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modes.rst

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Build modes

Contents

Overview

The Go toolchain can be configured to build targets in different modes using Bazel build settings specified on the command line or by using attributes specified on individual go_binary or go_test targets. For example, tests may be run in race mode with the command line flag --@io_bazel_rules_go//go/config:race or by setting race = "on" on the individual test targets.

Similarly, the Go toolchain can be made to cross-compile binaries for a specific platform by setting the --platforms command line flag or by setting the goos and goarch attributes of the binary target. For example, a binary could be built for linux / arm64 using the command line flag --platforms=@io_bazel_rules_go//go/toolchain:linux_arm64 or by setting goos = "linux" and goarch = "arm64".

Build settings

The build settings below are defined in the package @io_bazel_rules_go//go/config. They can all be set on the command line or using Bazel configuration transitions.

Name Type | Default value
static bool false
Statically links the target binary. May not always work since parts of the standard library and other C dependencies won't tolerate static linking. Works best with pure set as well.
race bool false
Instruments the binary for race detection. Programs will panic when a data race is detected. Requires cgo. Mutually exclusive with msan.
msan bool false
Instruments the binary for memory sanitization. Requires cgo. Mutually exclusive with race.
pure bool false
Disables cgo, even when a C/C++ toolchain is configured (similar to setting CGO_ENABLED=0). Packages that contain cgo code may still be built, but the cgo code will be filtered out, and the cgo build tag will be false.
debug bool false
Includes debugging information in compiled packages (using the -N and -l flags). This is always true with -c dbg.
gotags string_list []
Controls which build tags are enabled when evaluating build constraints in source files. Useful for conditional compilation.
linkmode string "normal"
Determines how the Go binary is built and linked. Similar to -buildmode. Must be one of "normal", "shared", "pie", "plugin", "c-shared", "c-archive".

Platforms

You can define a Bazel platform using the native platform rule. A platform is essentially a list of facts (constraint values) about a target platform. rules_go defines a platform for each configuration the Go toolchain supports in @io_bazel_rules_go//go/toolchain. There are also config_setting targets in @io_bazel_rules_go//go/platform that can be used to pick platform-specific sources or dependencies using select.

You can specify a target platform using the --platforms command line flag. Bazel will automatically select a registered toolchain compatible with the target platform (rules_go registers toolchains for all supported platforms). For example, you could build for Linux / arm64 with the flag --platforms=@io_bazel_rules_go//go/toolchain:linux_arm64.

You can set the goos and goarch attributes on an individual go_binary or go_test rule to build a binary for a specific platform. This sets the --platforms flag via Bazel configuration transitions.

Examples

Building pure go binaries

You can switch the default binaries to non cgo using

You can build pure go binaries by setting those attributes on a binary.

go_binary(
    name = "foo",
    srcs = ["foo.go"],
    pure = "on",
)

Building static binaries

Note that static linking does not work on darwin.

You can switch the default binaries to statically linked binaries using

You can build static go binaries by setting those attributes on a binary. If you want it to be fully static (no libc), you should also specify pure.

go_binary(
    name = "foo",
    srcs = ["foo.go"],
    static = "on",
)

Using the race detector

You can switch the default binaries to race detection mode, and thus also switch the mode of tests by using

bazel test --@io_bazel_rules_go//go/config:race //...

Alternatively, you can activate race detection for specific tests.

  go_test(
      name = "go_default_test",
      srcs = ["lib_test.go"],
      embed = [":go_default_library"],
      race = "on",
)