Select on host platform and execution platform

First of all, I apologize if I missed this info in the documentation.

I have a use case where I want my code-generator program to be compiled slightly differently for target platform, host platform, and execution platform by setting different defines.

This is a simplified example of what I’m trying to do. My target is aarch64, so that’s straight forward. My host and execution platforms are the same x86 machine but the CODEGEN_TARGET define value depends on whether it’s building for host or execution platform.

config_setting(
    name = "is_aarch64",
    constraint_values = [
        "@platforms//cpu:aarch64",
        "@platforms//os:linux",
    ],
)

config_setting(
    name = "is_x86_host",
    constraint_values = [ <---------------------------------+
        "@platforms//cpu:x86",                              |
        "@platforms//os:linux",                             |
        # How to define a host platform ?                   |
    ],                                                      +---- How to make the distinction between host platform and execution platform?
)                                                           |
                                                            |
config_setting(                                             |
    name = "is_x86_execution",                              |
    constraint_values = [ <---------------------------------+
        "@platforms//cpu:x86",
        "@platforms//os:linux",
        # How to define an execution platform ?
    ],
)

cc_library(
    name = "codeGen",
    hdrs = [
        "include/codeGen.h",
    ],
    defines = select({
        ":is_aarch64": ["CODEGEN_TARGET=aarch64"],
        ":is_x86_execution": ["CODEGEN_TARGET=aarch64"],  # <----------------- how do I write a rule that applies to execution platform only?
        ":is_x86_host": ["CODEGEN_TARGET=x86"],
    }),
    includes = ["include"],
    src = [
        "codeGen.cc",
    ],
)

I’m probably approaching it the wrong way. Any guidance would be appreciated.

[jasaw]

@sgowroji The question is how do I write a rule that applies to execution platform only, and another rule for host platform only? Just to clarify, bazel outputs the execution platform binaries to bazel-out/k8-opt-exec directory, whereas the host platform binaries go to bazel-out/host directory.

In my pseudo code above, in the cc_library section, I want the defines to select different C macro based on what platform (host or execution) it is compiling it for. The problem that I’m facing is, I can’t make the host/execution distinction in their respective config_setting.

[katre]

Closing this pending more information, feel free to re-open or re-file with more details.