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toolchain.bzl
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toolchain.bzl
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"""Rules for defining toolchains"""
load(
":private/actions/compile.bzl",
"compile_binary",
"compile_library",
)
load(
":private/actions/link.bzl",
"link_binary",
"link_library_dynamic",
"link_library_static",
)
load(":private/actions/package.bzl", "package")
load(":private/set.bzl", "set")
load("@bazel_skylib//:lib.bzl", "paths")
_GHC_BINARIES = ["ghc", "ghc-pkg", "hsc2hs", "haddock", "ghci"]
def _run_ghc(hs, inputs, outputs, mnemonic, arguments, params_file = None, env = None, progress_message = None):
if not env:
env = hs.env
args = hs.actions.args()
args.add([hs.tools.ghc])
args.add([
# GHC uses C compiler for assemly, linking and preprocessing as well.
"-pgma",
hs.tools.cc.path,
"-pgmc",
hs.tools.cc.path,
"-pgml",
hs.tools.cc.path,
"-pgmP",
hs.tools.cc.path,
# Setting -pgm* flags explicitly has the unfortunate side effect
# of resetting any program flags in the GHC settings file. So we
# restore them here. See
# https://ghc.haskell.org/trac/ghc/ticket/7929.
"-optc-fno-stack-protector",
"-optP-E",
"-optP-undef",
"-optP-traditional",
])
extra_inputs = [hs.tools.ghc, hs.tools.cc]
if params_file:
command = '${1+"$@"} $(< %s)' % params_file.path
extra_inputs.append(params_file)
else:
command = '${1+"$@"}'
if type(inputs) == type(depset()):
inputs = depset(extra_inputs, transitive = [inputs])
else:
inputs += extra_inputs
hs.actions.run_shell(
inputs = inputs,
outputs = outputs,
command = command,
mnemonic = mnemonic,
progress_message = progress_message,
env = env,
arguments = [args] + arguments,
)
return args
def _haskell_toolchain_impl(ctx):
# Check that we have all that we want.
for tool in _GHC_BINARIES:
if tool not in [t.basename for t in ctx.files.tools]:
fail("Cannot find {} in {}".format(tool, ctx.attr.tools.label))
# Store the binaries of interest in ghc_binaries.
ghc_binaries = {}
for tool in ctx.files.tools:
if tool.basename in _GHC_BINARIES:
ghc_binaries[tool.basename] = tool.path
# Run a version check on the compiler.
for t in ctx.files.tools:
if t.basename == "ghc":
compiler = t
version_file = ctx.actions.declare_file("ghc-version")
ctx.actions.run_shell(
inputs = [compiler],
outputs = [version_file],
mnemonic = "HaskellVersionCheck",
command = """
{compiler} --numeric-version > {version_file}
if [[ {expected_version} != $(< {version_file}) ]]
then
echo GHC version $(< {version_file}) does not match expected version {expected_version}.
exit 1
fi
""".format(
compiler = compiler.path,
version_file = version_file.path,
expected_version = ctx.attr.version,
),
)
# NOTE The only way to let various executables know where other
# executables are located is often only via the PATH environment variable.
# For example, ghc uses gcc which is found on PATH. This forces us provide
# correct PATH value (with e.g. gcc on it) when we call executables such
# as ghc. However, this hurts hermeticity because if we construct PATH
# naively, i.e. through concatenation of directory names of all
# executables of interest, we also make other neighboring executables
# visible, and they indeed can influence the building process, which is
# undesirable.
#
# To prevent this, we create a special directory populated with symbolic
# links to all executables we want to make visible, and only to them. Then
# we make all rules depend on some of these symlinks, and provide PATH
# (always the same) that points only to this prepared directory with
# symlinks. This helps hermeticity and forces us to be explicit about all
# programs we need/use for building. Setting PATH and listing as inputs
# are both necessary for a tool to be available with this approach.
visible_binaries = "visible-binaries"
symlinks = set.empty()
inputs = []
inputs.extend(ctx.files.tools)
inputs.extend(ctx.files._crosstool)
targets_r = {}
targets_r.update({
"ar": ctx.host_fragments.cpp.ar_executable,
"cc": ctx.host_fragments.cpp.compiler_executable,
"ld": ctx.host_fragments.cpp.ld_executable,
"nm": ctx.host_fragments.cpp.nm_executable,
"cpp": ctx.host_fragments.cpp.preprocessor_executable,
"strip": ctx.host_fragments.cpp.strip_executable,
})
targets_r.update(ghc_binaries)
# If running on darwin but XCode is not installed (i.e., only the Command
# Line Tools are available), then Bazel will make ar_executable point to
# "/usr/bin/libtool". Since we call ar directly, override it.
# TODO: remove this if Bazel fixes its behavior.
# Upstream ticket: https://github.com/bazelbuild/bazel/issues/5127.
if targets_r["ar"].find("libtool") >= 0:
targets_r["ar"] = "/usr/bin/ar"
ar_runfiles = []
# "xcrunwrapper.sh" is a Bazel-generated dependency of the `ar` program on macOS.
xcrun_candidates = [f for f in ctx.files._crosstool if paths.basename(f.path) == "xcrunwrapper.sh"]
if xcrun_candidates:
xcrun = xcrun_candidates[0]
ar_runfiles += [xcrun]
targets_r["xcrunwrapper.sh"] = xcrun.path
if ctx.attr.c2hs != None:
targets_r["c2hs"] = ctx.file.c2hs.path
inputs.append(ctx.file.c2hs)
extra_binaries_names = set.empty()
for binary in ctx.files.extra_binaries:
targets_r[binary.basename] = binary.path
inputs.append(binary)
set.mutable_insert(extra_binaries_names, binary.basename)
extra_binaries_files = []
for target in targets_r:
symlink = ctx.actions.declare_file(
paths.join(visible_binaries, target),
)
symlink_target = targets_r[target]
if not paths.is_absolute(symlink_target):
symlink_target = paths.join("/".join([".."] * len(symlink.dirname.split("/"))), symlink_target)
ctx.actions.run(
inputs = inputs,
outputs = [symlink],
mnemonic = "Symlink",
executable = "ln",
# FIXME Currently this part of the process is not hermetic. This
# should be adjusted when
#
# https://github.com/bazelbuild/bazel/issues/4681
#
# is implemented.
use_default_shell_env = True,
arguments = [
"-s",
symlink_target,
symlink.path,
],
)
if target == "xcrunwrapper.sh":
ar_runfiles += [symlink]
if set.is_member(extra_binaries_names, target):
extra_binaries_files += [symlink]
set.mutable_insert(symlinks, symlink)
targets_w = [
"bash",
"cat",
"cp",
"grep",
"ln",
"mkdir",
"mktemp",
"rmdir",
]
for target in targets_w:
symlink = ctx.actions.declare_file(
paths.join(visible_binaries, paths.basename(target)),
)
ctx.actions.run_shell(
inputs = ctx.files.tools,
outputs = [symlink],
mnemonic = "Symlink",
command = """
mkdir -p $(dirname "{symlink}")
ln -s $(which "{target}") "{symlink}"
""".format(
target = target,
symlink = symlink.path,
),
use_default_shell_env = True,
)
set.mutable_insert(symlinks, symlink)
tools_struct_args = {
tool.basename.replace("-", "_"): tool
for tool in set.to_list(symlinks)
}
tools_runfiles_struct_args = {"ar": ar_runfiles}
locale_archive = None
if ctx.attr.locale_archive != None:
locale_archive = ctx.file.locale_archive
return [
platform_common.ToolchainInfo(
name = ctx.label.name,
tools = struct(**tools_struct_args),
tools_runfiles = struct(**tools_runfiles_struct_args),
extra_binaries = extra_binaries_files,
compiler_flags = ctx.attr.compiler_flags,
repl_ghci_args = ctx.attr.repl_ghci_args,
locale = ctx.attr.locale,
locale_archive = locale_archive,
mode = ctx.var["COMPILATION_MODE"],
actions = struct(
compile_binary = compile_binary,
compile_library = compile_library,
link_binary = link_binary,
link_library_dynamic = link_library_dynamic,
link_library_static = link_library_static,
package = package,
run_ghc = _run_ghc,
),
# All symlinks are guaranteed to be in the same directory so we just
# provide directory name of the first one (the collection cannot be
# empty). The rest of the program may rely consider visible_bin_path
# as the path to visible binaries, without recalculations.
visible_bin_path = set.to_list(symlinks)[0].dirname,
is_darwin = ctx.attr.is_darwin,
version = ctx.attr.version,
),
# Make everyone implicitly depend on the version_file, to force
# the version check.
DefaultInfo(files = depset([version_file])),
]
_haskell_toolchain = rule(
_haskell_toolchain_impl,
host_fragments = ["cpp"],
attrs = {
"tools": attr.label(
doc = "GHC and executables that come with it",
mandatory = True,
),
"compiler_flags": attr.string_list(
doc = "A collection of flags that will be passed to GHC on every invocation.",
),
"repl_ghci_args": attr.string_list(
doc = "A collection of flags that will be passed to GHCI on repl invocation. It extends the `compiler_flags` collection. Flags set here have precedance over `compiler_flags`.",
),
"c2hs": attr.label(
doc = "c2hs executable",
allow_single_file = True,
),
"version": attr.string(mandatory = True),
"is_darwin": attr.bool(mandatory = True),
"_crosstool": attr.label(
default = Label("//tools/defaults:crosstool"),
),
"extra_binaries": attr.label_list(
doc = "Additional binaries necessary for building",
default = [],
),
"locale": attr.string(
default = "en_US.UTF-8",
doc = "Locale that will be set during compiler invocations.",
),
"locale_archive": attr.label(
allow_single_file = True,
doc = """
Label pointing to the locale archive file to use. Mostly useful on NixOS.
""",
),
},
)
def haskell_toolchain(
name,
version,
tools,
compiler_flags = [],
repl_ghci_args = [],
**kwargs):
"""Declare a compiler toolchain.
You need at least one of these declared somewhere in your `BUILD` files
for the other rules to work. Once declared, you then need to *register*
the toolchain using `register_toolchain` in your `WORKSPACE` file (see
example below).
Example:
In a `BUILD` file:
```bzl
haskell_toolchain(
name = "ghc",
version = '1.2.3'
tools = ["@sys_ghc//:bin"],
compiler_flags = ["-Wall"],
c2hs = "@c2hs//:bin", # optional
)
```
where `@ghc` is an external repository defined in the `WORKSPACE`,
e.g. using:
```bzl
nixpkgs_package(
name = 'sys_ghc',
attribute_path = 'haskell.compiler.ghc822'
)
register_toolchain("//:ghc")
```
and for `@c2hs`:
```bzl
nixpkgs_package(
name = "c2hs",
attribute_path = "haskell.packages.ghc822.c2hs",
)
```
"""
impl_name = name + "-impl"
_haskell_toolchain(
name = impl_name,
version = version,
tools = tools,
compiler_flags = compiler_flags,
repl_ghci_args = repl_ghci_args,
visibility = ["//visibility:public"],
is_darwin = select({
"@bazel_tools//src/conditions:darwin": True,
"//conditions:default": False,
}),
**kwargs
)
native.toolchain(
name = name,
toolchain_type = "@io_tweag_rules_haskell//haskell:toolchain",
toolchain = ":" + impl_name,
exec_compatible_with = [
"@bazel_tools//platforms:x86_64",
],
target_compatible_with = [
"@bazel_tools//platforms:x86_64",
],
)