Write coredata transactionally. Closes #3511.

mesonbuild/coredata.py

@@ -354,10 +354,19 @@ def load(build_dir):
 
 def save(obj, build_dir):
     filename = os.path.join(build_dir, 'meson-private', 'coredata.dat')
+    prev_filename = filename + '.prev'
+    tempfilename = filename + '~'
     if obj.version != version:
         raise MesonException('Fatal version mismatch corruption.')
-    with open(filename, 'wb') as f:
+    if os.path.exists(filename):
+        import shutil
+        shutil.copyfile(filename, prev_filename)
+    with open(tempfilename, 'wb') as f:
         pickle.dump(obj, f)
+        f.flush()
+        os.fsync(f.fileno())
+    os.replace(tempfilename, filename)
+    return filename
 
 def get_builtin_options():
     return list(builtin_options.keys())

mesonbuild/environment.py

@@ -261,7 +261,6 @@ def search_version(text):
 class Environment:
     private_dir = 'meson-private'
     log_dir = 'meson-logs'
-    coredata_file = os.path.join(private_dir, 'coredata.dat')
 
     def __init__(self, source_dir, build_dir, main_script_launcher, options, original_cmd_line_args):
         self.source_dir = source_dir
@@ -335,8 +334,7 @@ class Environment:
         return self.cross_info is not None
 
     def dump_coredata(self):
-        coredata.save(self.coredata, self.get_build_dir())
-        return os.path.join(self.get_build_dir(), Environment.coredata_file)
+        return coredata.save(self.coredata, self.get_build_dir())
 
     def get_script_dir(self):
         import mesonbuild.scripts

mesonbuild/mesonmain.py

@@ -204,7 +204,11 @@ class MesonApp:
             g.run_postconf_scripts()
         except:
             if 'cdf' in locals():
-                os.unlink(cdf)
+                old_cdf = cdf + '.prev'
+                if os.path.exists(old_cdf):
+                    os.replace(old_cdf, cdf)
+                else:
+                    os.unlink(cdf)
             raise
 
 def run_script_command(args):