have been putting the logic for those in a macro.  That has let us enforce that all the compilers we care about are handled, for example.

You could do a similar thing here by writing some sort of os_select macro that takes a map from OS to sources.  That would let you duplicate your labels inside the macro rather than out in the BUILD files.  It'll achieve the same effect, but will let you stop repeating yourself in BUILD files which is the important part.

Austin

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[silves...@gmail.com]

That indeed seems like an approach that works. I'll give it a try. Maybe I can even make a generic macro that takes a dict that allows a list of configs as keys and expands it as required for the select. Thank you for the inspiration!

Rob


Op dinsdag 10 oktober 2017 19:43:43 UTC+2 schreef Austin Schuh:

[Greg Estren]

Check out the Skylib selects._with_or macro, intended as a standardized version of exactly this:

https://github.com/bazelbuild/bazel-skylib/blob/ff23a62c57d2912c3073a69c12f42c3d6e58a957/lib/selects.bzl#L18