bootstrap: write texts to a .tmp file first for atomicity

If you are using a hard-linked file as your config.toml, this change will affect the way other instances of the file is modified.
The original version would modify all other instances whereas the new version will leave others unchanged, reducing the ref count by one.

Signed-off-by: NODA, Kai <nodakai@gmail.com>

diff --git a/src/bootstrap/bootstrap.py b/src/bootstrap/bootstrap.py
index 512d4d8c5b792ce0e1958574ff59e0168996793c..d1aa32236aeeebde54e81b5a03d4ec40b3d917a3 100644 (file)
--- a/src/bootstrap/bootstrap.py
+++ b/src/bootstrap/bootstrap.py
@@ -303,6 +303,14 @@ def default_build_triple():
     return "{}-{}".format(cputype, ostype)
 
 
+@contextlib.contextmanager
+def output(filepath):
+    tmp = filepath + '.tmp'
+    with open(tmp, 'w') as f:
+        yield f
+    os.rename(tmp, filepath)
+
+
 class RustBuild(object):
     """Provide all the methods required to build Rust"""
     def __init__(self):
@@ -346,7 +354,7 @@ class RustBuild(object):
             self._download_stage0_helper(filename, "rustc")
             self.fix_executable("{}/bin/rustc".format(self.bin_root()))
             self.fix_executable("{}/bin/rustdoc".format(self.bin_root()))
-            with open(self.rustc_stamp(), 'w') as rust_stamp:
+            with output(self.rustc_stamp()) as rust_stamp:
                 rust_stamp.write(self.date)
 
             # This is required so that we don't mix incompatible MinGW
@@ -363,7 +371,7 @@ class RustBuild(object):
             filename = "cargo-{}-{}.tar.gz".format(cargo_channel, self.build)
             self._download_stage0_helper(filename, "cargo")
             self.fix_executable("{}/bin/cargo".format(self.bin_root()))
-            with open(self.cargo_stamp(), 'w') as cargo_stamp:
+            with output(self.cargo_stamp()) as cargo_stamp:
                 cargo_stamp.write(self.date)
 
     def _download_stage0_helper(self, filename, pattern):
@@ -776,7 +784,7 @@ def bootstrap(help_triggered):
     if build.use_vendored_sources:
         if not os.path.exists('.cargo'):
             os.makedirs('.cargo')
-        with open('.cargo/config', 'w') as cargo_config:
+        with output('.cargo/config') as cargo_config:
             cargo_config.write("""
                 [source.crates-io]
                 replace-with = 'vendored-sources'

diff --git a/src/bootstrap/configure.py b/src/bootstrap/configure.py
index 80fa96509bd87f2a13cd563ebfd4086fdef2a306..9fdba044f4be3da82b035e5bc110c4a477f9085d 100755 (executable)
--- a/src/bootstrap/configure.py
+++ b/src/bootstrap/configure.py
@@ -432,7 +432,7 @@ for section_key in config:
 # order that we read it in.
 p("")
 p("writing `config.toml` in current directory")
-with open('config.toml', 'w') as f:
+with bootstrap.output('config.toml') as f:
     for section in section_order:
         if section == 'target':
             for target in targets:
@@ -442,7 +442,7 @@ with open('config.toml', 'w') as f:
             for line in sections[section]:
                 f.write(line + "\n")
 
-with open('Makefile', 'w') as f:
+with bootstrap.output('Makefile') as f:
     contents = os.path.join(rust_dir, 'src', 'bootstrap', 'mk', 'Makefile.in')
     contents = open(contents).read()
     contents = contents.replace("$(CFG_SRC_DIR)", rust_dir + '/')