strange problem opening ofstream

Discussion in 'C++' started by rrsettgast@gmail.com, Feb 8, 2008.

  1. Guest

    Hi all,
    I am having a really odd problem. My code is spitting out a bunch of
    binary files through ofstream. Actually, I have a little wrapper for
    binary ofstream operations....where ofstream is a member of the
    wrapper (i.e. not a derived class). At some point during the
    execution, my program stops writing output files. The ofstream::eek:pen()
    function is failing. The failbit is true. After the fail, I can't even
    open a standard ofstream in the same function....but my ofstreams are
    fine in other parts of the code. And the kicker is that when I run the
    same executable through eclipse's debugger without any breakpoints,
    everything works like I think it should. This is above my head. Any
    suggestions would be appreciated.

    Thanks
    Randy
    p.s. I am using g++4.2 on OSX.
     
    , Feb 8, 2008
    #1
    1. Advertising

  2. Daniel T. Guest

    wrote:

    > I am having a really odd problem. My code is spitting out a bunch of
    > binary files through ofstream. Actually, I have a little wrapper for
    > binary ofstream operations....where ofstream is a member of the
    > wrapper (i.e. not a derived class). At some point during the
    > execution, my program stops writing output files. The ofstream::eek:pen()
    > function is failing. The failbit is true. After the fail, I can't even
    > open a standard ofstream in the same function....but my ofstreams are
    > fine in other parts of the code. And the kicker is that when I run the
    > same executable through eclipse's debugger without any breakpoints,
    > everything works like I think it should. This is above my head. Any
    > suggestions would be appreciated.


    How many is "a bunch"? Are you sure they are all getting closed properly?
     
    Daniel T., Feb 8, 2008
    #2
    1. Advertising

  3. Guest

    Hi,
    Like 10.
    Yes they are all closed.
    I do the following commands:
    cout<<" output.is_open() = "<<output.is_open()<<endl;
    cout<<" output.fail() = "<<output.fail()<<endl;
    cout<<" output.bad() = "<<output.bad()<<endl;
    cout<<" output.good() = "<<output.good()<<endl;
    before and after the output.open( filename , ios::binary | ios::eek:ut |
    ios::trunc ); call.
    i get:
    before open command
    output.is_open() = 0
    output.fail() = 0
    output.bad() = 0
    output.good() = 1
    after open command
    output.is_open() = 0
    output.fail() = 1
    output.bad() = 0
    output.good() = 0

    Any way to tell exactly why the open fails?

    Thanks again.

    On Feb 8, 11:24 am, "Daniel T." <> wrote:
    > How many is "a bunch"? Are you sure they are all getting closed properly?
     
    , Feb 8, 2008
    #3
  4. James Kanze Guest

    On Feb 8, 8:50 pm, wrote:

    > On Feb 8, 11:24 am, "Daniel T." <> wrote:


    > > How many is "a bunch"? Are you sure they are all getting closed properly?


    > Like 10.
    > Yes they are all closed.
    > I do the following commands:
    > cout<<" output.is_open() = "<<output.is_open()<<endl;
    > cout<<" output.fail() = "<<output.fail()<<endl;
    > cout<<" output.bad() = "<<output.bad()<<endl;
    > cout<<" output.good() = "<<output.good()<<endl;
    > before and after the output.open( filename , ios::binary | ios::eek:ut |
    > ios::trunc ); call.
    > i get:
    > before open command
    > output.is_open() = 0
    > output.fail() = 0
    > output.bad() = 0
    > output.good() = 1
    > after open command
    > output.is_open() = 0
    > output.fail() = 1
    > output.bad() = 0
    > output.good() = 0


    > Any way to tell exactly why the open fails?


    Not portably, but on most implementations, reading errno
    immediately after the open fails (without any intervening code)
    will give a good idea. Something like:

    stream.open( filename ) ;
    if ( ! stream ) {
    int err = errno ;
    std::cerr << "open of " << filename << " failed: "
    << strerror( err ) << std::endl ;
    }

    One note, however: in your original posting, you said you were
    outputting binary files. Are you sure ofstream is the right
    tool; it does text formatting, not binary (and it seems a bit
    overweight if the only function in it you use is write()).

    --
    James Kanze (GABI Software) email:
    Conseils en informatique orientée objet/
    Beratung in objektorientierter Datenverarbeitung
    9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34
     
    James Kanze, Feb 8, 2008
    #4
  5. Daniel T. Guest

    wrote:

    > Like 10.
    > Yes they are all closed.
    > I do the following commands:
    > cout<<" output.is_open() = "<<output.is_open()<<endl;
    > cout<<" output.fail() = "<<output.fail()<<endl;
    > cout<<" output.bad() = "<<output.bad()<<endl;
    > cout<<" output.good() = "<<output.good()<<endl;
    > before and after the output.open( filename , ios::binary | ios::eek:ut |
    > ios::trunc ); call.
    > i get:
    > before open command
    > output.is_open() = 0
    > output.fail() = 0
    > output.bad() = 0
    > output.good() = 1
    > after open command
    > output.is_open() = 0
    > output.fail() = 1
    > output.bad() = 0
    > output.good() = 0
    >
    > Any way to tell exactly why the open fails?
    >
    > Thanks again.


    OK, I just ran a program on OS X using gcc 4 and opened 253 files
    simultaneously with no problems. Your going to have to give more details.

    Here's what I did:

    // in the below I am using some non-standard stuff...
    // c_array: is a class implementing a static array that conforms to
    // the Random Access Container concept
    // for_each: the one I'm using is non-standard. It takes two ranges
    // and performs a binary-op on them, then returns the binary-op
    // object.
    // range: is an iterator over nonnegative integers. I.e., 0, 1, 2, ...

    void test( ofstream& output, int i ) {
    cout << i << ' ';
    assert( output.is_open() == false );
    assert( output.fail() == false );
    assert( output.bad() == false );
    assert( output.good() == true );
    stringstream ss;
    ss << "foobar " << i << ".txt";
    output.open( ss.str().c_str() );
    assert( output.is_open() == true );
    assert( output.fail() == false );
    assert( output.bad() == false );
    assert( output.good() == true );
    }

    int main() {
    const int total = 1000;
    c_array<ofstream, total> files;
    for_each( files.begin(), files.end(), range( total ), &test );
    cout << endl;
    }

    The output:

    0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
    27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
    51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74
    75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98
    99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116
    117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134
    135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152
    153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170
    171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188
    189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206
    207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224
    225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242
    243 244 245 246 247 248 249 250 251 252 253

    failed assertion `output.is_open() == true'
     
    Daniel T., Feb 8, 2008
    #5
  6. Guest

    Hi,
    Thanks for your suggestions. I will try this today. As you have
    probably figured out, I am not an engineer first, and a programmer
    second. Your suggestion about ofstream being the wrong tool has come
    time mind before, but I wouldn't know what else to use...besides a
    standard C stream....or just an fstream? So yes i just write binary
    files....what would be a more appropriate tool?

    Thanks
    Randy

    On Feb 8, 12:35 pm, James Kanze <> wrote:
    > On Feb 8, 8:50 pm, wrote:
    >
    >
    >
    > > On Feb 8, 11:24 am, "Daniel T." <> wrote:
    > > > How many is "a bunch"? Are you sure they are all getting closed properly?

    > > Like 10.
    > > Yes they are all closed.
    > > I do the following commands:
    > > cout<<" output.is_open() = "<<output.is_open()<<endl;
    > > cout<<" output.fail() = "<<output.fail()<<endl;
    > > cout<<" output.bad() = "<<output.bad()<<endl;
    > > cout<<" output.good() = "<<output.good()<<endl;
    > > before and after the output.open( filename , ios::binary | ios::eek:ut |
    > > ios::trunc ); call.
    > > i get:
    > > before open command
    > > output.is_open() = 0
    > > output.fail() = 0
    > > output.bad() = 0
    > > output.good() = 1
    > > after open command
    > > output.is_open() = 0
    > > output.fail() = 1
    > > output.bad() = 0
    > > output.good() = 0
    > > Any way to tell exactly why the open fails?

    >
    > Not portably, but on most implementations, reading errno
    > immediately after the open fails (without any intervening code)
    > will give a good idea. Something like:
    >
    > stream.open( filename ) ;
    > if ( ! stream ) {
    > int err = errno ;
    > std::cerr << "open of " << filename << " failed: "
    > << strerror( err ) << std::endl ;
    > }
    >
    > One note, however: in your original posting, you said you were
    > outputting binary files. Are you sure ofstream is the right
    > tool; it does text formatting, not binary (and it seems a bit
    > overweight if the only function in it you use is write()).
    >
    > --
    > James Kanze (GABI Software) email:
    > Conseils en informatique orientée objet/
    > Beratung in objektorientierter Datenverarbeitung
    > 9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34
     
    , Feb 11, 2008
    #6
  7. James Kanze Guest

    On Feb 11, 5:32 pm, wrote:

    > Thanks for your suggestions. I will try this today. As you
    > have probably figured out, I am not an engineer first, and a
    > programmer second. Your suggestion about ofstream being the
    > wrong tool has come time mind before, but I wouldn't know what
    > else to use...besides a standard C stream....or just an
    > fstream? So yes i just write binary files....what would be a
    > more appropriate tool?


    A binary stream, not a text stream. There isn't one in the
    standard, because there are so many different binary formats.
    Implementing one that would be 100% portable can be somewhat
    difficult (especially for floating points), but most of the
    time, you don't need that degree of portability. (You do still
    need to know something about how the iostreams work, since you'd
    definitely want to use streambuf and its derived classes, and
    probably basic_ios for the error handling as well.)

    --
    James Kanze (GABI Software) email:
    Conseils en informatique orientée objet/
    Beratung in objektorientierter Datenverarbeitung
    9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34
     
    James Kanze, Feb 12, 2008
    #7
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Tom Johnson
    Replies:
    4
    Views:
    395
    red floyd
    Aug 15, 2003
  2. Armando
    Replies:
    2
    Views:
    7,122
    Martijn Lievaart
    Jan 23, 2004
  3. Alfons
    Replies:
    1
    Views:
    456
  4. Squid Seven

    ofstream * vs. ofstream

    Squid Seven, Jul 13, 2005, in forum: C++
    Replies:
    5
    Views:
    625
    Ivan Johansen
    Jul 14, 2005
  5. fniles
    Replies:
    0
    Views:
    290
    fniles
    Apr 26, 2009
Loading...

Share This Page