Replace references of "host" with "exec". (#294)

This properly captures that we actually mean the exec platform in these
contexts. Also remove host_tools utils because we can not really do that
for the exec platform.

Author: siddharthab

Diff for: toolchain/cc_toolchain_config.bzl

@@ -19,7 +19,6 @@ load(
 load(
     "//toolchain/internal:common.bzl",
     _check_os_arch_keys = "check_os_arch_keys",
-    _host_tools = "host_tools",
     _os_arch_pair = "os_arch_pair",
 )
 
@@ -32,25 +31,23 @@ def _fmt_flags(flags, toolchain_path_prefix):
 # right paths and flags for the tools.
 def cc_toolchain_config(
         name,
-        host_arch,
-        host_os,
+        exec_arch,
+        exec_os,
         target_arch,
         target_os,
         target_system_name,
         toolchain_path_prefix,
         tools_path_prefix,
         wrapper_bin_prefix,
         compiler_configuration,
-        cxx_builtin_include_directories,
-        host_tools_info = {}):
-    host_os_arch_key = _os_arch_pair(host_os, host_arch)
+        cxx_builtin_include_directories):
+    exec_os_arch_key = _os_arch_pair(exec_os, exec_arch)
     target_os_arch_key = _os_arch_pair(target_os, target_arch)
-    _check_os_arch_keys([host_os_arch_key, target_os_arch_key])
+    _check_os_arch_keys([exec_os_arch_key, target_os_arch_key])
 
     # A bunch of variables that get passed straight through to
     # `create_cc_toolchain_config_info`.
     # TODO: What do these values mean, and are they actually all correct?
-    host_system_name = host_arch
     (
         toolchain_identifier,
         target_cpu,
@@ -107,7 +104,7 @@ def cc_toolchain_config(
         "-fdebug-prefix-map={}=__bazel_toolchain_llvm_repo__/".format(toolchain_path_prefix),
     ]
 
-    is_xcompile = not (host_os == target_os and host_arch == target_arch)
+    is_xcompile = not (exec_os == target_os and exec_arch == target_arch)
 
     # Default compiler flags:
     compile_flags = [
@@ -148,7 +145,7 @@ def cc_toolchain_config(
     archive_flags = []
 
     # Linker flags:
-    if host_os == "darwin" and not is_xcompile:
+    if exec_os == "darwin" and not is_xcompile:
         # lld is experimental for Mach-O, so we use the native ld64 linker.
         # TODO: How do we cross-compile from Linux to Darwin?
         use_lld = False
@@ -264,15 +261,18 @@ def cc_toolchain_config(
     ## NOTE: make variables are missing here; unix_cc_toolchain_config doesn't
     ## pass these to `create_cc_toolchain_config_info`.
 
-    # The tool names come from [here](https://github.com/bazelbuild/bazel/blob/c7e58e6ce0a78fdaff2d716b4864a5ace8917626/src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfiguration.java#L76-L90):
+    # The requirements here come from
+    # https://cs.opensource.google/bazel/bazel/+/master:src/main/starlark/builtins_bzl/common/cc/cc_toolchain_provider_helper.bzl;l=75;drc=f0150efd1cca473640269caaf92b5a23c288089d
+    # https://cs.opensource.google/bazel/bazel/+/master:src/main/java/com/google/devtools/build/lib/rules/cpp/CcModule.java;l=1257;drc=6743d76f9ecde726d592e88d8914b9db007b1c43
+    # https://cs.opensource.google/bazel/bazel/+/refs/tags/7.0.0:tools/cpp/unix_cc_toolchain_config.bzl;l=192,201;drc=044a14cca2747aeff258fc71eaeb153c08cb34d5
     # NOTE: Ensure these are listed in toolchain_tools in toolchain/internal/common.bzl.
     tool_paths = {
         "ar": tools_path_prefix + ("llvm-ar" if not use_libtool else "libtool"),
         "cpp": tools_path_prefix + "clang-cpp",
         "dwp": tools_path_prefix + "llvm-dwp",
         "gcc": wrapper_bin_prefix + "cc_wrapper.sh",
         "gcov": tools_path_prefix + "llvm-profdata",
-        "ld": tools_path_prefix + "ld.lld" if use_lld else _host_tools.get_and_assert(host_tools_info, "ld"),
+        "ld": tools_path_prefix + "ld.lld" if use_lld else "/usr/bin/ld",
         "llvm-cov": tools_path_prefix + "llvm-cov",
         "llvm-profdata": tools_path_prefix + "llvm-profdata",
         "nm": tools_path_prefix + "llvm-nm",
@@ -319,7 +319,7 @@ def cc_toolchain_config(
         cpu = target_cpu,
         compiler = compiler,
         toolchain_identifier = toolchain_identifier,
-        host_system_name = host_system_name,
+        host_system_name = exec_arch,
         target_system_name = target_system_name,
         target_libc = target_libc,
         abi_version = abi_version,

Diff for: toolchain/internal/common.bzl

@@ -15,6 +15,7 @@
 SUPPORTED_TARGETS = [("linux", "x86_64"), ("linux", "aarch64"), ("darwin", "x86_64"), ("darwin", "aarch64")]
 
 # Map of tool name to its symlinked name in the tools directory.
+# See tool_paths in toolchain/cc_toolchain_config.bzl.
 _toolchain_tools = {
     name: name
     for name in [
@@ -40,7 +41,7 @@ _toolchain_tools_darwin = {
     "llvm-libtool-darwin": "libtool",
 }
 
-def host_os_key(rctx):
+def exec_os_key(rctx):
     (os, version, arch) = os_version_arch(rctx)
     if version == "":
         return "%s-%s" % (os, arch)
@@ -154,14 +155,14 @@ def check_os_arch_keys(keys):
                 keys = ", ".join(_supported_os_arch),
             ))
 
-def host_os_arch_dict_value(rctx, attr_name, debug = False):
+def exec_os_arch_dict_value(rctx, attr_name, debug = False):
     # Gets a value from a dictionary keyed by host OS and arch.
     # Checks for the more specific key, then the less specific,
     # and finally the empty key as fallback.
     # Returns a tuple of the matching key and value.
 
     d = getattr(rctx.attr, attr_name)
-    key1 = host_os_key(rctx)
+    key1 = exec_os_key(rctx)
     if key1 in d:
         return (key1, d.get(key1))
 
@@ -230,32 +231,3 @@ def toolchain_tools(os):
     if os == "darwin":
         tools.update(_toolchain_tools_darwin)
     return tools
-
-def _get_host_tool_info(rctx, tool_path, tool_key = None):
-    if tool_key == None:
-        tool_key = tool_path
-
-    if tool_path == None or not rctx.path(tool_path).exists:
-        return {}
-
-    return {
-        tool_key: struct(
-            path = tool_path,
-            features = [],
-        ),
-    }
-
-def _extract_tool_path(tool_info):
-    # Have to support structs or dicts:
-    return tool_info.path if type(tool_info) == "struct" else tool_info["path"]
-
-def _get_host_tool(host_tool_info, tool_key):
-    if tool_key in host_tool_info:
-        return _extract_tool_path(host_tool_info[tool_key])
-    else:
-        return None
-
-host_tools = struct(
-    get_tool_info = _get_host_tool_info,
-    get_and_assert = _get_host_tool,
-)

Diff for: toolchain/internal/configure.bzl

@@ -22,8 +22,7 @@ load(
     _arch = "arch",
     _canonical_dir_path = "canonical_dir_path",
     _check_os_arch_keys = "check_os_arch_keys",
-    _host_os_arch_dict_value = "host_os_arch_dict_value",
-    _host_tools = "host_tools",
+    _exec_os_arch_dict_value = "exec_os_arch_dict_value",
     _is_absolute_path = "is_absolute_path",
     _list_to_string = "list_to_string",
     _os = "os",
@@ -63,11 +62,11 @@ def llvm_config_impl(rctx):
     if not rctx.attr.toolchain_roots:
         toolchain_root = ("@" if BZLMOD_ENABLED else "") + "@%s_llvm//" % rctx.attr.name
     else:
-        (_key, toolchain_root) = _host_os_arch_dict_value(rctx, "toolchain_roots")
+        (_key, toolchain_root) = _exec_os_arch_dict_value(rctx, "toolchain_roots")
 
     if not toolchain_root:
         fail("LLVM toolchain root missing for ({}, {})".format(os, arch))
-    (_key, llvm_version) = _host_os_arch_dict_value(rctx, "llvm_versions")
+    (_key, llvm_version) = _exec_os_arch_dict_value(rctx, "llvm_versions")
     if not llvm_version:
         # LLVM version missing for (os, arch)
         _empty_repository(rctx)
@@ -161,30 +160,20 @@ def llvm_config_impl(rctx):
         llvm_version = llvm_version,
         extra_compiler_files = rctx.attr.extra_compiler_files,
     )
-    host_dl_ext = "dylib" if os == "darwin" else "so"
-    host_tools_info = dict([
-        pair
-        for (key, tool_path) in [
-            # This is used when lld doesn't support the target platform (i.e.
-            # Mach-O for macOS):
-            ("ld", "/usr/bin/ld"),
-        ]
-        for pair in _host_tools.get_tool_info(rctx, tool_path, key).items()
-    ])
+    exec_dl_ext = "dylib" if os == "darwin" else "so"
     cc_toolchains_str, toolchain_labels_str = _cc_toolchains_str(
         rctx,
         workspace_name,
         toolchain_info,
         use_absolute_paths_llvm,
-        host_tools_info,
     )
 
     convenience_targets_str = _convenience_targets_str(
         rctx,
         use_absolute_paths_llvm,
         llvm_dist_rel_path,
         llvm_dist_label_prefix,
-        host_dl_ext,
+        exec_dl_ext,
     )
 
     # Convenience macro to register all generated toolchains.
@@ -226,8 +215,7 @@ def _cc_toolchains_str(
         rctx,
         workspace_name,
         toolchain_info,
-        use_absolute_paths_llvm,
-        host_tools_info):
+        use_absolute_paths_llvm):
     # Since all the toolchains rely on downloading the right LLVM toolchain for
     # the host architecture, we don't need to explicitly specify
     # `exec_compatible_with` attribute. If the host and execution platform are
@@ -252,7 +240,6 @@ def _cc_toolchains_str(
             target_arch,
             toolchain_info,
             use_absolute_paths_llvm,
-            host_tools_info,
         )
         if cc_toolchain_str:
             cc_toolchains_str = cc_toolchains_str + cc_toolchain_str
@@ -275,12 +262,11 @@ def _cc_toolchain_str(
         target_os,
         target_arch,
         toolchain_info,
-        use_absolute_paths_llvm,
-        host_tools_info):
-    host_os = toolchain_info.os
-    host_arch = toolchain_info.arch
+        use_absolute_paths_llvm):
+    exec_os = toolchain_info.os
+    exec_arch = toolchain_info.arch
 
-    host_os_bzl = _os_bzl(host_os)
+    exec_os_bzl = _os_bzl(exec_os)
     target_os_bzl = _os_bzl(target_os)
 
     target_pair = _os_arch_pair(target_os, target_arch)
@@ -293,20 +279,16 @@ def _cc_toolchain_str(
         sysroot_label_str = ""
 
     if not sysroot_path:
-        if host_os == target_os and host_arch == target_arch:
+        if exec_os == target_os and exec_arch == target_arch:
             # For darwin -> darwin, we can use the macOS SDK path.
-            sysroot_path = _default_sysroot_path(rctx, host_os)
+            sysroot_path = _default_sysroot_path(rctx, exec_os)
         else:
             # We are trying to cross-compile without a sysroot, let's bail.
             # TODO: Are there situations where we can continue?
             return ""
 
     extra_files_str = "\":internal-use-files\""
 
-    # `struct` isn't allowed in `BUILD` files so we JSON encode + decode to turn
-    # them into `dict`s.
-    host_tools_info = json.decode(json.encode(host_tools_info))
-
     # C++ built-in include directories.
     # This contains both the includes shipped with the compiler as well as the sysroot (or host)
     # include directories. While Bazel's default undeclared inclusions check does not seem to be
@@ -358,8 +340,8 @@ def _cc_toolchain_str(
 
 cc_toolchain_config(
     name = "local-{suffix}",
-    host_arch = "{host_arch}",
-    host_os = "{host_os}",
+    exec_arch = "{exec_arch}",
+    exec_os = "{exec_os}",
     target_arch = "{target_arch}",
     target_os = "{target_os}",
     target_system_name = "{target_system_name}",
@@ -382,15 +364,14 @@ cc_toolchain_config(
       "coverage_link_flags": {coverage_link_flags},
       "unfiltered_compile_flags": {unfiltered_compile_flags},
     }},
-    host_tools_info = {host_tools_info},
     cxx_builtin_include_directories = {cxx_builtin_include_directories},
 )
 
 toolchain(
     name = "cc-toolchain-{suffix}",
     exec_compatible_with = [
-        "@platforms//cpu:{host_arch}",
-        "@platforms//os:{host_os_bzl}",
+        "@platforms//cpu:{exec_arch}",
+        "@platforms//os:{exec_os_bzl}",
     ],
     target_compatible_with = [
         "@platforms//cpu:{target_arch}",
@@ -518,12 +499,12 @@ cc_toolchain(
         suffix = suffix,
         target_os = target_os,
         target_arch = target_arch,
-        host_os = host_os,
-        host_arch = host_arch,
+        exec_os = exec_os,
+        exec_arch = exec_arch,
         target_settings = _list_to_string(_dict_value(toolchain_info.target_settings_dict, target_pair)),
         target_os_bzl = target_os_bzl,
         target_system_name = target_system_name,
-        host_os_bzl = host_os_bzl,
+        exec_os_bzl = exec_os_bzl,
         llvm_dist_label_prefix = toolchain_info.llvm_dist_label_prefix,
         llvm_dist_path_prefix = toolchain_info.llvm_dist_path_prefix,
         tools_path_prefix = toolchain_info.tools_path_prefix,
@@ -544,7 +525,6 @@ cc_toolchain(
         coverage_link_flags = _list_to_string(_dict_value(toolchain_info.coverage_link_flags_dict, target_pair)),
         unfiltered_compile_flags = _list_to_string(_dict_value(toolchain_info.unfiltered_compile_flags_dict, target_pair)),
         extra_files_str = extra_files_str,
-        host_tools_info = host_tools_info,
         cxx_builtin_include_directories = _list_to_string([
             # Filter out non-existing directories with absolute paths as they
             # result in a -Wincomplete-umbrella warning when mentioned in the
@@ -556,12 +536,12 @@ cc_toolchain(
         extra_compiler_files = ("\"%s\"," % str(toolchain_info.extra_compiler_files)) if toolchain_info.extra_compiler_files else "",
     )
 
-def _convenience_targets_str(rctx, use_absolute_paths, llvm_dist_rel_path, llvm_dist_label_prefix, host_dl_ext):
+def _convenience_targets_str(rctx, use_absolute_paths, llvm_dist_rel_path, llvm_dist_label_prefix, exec_dl_ext):
     if use_absolute_paths:
         llvm_dist_label_prefix = ":"
         filenames = []
         for libname in _aliased_libs:
-            filename = "lib/{}.{}".format(libname, host_dl_ext)
+            filename = "lib/{}.{}".format(libname, exec_dl_ext)
             filenames.append(filename)
         for toolname in _aliased_tools:
             filename = "bin/{}".format(toolname)
@@ -575,7 +555,7 @@ def _convenience_targets_str(rctx, use_absolute_paths, llvm_dist_rel_path, llvm_
         template = """
 cc_import(
     name = "{name}",
-    shared_library = "{{llvm_dist_label_prefix}}lib/lib{name}.{{host_dl_ext}}",
+    shared_library = "{{llvm_dist_label_prefix}}lib/lib{name}.{{exec_dl_ext}}",
 )""".format(name = name)
         lib_target_strs.append(template)
 
@@ -591,7 +571,7 @@ native_binary(
 
     return "\n".join(lib_target_strs + tool_target_strs).format(
         llvm_dist_label_prefix = llvm_dist_label_prefix,
-        host_dl_ext = host_dl_ext,
+        exec_dl_ext = exec_dl_ext,
     )
 
 def _is_hermetic_or_exists(rctx, path, sysroot_prefix):

Diff for: toolchain/internal/llvm_distributions.bzl

@@ -13,7 +13,7 @@
 # limitations under the License.
 
 load("@bazel_tools//tools/build_defs/repo:utils.bzl", "read_netrc", "use_netrc")
-load("//toolchain/internal:common.bzl", _arch = "arch", _attr_dict = "attr_dict", _host_os_arch_dict_value = "host_os_arch_dict_value", _os = "os")
+load("//toolchain/internal:common.bzl", _arch = "arch", _attr_dict = "attr_dict", _exec_os_arch_dict_value = "exec_os_arch_dict_value", _os = "os")
 load("//toolchain/internal:release_name.bzl", _llvm_release_name = "llvm_release_name")
 
 # If a new LLVM version is missing from this list, please add the shasums here
@@ -547,7 +547,7 @@ def download_llvm(rctx):
     return updated_attrs
 
 def _urls(rctx):
-    (key, urls) = _host_os_arch_dict_value(rctx, "urls", debug = False)
+    (key, urls) = _exec_os_arch_dict_value(rctx, "urls", debug = False)
     if not urls:
         print("LLVM archive URLs missing and no default fallback provided; will try 'distribution' attribute")  # buildifier: disable=print
 
@@ -561,7 +561,7 @@ def _get_llvm_version(rctx):
         return rctx.attr.llvm_version
     if not rctx.attr.llvm_versions:
         fail("Neither 'llvm_version' nor 'llvm_versions' given.")
-    (_, llvm_version) = _host_os_arch_dict_value(rctx, "llvm_versions")
+    (_, llvm_version) = _exec_os_arch_dict_value(rctx, "llvm_versions")
     if not llvm_version:
         fail("LLVM version string missing for ({os}, {arch})", os = _os(rctx), arch = _arch(rctx))
     return llvm_version