Make writing a .sconsign more robust by writing to a temporary file first and renaming it.

3 files changed, 65 insertions, 25 deletions

diff --git a/src/CHANGES.txt b/src/CHANGES.txt
index 7ac9979..d533be9 100644
--- a/src/CHANGES.txt
+++ b/src/CHANGES.txt
@@ -36,6 +36,9 @@ RELEASE 0.05 -
   - Look up implicit (scanned) dependencies relative to the directory
     of file being scanned.
 
+  - Make writing .sconsign files more robust by first trying to write
+    to a temp file that we rename.
+
   From Anthony Roach:
 
   - Make the scons script return an error code on failures.
diff --git a/src/engine/SCons/Sig/__init__.py b/src/engine/SCons/Sig/__init__.py
index 52d8b33..d1e546f 100644
--- a/src/engine/SCons/Sig/__init__.py
+++ b/src/engine/SCons/Sig/__init__.py
@@ -29,6 +29,7 @@ The Signature package for the scons software construction utility.
 
 __revision__ = "__FILE__ __REVISION__ __DATE__ __DEVELOPER__"
 
+import os
 import os.path
 import string
 import SCons.Node
@@ -114,17 +115,38 @@ class SConsignFile:
     def write(self):
         """
         Write the .sconsign file to disk.
+
+        Try to write to a temporary file first, and rename it if we
+        succeed.  If we can't write to the temporary file, it's
+        probably because the directory isn't writable (and if so,
+        how did we build anything in this directory, anyway?), so
+        try to write directly to the .sconsign file as a backup.
+        If we can't rename, try to copy the temporary contents back
+        to the .sconsign file.  Either way, always try to remove
+        the temporary file at the end.
         """
         if self.dirty:
+            temp = os.path.join(self.dir.path, '.scons%d' % os.getpid())
             try:
+                file = open(temp, 'wt')
+                fname = temp
+            except:
                 file = open(self.sconsign, 'wt')
+                fname = self.sconsign
+            keys = self.entries.keys()
+            keys.sort()
+            for name in keys:
+                file.write("%s: %s\n" % (name, self.entries[name]))
+            file.close
+            if fname != self.sconsign:
+                try:
+                    os.rename(fname, self.sconsign)
+                except:
+                    open(self.sconsign, 'wb').write(open(fname, 'rb').read())
+            try:
+                os.unlink(temp)
             except:
                 pass
-            else:
-                keys = self.entries.keys()
-                keys.sort()
-                for name in keys:
-                    file.write("%s: %s\n" % (name, self.entries[name]))
 
 
 class Calculator:
diff --git a/test/nonwritable-sconsign.py b/test/sconsign.py
index 6955438..ac6bf2f 100644
--- a/test/nonwritable-sconsign.py
+++ b/test/sconsign.py
@@ -22,39 +22,54 @@
 # WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 #
 
-__revision__ = "test/nonwritable-sconsign.py __REVISION__ __DATE__ __DEVELOPER__"
+__revision__ = "__FILE__ __REVISION__ __DATE__ __DEVELOPER__"
 
-import TestSCons
 import os
+import TestSCons
 
 test = TestSCons.TestSCons()
 
+test.subdir('sub1', 'sub2')
+
 test.write('SConstruct', """
-env = Environment()
-env.Program(target = 'foo1', source = 'f1.c')
-""")
+def build1(target, source, env):
+    open(str(target), 'wb').write(open(str(source[0]), 'rb').read())
+    return None
 
-test.write('f1.c', r"""
-int
-main(int argc, char *argv[])
-{
-	argv[argc++] = "--";
-	printf("f1.c\n");
-	exit (0);
-}
+def build2(target, source, env):
+    import os
+    import os.path
+    open(str(target), 'wb').write(open(str(source[0]), 'rb').read())
+    dir, file = os.path.split(target)
+    os.chmod(dir, 0555)
+    return None
+
+B1 = Builder(name = "B1", action = build1)
+B2 = Builder(name = "B2", action = build2)
+env = Environment(BUILDERS = [B1, B2])
+env.B1(target = 'sub1/foo.out', source = 'foo.in')
+env.B2(target = 'sub2/foo.out', source = 'foo.in')
 """)
 
-test.write('.sconsign', "")
+test.write('foo.in', "foo.in\n")
+
+sub1__sconsign = test.workpath('sub1', '.sconsign')
+sub2__sconsign = test.workpath('sub2', '.sconsign')
 
-# For *NIX, systems, make .sconsign not writable.
+test.write(sub1__sconsign, "")
+test.write(sub2__sconsign, "")
+
+# For *NIX systems, make .sconsign not writable.
 # For Win32 systems, open it to lock it.
-os.chmod(test.workpath('.sconsign'), 0444)
-f = open(test.workpath('.sconsign'), 'r')
+os.chmod(sub1__sconsign, 0444)
+f = open(sub1__sconsign, 'r')
+
+test.run(arguments = '.')
 
-test.run(arguments = ".")
-test.run(program = test.workpath('foo1'), stdout = "f1.c\n")
+test.fail_test(test.read(sub1__sconsign) == "")
+test.fail_test(test.read(sub2__sconsign) == "")
 
-os.chmod(test.workpath('.sconsign'), 0666)
+os.chmod(sub1__sconsign, 0666)
 f.close()
 
 test.pass_test()