[Bug libstdc++/65663] New: libstdc++: writing mixed-size blocks through an std::ofstream to a SMB 2.1 share produces file corruption

kkananen at gmail dot com gcc-bugzilla@gcc.gnu.org
Thu Apr 2 16:07:00 GMT 2015


https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65663

            Bug ID: 65663
           Summary: libstdc++: writing mixed-size blocks through an
                    std::ofstream to a SMB 2.1 share produces file
                    corruption
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kkananen at gmail dot com

Created attachment 35216
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35216&action=edit
Preprocessed minimum-repro.ii

Basic description of the problem:
Application writing into a libstdc++ ofstream from a Mac OS X 10.9 or 10.10
host to a samba shared folder hosted on Windows 7/8/2008 Server (the
combination of OS X + Windows has to support SMB 2.1) can produce file
corruption.

Reproductions steps:
You need two PCs visible to each other in a network: 
  a. a Mac running OS X 10.9 or later
  b. a Windows 7, Windows Server 2008 R2 or later PC.

1. Share a test folder on the Windows PC so that it is visible for the Mac in 
  the network

2. Connect the Mac to the windows shared folder using the smb protocol:
  e.g. in OSX Finder, connect to server smb://name-of-windows-pc/name-of-share
  (the share should now be visible under /Volumes/name-of-share/)

3. Compile this application on the Mac against libstdc++
  e.g. apple clang 5.0:
    clang++ ./minimum-repro.cpp -stdlib=libstdc++ -o minimum-repro
       g++ (4.0 or later):
    g++ ./minimum-repro.cpp -o minimum-repro

4. Run the compiled app on the Mac, with a single argument, a path to a file on
the 
  network share:
  e.g. ./minimum-repro /Volumes/name-of-share/corruption-test.txt


The file will be written and it's contents read back and checked against the
reference - they will not match in contents, i.e. the file has been corrupted
on write.


The key to bug reproduction is to first write a small block of data (< 1022
bytes) and then a large block (> 0.5 MB) into an ofstream opened on the shared
folder. The file will be corrupt from the 0.5 MB mark onwards.

Flushing the ofstream between the writes, writing smaller blocks all make the
problem go away.


Built on OS X 10.8.5 and 10.9 with g++ 4.0.1, 4.2.1 and apple clang 5.0 and 5.1
using libstdc++ (6.0.9).

Tested on OS X 10.9, 10.10 (host) and Windows 7 and 8 (file server).

Version information:
$ g++-4.0 -v
Using built-in specs.
Target: i686-apple-darwin10
Configured with: /var/tmp/gcc_40/gcc_40-5494~315/src/configure
--disable-checking -enable-werror --prefix=/usr --mandir=/share/man
--enable-languages=c,objc,c++,obj-c++
--program-transform-name=/^[cg][^.-]*$/s/$/-4.0/
--with-gxx-include-dir=/include/c++/4.0.0 --with-slibdir=/usr/lib
--build=i686-apple-darwin10 --with-arch=apple --with-tune=generic
--host=i686-apple-darwin10 --target=i686-apple-darwin10
Thread model: posix
gcc version 4.0.1 (Apple Inc. build 5494)

$ g++-4.2 -v
Using built-in specs.
Target: i686-apple-darwin10
Configured with: /var/tmp/gcc/gcc-5666.3~6/src/configure --disable-checking
--enable-werror --prefix=/usr --mandir=/share/man
--enable-languages=c,objc,c++,obj-c++
--program-transform-name=/^[cg][^.-]*$/s/$/-4.2/ --with-slibdir=/usr/lib
--build=i686-apple-darwin10 --program-prefix=i686-apple-darwin10-
--host=x86_64-apple-darwin10 --target=i686-apple-darwin10
--with-gxx-include-dir=/include/c++/4.2.1
Thread model: posix
gcc version 4.2.1 (Apple Inc. build 5666) (dot 3)

$ clang++ -v
Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn)
Target: x86_64-apple-darwin13.0.0
Thread model: posix

$ clang++ -v
Apple LLVM version 5.1 (clang-503.0.40) (based on LLVM 3.4svn)
Target: x86_64-apple-darwin12.5.0
Thread model: posix


Command-line to compile:
g++: g++ ./minimum-repro.cpp -o ./minimum-repro
clang: clang++ ./minimum-repro.cpp -stdlib=libstdc++ -o ./minimum-repro



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