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203 lines
8.3 KiB
Python
Executable file
203 lines
8.3 KiB
Python
Executable file
#!/usr/bin/env python
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# Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
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#
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# The Rust compiler normally builds source code directly into an executable.
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# Internally, object code is produced, and then the (system) linker is called,
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# but this all happens under the covers.
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#
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# However Deno's build system uses it's own linker. For it to successfully
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# produce an executable from rustc-generated object code, it needs to link
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# with a dozen or so "built-in" Rust libraries (as in: not Cargo crates),
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# and we need to tell the linker which and where those .rlibs are.
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#
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# Hard-coding these libraries into the GN configuration isn't possible: the
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# required .rlib files have some sort of hash code in their file name, and their
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# location depends on how Rust is set up, and which toolchain is active.
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#
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# So instead, we have this script: it writes a list of linker options (ldflags)
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# to stdout, separated by newline characters. It is called from `rust.gni` when
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# GN is generating ninja files (it doesn't run in the build phase).
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#
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# There is no official way through which rustc will give us the information
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# we need, so a "back door" is used. We tell `rustc` to compile a (dummy)
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# program, and to use a custom linker. This "linker" doesn't actually link
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# anything; it just dumps it's argv to a temporary file. When rustc is done,
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# this script then reads the linker arguments from that temporary file, and
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# then filters it to remove flags that are irrelevant or undesirable.
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import json
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import re
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import sys
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import os
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from os import path
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import subprocess
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import tempfile
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def capture_linker_args(argsfile_path):
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with open(argsfile_path, "wb") as argsfile:
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argsfile.write("\n".join(sys.argv[1:]))
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def get_ldflags(rustc_args):
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# Prepare the environment for rustc.
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rustc_env = os.environ.copy()
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# We'll capture the arguments rustc passes to the linker by telling it
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# that this script *is* the linker.
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# On Posix systems, this file is directly executable thanks to it's shebang.
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# On Windows, we use a .cmd wrapper file.
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if os.name == "nt":
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rustc_linker_base, _rustc_linker_ext = path.splitext(__file__)
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rustc_linker = rustc_linker_base + ".cmd"
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else:
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rustc_linker = __file__
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# Make sure that when rustc invokes this script, it uses the same version
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# of the Python interpreter as we're currently using. On Posix systems this
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# is done making the Python directory the first element of PATH.
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# On Windows, the wrapper script uses the PYTHON_EXE environment variable.
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if os.name == "nt":
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rustc_env["PYTHON_EXE"] = sys.executable
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else:
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python_dir = path.dirname(sys.executable)
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rustc_env["PATH"] = python_dir + path.pathsep + os.environ["PATH"]
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# Create a temporary file to write captured Rust linker arguments to.
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# Unfortunately we can't use tempfile.NamedTemporaryFile here, because the
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# file it creates can't be open in two processes at the same time.
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argsfile_fd, argsfile_path = tempfile.mkstemp()
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rustc_env["ARGSFILE_PATH"] = argsfile_path
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try:
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# Build the rustc command line.
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# * `-Clinker=` tells rustc to use our fake linker.
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# * `-Csave-temps` prevents rustc from deleting object files after
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# linking. We need to preserve the extra object file with allocator
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# symbols (`_rust_alloc` etc.) in it that rustc produces.
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rustc_cmd = [
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"rustc",
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"-Clinker=" + rustc_linker,
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"-Csave-temps",
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] + rustc_args
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# Spawn the rust compiler.
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rustc_proc = subprocess.Popen(
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rustc_cmd,
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env=rustc_env,
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stdout=subprocess.PIPE,
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stderr=subprocess.STDOUT)
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# Forward rustc's output to stderr.
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for line in rustc_proc.stdout:
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# Suppress the warning:
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# `-C save-temps` might not produce all requested temporary
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# products when incremental compilation is enabled.
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# It's pointless, because incremental compilation is disabled.
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if re.match(r"^warning:.*save-temps.*incremental compilation",
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line):
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continue
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# Also, do not write completely blank lines to stderr.
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if line.strip() == "":
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continue
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sys.stderr.write(line)
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# The rustc process should return zero. If not, raise an exception.
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rustc_retcode = rustc_proc.wait()
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if rustc_retcode != 0:
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raise subprocess.CalledProcessError(rustc_retcode, rustc_cmd)
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# Read captured linker arguments from argsfile.
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argsfile_size = os.fstat(argsfile_fd).st_size
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argsfile_content = os.read(argsfile_fd, argsfile_size)
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args = argsfile_content.split("\n")
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except OSError as e: # Note: in python 3 this will be a FileNotFoundError.
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print "Error executing rustc command (is rust installed?):"
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print " ".join(rustc_cmd) + "\n"
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raise e
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finally:
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# Close and delete the temporary file.
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os.close(argsfile_fd)
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os.unlink(argsfile_path)
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# From the list of captured linker arguments, build the list of ldflags that
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# we actually need.
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ldflags = []
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next_arg_is_flag_value = False
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for arg in args:
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# Note that within the following if/elif blocks, `pass` means that
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# that captured arguments gets included in `ldflags`. The final `else`
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# clause filters out unrecognized/unwanted flags.
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if next_arg_is_flag_value:
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# We're looking at a value that follows certain parametric flags,
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# e.g. the path in '-L <path>'.
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next_arg_is_flag_value = False
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elif arg.endswith(".rlib"):
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# Built-in Rust library, e.g. `libstd-8524caae8408aac2.rlib`.
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pass
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elif re.match(r"^empty_crate\.[a-z0-9]+\.rcgu.o$", arg):
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# This file is needed because it contains certain allocator
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# related symbols (e.g. `__rust_alloc`, `__rust_oom`).
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# The Rust compiler normally generates this file just before
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# linking an executable. We pass `-Csave-temps` to rustc so it
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# doesn't delete the file when it's done linking.
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pass
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elif arg.endswith(".crate.allocator.rcgu.o"):
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# Same as above, but for rustc version 1.29.0 and older.
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pass
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elif arg.endswith(".lib") and not arg.startswith("msvcrt"):
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# Include most Windows static/import libraries (e.g. `ws2_32.lib`).
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# However we ignore Rusts choice of C runtime (`mvcrt*.lib`).
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# Rust insists on always using the release "flavor", even in debug
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# mode, which causes conflicts with other libraries we link with.
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pass
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elif arg.upper().startswith("/LIBPATH:"):
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# `/LIBPATH:<path>`: Linker search path (Microsoft style).
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pass
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elif arg == "-l" or arg == "-L":
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# `-l <name>`: Link with library (GCC style).
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# `-L <path>`: Linker search path (GCC style).
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next_arg_is_flag_value = True # Ensure flag argument is captured.
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elif arg == "-Wl,--start-group" or arg == "-Wl,--end-group":
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# Start or end of an archive group (GCC style).
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pass
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else:
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# Not a flag we're interested in -- don't add it to ldflags.
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continue
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ldflags += [arg]
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return ldflags
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def get_version():
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version = subprocess.check_output(["rustc", "--version"])
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version = version.strip() # Remove trailing newline.
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return version
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def main():
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# If ARGSFILE_PATH is set this script is being invoked by rustc, which
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# thinks we are a linker. All we do now is write our argv to the specified
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# file and exit. Further processing is done by our grandparent process,
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# also this script but invoked by gn.
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argsfile_path = os.getenv("ARGSFILE_PATH")
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if argsfile_path is not None:
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return capture_linker_args(argsfile_path)
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empty_crate_source = path.join(path.dirname(__file__), "empty_crate.rs")
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info = {
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"version": get_version(),
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"ldflags_bin": get_ldflags([empty_crate_source]),
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"ldflags_test": get_ldflags([empty_crate_source, "--test"])
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}
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# Write the information dict as a json object.
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json.dump(info, sys.stdout)
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if __name__ == '__main__':
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sys.exit(main())
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