3 # Copyright 2021 The Chromium Authors
4 # Use of this source code is governed by a BSD-style license that can be
5 # found in the LICENSE file.
14 # Set up path to be able to import action_helpers.
16 os.path.join(os.path.dirname(os.path.abspath(__file__)), os.pardir,
20 # This script wraps rustc for (currently) these reasons:
21 # * To work around some ldflags escaping performed by ninja/gn
22 # * To remove dependencies on some environment variables from the .d file.
23 # * To enable use of .rsp files.
24 # * To work around two gn bugs on Windows
28 # This script performs a simple function to work around some of the
29 # parameter escaping performed by ninja/gn.
31 # rustc invocations are given access to {{rustflags}} and {{ldflags}}.
32 # We want to pass {{ldflags}} into rustc, using -Clink-args="{{ldflags}}".
33 # Unfortunately, ninja assumes that each item in {{ldflags}} is an
34 # independent command-line argument and will have escaped them appropriately
35 # for use on a bare command line, instead of in a string.
37 # This script converts such {{ldflags}} into individual -Clink-arg=X
40 # RUSTENV dependency stripping
42 # When Rust code depends on an environment variable at build-time
43 # (using the env! macro), rustc spots that and adds it to the .d file.
44 # Ninja then parses that .d file and determines that the environment
45 # dependency means that the target always needs to be rebuilt.
47 # That's all correct, but _we_ know that some of these environment
48 # variables (typically, all of them) are set by .gn files which ninja
49 # tracks independently. So we remove them from the .d file.
53 # We want to put the ninja/gn variables {{rustdeps}} and {{externs}}
54 # in an RSP file. Unfortunately, they are space-separated variables
55 # but Rust requires a newline-separated input. This script duly makes
56 # the adjustment. This works around a gn issue:
57 # TODO(https://bugs.chromium.org/p/gn/issues/detail?id=249): fix this
59 # WORKAROUND WINDOWS BUGS:
61 # On Windows platforms, this temporarily works around some issues in gn.
62 # See comments inline, linking to the relevant gn fixes.
65 # rustc_wrapper.py --rustc <path to rustc> --depfile <path to .d file>
66 # -- <normal rustc args> LDFLAGS {{ldflags}} RUSTENV {{rustenv}}
67 # The LDFLAGS token is discarded, and everything after that is converted
68 # to being a series of -Clink-arg=X arguments, until or unless RUSTENV
69 # is encountered, after which those are interpreted as environment
70 # variables to pass to rustc (and which will be removed from the .d file).
72 # Both LDFLAGS and RUSTENV **MUST** be specified, in that order, even if
73 # the list following them is empty.
75 # TODO(https://github.com/rust-lang/rust/issues/73632): avoid using rustc
76 # for linking in the first place. Most of our binaries are linked using
77 # clang directly, but there are some types of Rust build product which
78 # must currently be created by rustc (e.g. unit test executables). As
79 # part of support for using non-rustc linkers, we should arrange to extract
80 # such functionality from rustc so that we can make all types of binary
81 # using our clang toolchain. That will remove the need for most of this
84 FILE_RE = re.compile("[^:]+: (.+)")
87 # Equivalent of python3.9 built-in
88 def remove_lib_suffix_from_l_args(text):
89 if text.startswith("-l") and text.endswith(".lib"):
90 return text[:-len(".lib")]
94 def verify_inputs(depline, sources, abs_build_root):
95 """Verify everything used by rustc (found in `depline`) was specified in the
96 GN build rule (found in `sources` or `inputs`).
98 TODO(danakj): This allows things in `sources` that were not actually used by
99 rustc since third-party packages sources need to be a union of all build
100 configs/platforms for simplicity in generating build rules. For first-party
101 code we could be more strict and reject things in `sources` that were not
105 # str.removeprefix() does not exist before python 3.9.
106 def remove_prefix(text, prefix):
107 if text.startswith(prefix):
108 return text[len(prefix):]
111 def normalize_path(p):
112 return os.path.relpath(os.path.normpath(remove_prefix(
113 p, abs_build_root))).replace('\\', '/')
115 # Collect the files that rustc says are needed.
117 m = FILE_RE.match(depline)
120 found_files = {normalize_path(f): f for f in files.split()}
121 # Get which ones are not listed in GN.
122 missing_files = found_files.keys() - sources
124 if not missing_files:
127 # The matching did a bunch of path manipulation to get paths relative to the
128 # build dir such that they would match GN. In errors, we will print out the
129 # exact path that rustc produces for easier debugging and writing of stdlib
131 for file_files_key in missing_files:
132 gn_type = "sources" if file_files_key.endswith(".rs") else "inputs"
133 print(f'ERROR: file not in GN {gn_type}: {found_files[file_files_key]}',
139 parser = argparse.ArgumentParser()
140 parser.add_argument('--rustc', required=True, type=pathlib.Path)
141 parser.add_argument('--depfile', required=True, type=pathlib.Path)
142 parser.add_argument('--rsp', type=pathlib.Path, required=True)
143 parser.add_argument('--target-windows', action='store_true')
144 parser.add_argument('args', metavar='ARG', nargs='+')
146 args = parser.parse_args()
148 remaining_args = args.args
150 ldflags_separator = remaining_args.index("LDFLAGS")
151 rustenv_separator = remaining_args.index("RUSTENV", ldflags_separator)
152 # Sometimes we duplicate the SOURCES list into the command line for debugging
153 # issues on the bots.
155 sources_separator = remaining_args.index("SOURCES", rustenv_separator)
157 sources_separator = None
158 rustc_args = remaining_args[:ldflags_separator]
159 ldflags = remaining_args[ldflags_separator + 1:rustenv_separator]
160 rustenv = remaining_args[rustenv_separator + 1:sources_separator]
162 abs_build_root = os.getcwd().replace('\\', '/') + '/'
163 is_windows = sys.platform == 'win32' or args.target_windows
165 rustc_args.extend(["-Clink-arg=%s" % arg for arg in ldflags])
167 with open(args.rsp) as rspfile:
168 rsp_args = [l.rstrip() for l in rspfile.read().split(' ') if l.rstrip()]
170 sources_separator = rsp_args.index("SOURCES")
171 sources = set(rsp_args[sources_separator + 1:])
172 rsp_args = rsp_args[:sources_separator]
175 # Work around for "-l<foo>.lib", where ".lib" suffix is undesirable.
176 # Full fix will come from https://gn-review.googlesource.com/c/gn/+/12480
177 rsp_args = [remove_lib_suffix_from_l_args(arg) for arg in rsp_args]
178 out_rsp = str(args.rsp) + ".rsp"
179 with open(out_rsp, 'w') as rspfile:
180 # rustc needs the rsp file to be separated by newlines. Note that GN
181 # generates the file separated by spaces:
182 # https://bugs.chromium.org/p/gn/issues/detail?id=249,
183 rspfile.write("\n".join(rsp_args))
184 rustc_args.append(f'@{out_rsp}')
186 env = os.environ.copy()
189 (k, v) = item.split("=", 1)
191 fixed_env_vars.append(k)
194 r = subprocess.run([args.rustc, *rustc_args], env=env, check=False)
197 if r.returncode != 0:
198 sys.exit(r.returncode)
200 final_depfile_lines = []
202 with open(args.depfile, encoding="utf-8") as d:
203 # Figure out which lines we want to keep in the depfile. If it's not the
204 # whole file, we will rewrite the file.
205 env_dep_re = re.compile("# env-dep:(.*)=.*")
207 m = env_dep_re.match(line)
208 if m and m.group(1) in fixed_env_vars:
209 dirty = True # We want to skip this line.
211 final_depfile_lines.append(line)
213 # Verify each dependent file is listed in sources/inputs.
214 for line in final_depfile_lines:
215 if not verify_inputs(line, sources, abs_build_root):
218 if dirty: # we made a change, let's write out the file
219 with action_helpers.atomic_output(args.depfile) as output:
220 output.write("\n".join(final_depfile_lines).encode("utf-8"))
223 if __name__ == '__main__':