Commit Graph

2 Commits

Author SHA1 Message Date
Kevin Lubick
7a14f783bd [bazel] Sketching out HelloWorld sk_app using GL
bazel run //example:hello_world --config=clang
causes a window to open and draws a circle and a square.
Text to follow in a future CL.

To make this work, I had to get rid of musl and use glibc.
All the shared libraries (.so files) that were pre-built
and available for download (e.g. from https://packages.debian.org/bullseye/amd64/libgl1/download)
were compiled against glibc. When I tried to run a
program statically linked with musl and dynamically linked
against things using glibc, I got a segmentation fault
on things like calloc().

Initial attempts to use glibc had failed because it was thought
that the libc.so.6 file could only be referred to by absolute
path (and thus Bazel would not be happy about it). As it turns out,
that was simply a misconfiguration of the builtin_sysroot
parameter to cc_common.create_cc_toolchain_config_info
(see //toolchain/clang_toolchain_config.bzl). By setting that
to `external/clang_linux_amd64` and not
`external/clang_linux_amd64/usr`, the libc binary which had
been extracted to `external/clang_linux_amd64/lib/x86_64-linux-gnu`
was perfectly reachable from
`external/clang_linux_amd64/usr/usr/lib/x86_64-linux-gnu/libc.so`

To bring in the shared libraries to link against (e.g. X11, GL)
I made build_toolchain.bzl easier to modify in that we simply need
to add a debian download url and sha256 hash to a list (rather than
having to plumb this through via arguments).

Recommended Review Order:
 - example/BUILD.bazel (not sure if we always want to set bare
   link arguments like that or if we want to use "features" to
   pass those along to the toolchain).
 - tools/sk_app/BUILD.bazel to see initial cc_library for
   wrapping sk_app code.
 - toolchain/build_toolchain.bzl to see removal of musl and
   new list of debs.
 - toolchain/clang_toolchain_config.bzl (where use of the
   no-canonical-prefixes was key to compilation success).
   Notice also that we statically linked libc++ (I did not
   have any shared libraries for it locally, so I guessed
   a typical developer might not either).
 - Rest of toolchain/ for trivial renames.
 - bazel/Makefile to see extra docs on those targets and
   a new target that compiles all the exes so far for a
   quick way to test the build.
 - third_party/BUILD.bazel and src/gpu/BUILD.bazel which have
   non-generated changes. (all other BUILD.bazel files do).
 - go.mod, which needed to update the infra repo version in
   order to pick up http://review.skia.org/491736).

Change-Id: I8687bd227353040eca2dffa9465798d8bd395027
Bug: skia:12541
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/492117
Reviewed-by: Ben Wagner <bungeman@google.com>
Reviewed-by: Leandro Lovisolo <lovisolo@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
2022-01-11 13:06:19 +00:00
Kevin Lubick
6ba9f702ba [bazel] Try adding cc_binary rules that use generated rules
To make the atomic rules a bit easier to work with, in many
of the folders, this adds in cc_library rules to group
together the sources from that folder (and subfolders
where prudent). We only needs sources because those atoms
should have their headers as deps.

One issue that was pointed out is that there is currently
no way to restrict the inclusion of certain packages,
a la, `gn check`. For example, there is no mechanism from
stopping a dev from adding
#include "modules/canvaskit/WasmCommon.h"
to something in //src/core (except circular dependencies).
We can probably address that using Bazel's visibility
rules as needed:
https://docs.bazel.build/versions/main/visibility.html
https://docs.bazel.build/versions/main/be/functions.html#package_group

It is recommended to look at this CL patchset by patchset.
PS1: Update gazelle command to generate rules in more folders.
PS2: A few changes to make generation work better.
PS3: The result of running make generate in //bazel
PS4: Adding the rules to build sksllex, the simplest binary I
     could find in the Skia repo.
PS5: Adding the rules to build skdiff, a more complex binary.
     I tried a few approaches, but ended up gravitating back
     towards the layout where we have each folder/package
     group up the sources. I imagine at some point, we'll have
     skdiff depend on skia_core or something, which will
     have things like //src/core, //src/codecs, //src/pathops
     all bundled together.
PS7: Added in the groupings of sources, similar to what we had
     earlier. I liked these for readability. These helped fix
     up the //:skia_core build, and by extension, the CanvasKit
     build.

Change-Id: I3faa7c4e821c876b243617aacf0246efa524cbde
Bug: skia:12541
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/476219
Reviewed-by: Ben Wagner <bungeman@google.com>
Reviewed-by: Leandro Lovisolo <lovisolo@google.com>
2021-11-30 18:18:53 +00:00