Introduce initial Bazel build #1705

armandomontanez · 2024-05-16T01:48:29Z

Introduces the beginnings of a Bazel build for the Raspberry Pi Pico. The vast majority of preexisting build system configuration options are missing, but the build produces working binaries when used from an external project.

Introduces the initial foundations of a Bazel build, including a toolchain, critical generated headers, platform patterns, and enough BUILD files to build boot_stage2.

Uses archive_override where applicable to allow transitive bzlmod deps to propagate.

Makes an objcopy alias that redirects to the objcopy tool for the current exec platform, which allows boot_stage2 to build on Linux, macOS, and Windows.

Adds initial set of generated Bazel build files. Note that these do not yet build, as dependency cycles are present.

Fixes many dependency cycles, some were unintentionally created by the build file generator, others are true dependency cycles that require manual workarounds.

Silences a stray warning in the Bazel build.

This makes `bazel build //...` succeed, and also prevents the fetching of toolchains that aren't compatible with the current execution environment (i.e. Windows computers will no longer try to download macOS toolchains).

Finishes out the remainder of the work required to successfully compile a working blinky example.

Fixes some dependencies around pico_stdlib so that pico_stdlib links properly and UART stdio works.

Adds external an external registry for resolving Bazel module dependencies.

Provides the appropriate defines for host builds to support the picotool build.

The -ffreestanding toolchain flag is quite strict, so remove it from the Bazel toolchain.

Cuts out most of the Bazel toolchain flags and only specifies the bare-minimum set of flags. Also, adds wrapper linker flags for functions the SDK wraps.

Adds initial TinyUSB support and enough integration to get USB serial working.

Removes comments that indicates BUILD.bazel files are generated. This was used during initial bringup to indicate hand-crafted vs automatically generated BUILD.bazel files.

Prevents USB libraries from being built unless the build is properly configured to use them.

Moves toolchain configuration to use the new rules in rules_cc.

MODULE.bazel

armandomontanez · 2024-05-16T01:59:12Z

@kilograham I've put together an initial PR for adding a Bazel build, I have a few minor bits of cleanup before this is fully ready to merge, but I wanted to raise it to you now so you can start sharing any feedback/questions/concerns you may have now. @tpudlik has offered to review this from the Bazel side of things.

Cleans up trailing whitespace and runs the black formatter on parse_version.py.

Consolidates the class/chip constraint settings to be a single constraint_setting with a config_setting that represents the rp2 class.

Includes a necessary fix for the target_compatible_with expression in the cc_toolchain to work as intended.

Moves toolchain definitions from pico.bzl to BUILD.bazel to make them easier to find and read.

Fix trivial formatting issues by running buildifier on all BUILD.bazel files.

Makes a simple objcopy rule to remove direct references to the ARM toolchains.

Critical flags were not being applied to link steps. This applies -mcpu and -mthumb to the link steps to make the produced binaries work again.

bazel/README.md

tpudlik · 2024-05-20T23:35:05Z

bazel/README.md

+build --@rules_cc//cc/toolchains:experimental_enable_rule_based_toolchains
+```
+
+### Ready to build!


Should the README mention pico_config_extra_headers and pico_config_platform_headers?

Added instructions for these. They'll get totally reworked shortly, but it's good to document what's there!

tpudlik · 2024-05-20T23:36:30Z

bazel/constraint/BUILD.bazel

@@ -0,0 +1,43 @@
+package(default_visibility = ["//visibility:public"])
+
+constraint_setting(


The constraint_settings should really have comments explaining what they mean!

Eventually, will each header in src/boards/include/boards have a corresponding sdk_target constraint_value?

No, I don't think we'll have a constraint for each board. I've added a comment to clarify. After this first PR is merged, I'll be focusing on doing a comprehensive pass over the SDK configuration and then provide better foundations for configuration options. I have some ideas here, but I'd rather build those out as a separate PR so we can review/discuss them in isolation.

tpudlik · 2024-05-21T20:32:01Z

bazel/parse_version.py

This worries me a little. It seems brittle and complex... Ideally the version information would be exposed in a file with a simpler syntax. And as an intermediate solution, maybe some duplication (a handwritten header that needs to match the CMake) would be better. https://xkcd.com/1171/

In the MODULE.bazel we'll need to explicitly list a version anyway. I've reworked this script to just use that version. It's way simpler now.

src/rp2_common/boot_stage2/BUILD.bazel

tpudlik · 2024-05-21T21:24:32Z

src/rp2_common/pico_async_context/BUILD.bazel

+        "include/pico/async_context_threadsafe_background.h",
+    ],
+    includes = ["include"],
+    # Missing deps for:


Will all of these come from FreeRTOS? Another reason to upstream our FreeRTOS build file (https://pwbug.dev/326625641)!

Yeah, these are all provided by FreeRTOS. Interestingly I'm not seeing CMake configuration options for turning this on/off despite it seeming to be an optional feature. I'll mark this on my TODO list.

tpudlik · 2024-05-21T21:26:11Z

src/rp2_common/pico_printf/BUILD.bazel

+    alwayslink = True,  # Ensures the wrapped symbols are linked in.
+)
+
+# TODO: Support printf_none.S.


Could you expand the TODO to mention why that's nontrivial?

Updated here and elsewhere. TL;DR: we need to set up configuration patterns since it's mutually exclusive.

* pico_bit_ops was incomplete. * pico_double and pico_float were trying to link in the "none" implementation.

Improves documentation and comments across the Bazel build.

Switches genrules to use skylib rules to simplify things. Reworks version header generation to use the Bazel module version rather than parsing CMake.

Moves `includes` to be enumerated on the correct library.

armandomontanez

Ready for another pass! :)

armandomontanez · 2024-05-22T20:12:07Z

bazel/constraint/BUILD.bazel

@@ -0,0 +1,43 @@
+package(default_visibility = ["//visibility:public"])
+
+constraint_setting(


No, I don't think we'll have a constraint for each board. I've added a comment to clarify. After this first PR is merged, I'll be focusing on doing a comprehensive pass over the SDK configuration and then provide better foundations for configuration options. I have some ideas here, but I'd rather build those out as a separate PR so we can review/discuss them in isolation.

armandomontanez · 2024-05-22T20:13:48Z

bazel/parse_version.py

In the MODULE.bazel we'll need to explicitly list a version anyway. I've reworked this script to just use that version. It's way simpler now.

armandomontanez · 2024-05-22T20:15:39Z

bazel/platform/BUILD.bazel

I'm trying to design everything so that the host works out-of-the-box without having to specify --platforms or --host_platform. I have a follow-up branch with work that gets the host working with just a bazel build //....

armandomontanez · 2024-05-22T20:17:03Z

bazel/platform/BUILD.bazel

+    name = "rp2040",
+    constraint_values = [
+        "@pico-sdk//bazel/constraint:rp2040",
+        "@platforms//cpu:armv6-m",  # This is just FYI.


This is a well-known constraint though. Since there's a correct value, I feel we should just configure it so people aren't left confused as to why it's unset.

armandomontanez · 2024-05-22T20:32:10Z

bazel/toolchain/BUILD.bazel

+    overrides = "@rules_cc//cc/toolchains/features:dbg",
+)
+
+# TODO: This is required for now, but hopefully will eventually go away.


Filed bazelbuild/rules_cc#224

src/rp2_common/boot_stage2/BUILD.bazel

armandomontanez · 2024-05-22T23:13:59Z

bazel/README.md

+build --@rules_cc//cc/toolchains:experimental_enable_rule_based_toolchains
+```
+
+### Ready to build!


Added instructions for these. They'll get totally reworked shortly, but it's good to document what's there!

bazel/parse_version.py

src/rp2_common/boot_stage2/BUILD.bazel

armandomontanez · 2024-05-22T23:31:40Z

src/rp2_common/pico_async_context/BUILD.bazel

+        "include/pico/async_context_threadsafe_background.h",
+    ],
+    includes = ["include"],
+    # Missing deps for:


Yeah, these are all provided by FreeRTOS. Interestingly I'm not seeing CMake configuration options for turning this on/off despite it seeming to be an optional feature. I'll mark this on my TODO list.

WORKSPACE Bazel projects don't support querying module version, so add a fallback of '0.0.1-WORKSPACE' so the build can succeed.

Prevents Bazel from ever trying to link malloc into the boot_stage2 binary.

A dedicated boot_stage2 platform introduces a lot of complexity that needs to be more thought-through.

kilograham

I trust that this has stabilized enough for a baseline build... since it is entirely orthogonal to the CMake build, it can evolve independently.

armandomontanez and others added 21 commits February 17, 2024 17:08

Build boot_stage2 with Bazel

915d92b

Introduces the initial foundations of a Bazel build, including a toolchain, critical generated headers, platform patterns, and enough BUILD files to build boot_stage2.

Bazel libraries to support picotool

60607f4

Move SDK defines to toolchain

4d6488a

Switch to archive_override in MODULE.bazel

64de6dc

Uses archive_override where applicable to allow transitive bzlmod deps to propagate.

Multiplatform objcopy selection in Bazel build

32d5aa6

Makes an objcopy alias that redirects to the objcopy tool for the current exec platform, which allows boot_stage2 to build on Linux, macOS, and Windows.

Generate Bazel build files

9bd1fc1

Adds initial set of generated Bazel build files. Note that these do not yet build, as dependency cycles are present.

Fix dependency cycles in Bazel build

19711c6

Fixes many dependency cycles, some were unintentionally created by the build file generator, others are true dependency cycles that require manual workarounds.

Silence warning in pico_stdio Bazel build

769d046

Silences a stray warning in the Bazel build.

Fix wildcard Bazel build

de9bccc

This makes `bazel build //...` succeed, and also prevents the fetching of toolchains that aren't compatible with the current execution environment (i.e. Windows computers will no longer try to download macOS toolchains).

Get the SDK working

980bcb0

Finishes out the remainder of the work required to successfully compile a working blinky example.

Fix UART stdio dependencies in Bazel build

9c4e8ea

Fixes some dependencies around pico_stdlib so that pico_stdlib links properly and UART stdio works.

Add linux support to Bazel build

07890a2

Get Bazel deps from registry

61674d0

Adds external an external registry for resolving Bazel module dependencies.

Fix host configuration for picotool

f5527c7

Provides the appropriate defines for host builds to support the picotool build.

Remove -ffreestanding from Bazel toolchain

6baffc8

The -ffreestanding toolchain flag is quite strict, so remove it from the Bazel toolchain.

Remove unused .bzl file

1a0030c

Reduce Bazel compiler flags

b462d49

Cuts out most of the Bazel toolchain flags and only specifies the bare-minimum set of flags. Also, adds wrapper linker flags for functions the SDK wraps.

Get USB serial working

b5c6e7b

Adds initial TinyUSB support and enough integration to get USB serial working.

Remove "Generated build file"

274a431

Removes comments that indicates BUILD.bazel files are generated. This was used during initial bringup to indicate hand-crafted vs automatically generated BUILD.bazel files.

Do not build USB libraries unless configured

5be54d8

Prevents USB libraries from being built unless the build is properly configured to use them.

Switch to rules_cc toolchains

8f7ba9e

Moves toolchain configuration to use the new rules in rules_cc.

armandomontanez commented May 16, 2024

View reviewed changes

MODULE.bazel Outdated Show resolved Hide resolved

armandomontanez added 7 commits May 16, 2024 09:02

Minor cleanup in parse_version.py

7ef45fa

Cleans up trailing whitespace and runs the black formatter on parse_version.py.

Simplify constraint dimensions in Bazel build

8ac471b

Consolidates the class/chip constraint settings to be a single constraint_setting with a config_setting that represents the rp2 class.

Update pin of rules_cc in Bazel build

a2206fa

Includes a necessary fix for the target_compatible_with expression in the cc_toolchain to work as intended.

Move toolchains from pico.bzl to BUILD.bazel

3deb0eb

Moves toolchain definitions from pico.bzl to BUILD.bazel to make them easier to find and read.

Run buildifier on Bazel build files

616a3f3

Fix trivial formatting issues by running buildifier on all BUILD.bazel files.

Make objcopy rule

22f48b1

Makes a simple objcopy rule to remove direct references to the ARM toolchains.

Fix link flags in Bazel build

ba3c006

Critical flags were not being applied to link steps. This applies -mcpu and -mthumb to the link steps to make the produced binaries work again.

armandomontanez force-pushed the initial-bazel-build branch from 986aa77 to ba3c006 Compare May 16, 2024 22:37

Mention missing host build support

84ed595

armandomontanez marked this pull request as ready for review May 16, 2024 23:05

kilograham added the build label May 19, 2024

kilograham added this to the 1.6.0 milestone May 19, 2024

kilograham added non-cmake orphan PR labels May 19, 2024

kilograham modified the milestones: 1.6.1, 1.6.0 May 19, 2024

tpudlik reviewed May 21, 2024

View reviewed changes

armandomontanez added 4 commits May 21, 2024 15:42

Fix various Bazel library rules

ce0430b

* pico_bit_ops was incomplete. * pico_double and pico_float were trying to link in the "none" implementation.

Extend Bazel build documentation

77c4ae0

Improves documentation and comments across the Bazel build.

Clean up auxilary tools in Bazel build

241b645

Switches genrules to use skylib rules to simplify things. Reworks version header generation to use the Bazel module version rather than parsing CMake.

Update boot_stage2 Bazel build file

7686ebb

Moves `includes` to be enumerated on the correct library.

armandomontanez commented May 22, 2024

View reviewed changes

armandomontanez requested a review from tpudlik May 22, 2024 23:40

armandomontanez added 5 commits May 24, 2024 08:53

Add WORKSPACE version fallback

7be6b5c

WORKSPACE Bazel projects don't support querying module version, so add a fallback of '0.0.1-WORKSPACE' so the build can succeed.

Fix malloc handling in Bazel build

f5f8ce7

Fix Bazel dependency cycle in pico_malloc

20e197a

Prevent malloc from being linked into boot_stage2

db8bbc5

Prevents Bazel from ever trying to link malloc into the boot_stage2 binary.

Remove custom bootloader platform

fb61760

A dedicated boot_stage2 platform introduces a lot of complexity that needs to be more thought-through.

kilograham requested review from kilograham and removed request for tpudlik June 4, 2024 23:48

kilograham approved these changes Jun 4, 2024

View reviewed changes

kilograham merged commit abce1d4 into raspberrypi:develop Jun 4, 2024
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Introduce initial Bazel build #1705

Introduce initial Bazel build #1705

armandomontanez commented May 16, 2024

armandomontanez commented May 16, 2024

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		@@ -0,0 +1,43 @@
		package(default_visibility = ["//visibility:public"])

		constraint_setting(

Introduce initial Bazel build #1705

Introduce initial Bazel build #1705

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