Question about fprintf

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  • vamsi
    #1

    Question about fprintf

    Hi,

    I have a program, where involves creation of a thread with stack size
    of 16k(minimum stack size). There is an fprintf statement in the
    created thread code.
    I see that there is a core dump occuring at fprintf.

    code snippet :
    *************** *************** *************** *************** *************** ******
    #include<pthrea d.h>
    #include<stdlib .h>
    #include<stdio. h>
    void func(void *);

    #define OUTSTREAM stderr

    pthread_attr_t attr;
    main()
    {
    pthread_t p[10];
    void *exitstatus;
    int i;
    pthread_attr_in it(&attr);
    if(pthread_attr _setstacksize (&attr,16ul * 1024ul))
    {
    printf("\n\n\nf ailed to set stack size");
    }
    pthread_create( &p[i],&attr,func,NUL L);

    sleep(1000);

    }
    void func(void *ptr)
    {
    int i ;
    char str[100];
    fprintf(OUTSTRE AM," FIRST :: Thread Created and here is fprintf
    \n");
    }

    core dump trace in gdb:
    Starting program: /users/a21313/fprintf/ftest_clean
    [Thread debugging using libthread_db enabled]
    [New Thread -1208084800 (LWP 32021)]
    [New Thread -1207960656 (LWP 32024)]

    Program received signal SIGSEGV, Segmentation fault.
    [Switching to Thread -1207960656 (LWP 32024)]
    0x008d1b06 in buffered_vfprin tf () from /lib/tls/libc.so.6
    (gdb) bt
    #0 0x008d1b06 in buffered_vfprin tf () from /lib/tls/libc.so.6
    #1 0x008d1deb in vfprintf () from /lib/tls/libc.so.6
    #2 0x008da40f in fprintf () from /lib/tls/libc.so.6
    #3 0x080485b0 in func (ptr=0x0) at fprintf_thread_ clean.c:28
    #4 0x00ade341 in start_thread () from /lib/tls/libpthread.so.0
    #5 0x0095efee in clone () from /lib/tls/libc.so.6

    *************** *************** *************** *************** *************** ******
    If i change stderr to stdout. the fprintf does not dump core.
    OS used : Linux 2.6.9-11.ELsmp

    Please help me.

    Thanks in advance
    Vamsi
    Tags: buffered_vfprintf, fprintf+threads
    • Nick Keighley
      #2
      Re: Question about fprintf

      On 18 Aug, 11:02, vamsi <vamsi.kom...@g mail.comwrote:
      I have a program, where involves creation of a thread with stack size
      of 16k(minimum stack size).
      and at that point you left the realm of standard C.
      Standard C has no threads or stacks. Uou nedd to try
      a Unix(?) group.

      There is an fprintf statement in the
      created thread code.
      I see that there is a core dump occuring at fprintf.
      >
      code snippet :
      *************** *************** *************** *************** *************** ­******
      #include<pthrea d.h>
      #include<stdlib .h>
      #include<stdio. h>
      void func(void *);
      >
      #define OUTSTREAM stderr
      >
      pthread_attr_t attr;
      main()
      {
              pthread_t p[10];
              void *exitstatus;
              int i;
              pthread_attr_in it(&attr);
              if(pthread_attr _setstacksize (&attr,16ul * 1024ul))
              {
                      printf("\n\n\nf ailed to set stack size");
              }
              pthread_create( &p[i],&attr,func,NUL L);
      what is i at this point? is &p[i] a valid location?
      >
              sleep(1000);
      >
      }
      >
      void func(void *ptr)
      {
              int i ;
              char str[100];
              fprintf(OUTSTRE AM," FIRST :: Thread Created and here is fprintf
      \n");
      >
      }
      >
      core dump trace in gdb:
      Starting program: /users/a21313/fprintf/ftest_clean
      [Thread debugging using libthread_db enabled]
      [New Thread -1208084800 (LWP 32021)]
      [New Thread -1207960656 (LWP 32024)]
      >
      Program received signal SIGSEGV, Segmentation fault.
      [Switching to Thread -1207960656 (LWP 32024)]
      0x008d1b06 in buffered_vfprin tf () from /lib/tls/libc.so.6
      (gdb) bt
      #0  0x008d1b06 in buffered_vfprin tf () from /lib/tls/libc.so.6
      #1  0x008d1deb in vfprintf () from /lib/tls/libc.so.6
      #2  0x008da40f in fprintf () from /lib/tls/libc.so.6
      #3  0x080485b0 in func (ptr=0x0) at fprintf_thread_ clean.c:28
      #4  0x00ade341 in start_thread () from /lib/tls/libpthread.so.0
      #5  0x0095efee in clone () from /lib/tls/libc.so.6
      >
      *************** *************** *************** *************** *************** ­******
      If i change stderr to stdout. the fprintf does not dump core.
      OS used : Linux 2.6.9-11.ELsmp

      --
      Nick Keighley

        Comment

        • vamsi
          #3
          Re: Question about fprintf

          On Aug 18, 3:11 pm, Nick Keighley <nick_keighley_ nos...@hotmail. com>
          wrote:
          On 18 Aug, 11:02, vamsi <vamsi.kom...@g mail.comwrote:
          >
          I have a program, where involves creation of a thread with stack size
          of 16k(minimum stack size).
          >
          and at that point you left the realm of standard C.
          Standard C has no threads or stacks. Uou nedd to try
          a Unix(?) group.
          >
          >
          >
          There is an fprintf statement in the
          created thread code.
          I see that there is a core dump occuring at fprintf.
          >
          code snippet :
          *************** *************** *************** *************** *************** ­******
          #include<pthrea d.h>
          #include<stdlib .h>
          #include<stdio. h>
          void func(void *);
          >
          #define OUTSTREAM stderr
          >
          pthread_attr_t attr;
          main()
          {
          pthread_t p[10];
          void *exitstatus;
          int i;
          pthread_attr_in it(&attr);
          if(pthread_attr _setstacksize (&attr,16ul * 1024ul))
          {
          printf("\n\n\nf ailed to set stack size");
          }
          pthread_create( &p[i],&attr,func,NUL L);
          >
          what is i at this point? is &p[i] a valid location?
          >
          >
          >
          >
          >
          sleep(1000);
          >
          }
          >
          void func(void *ptr)
          {
          int i ;
          char str[100];
          fprintf(OUTSTRE AM," FIRST :: Thread Created and here is fprintf
          \n");
          >
          }
          >
          core dump trace in gdb:
          Starting program: /users/a21313/fprintf/ftest_clean
          [Thread debugging using libthread_db enabled]
          [New Thread -1208084800 (LWP 32021)]
          [New Thread -1207960656 (LWP 32024)]
          >
          Program received signal SIGSEGV, Segmentation fault.
          [Switching to Thread -1207960656 (LWP 32024)]
          0x008d1b06 in buffered_vfprin tf () from /lib/tls/libc.so.6
          (gdb) bt
          #0 0x008d1b06 in buffered_vfprin tf () from /lib/tls/libc.so.6
          #1 0x008d1deb in vfprintf () from /lib/tls/libc.so.6
          #2 0x008da40f in fprintf () from /lib/tls/libc.so.6
          #3 0x080485b0 in func (ptr=0x0) at fprintf_thread_ clean.c:28
          #4 0x00ade341 in start_thread () from /lib/tls/libpthread.so.0
          #5 0x0095efee in clone () from /lib/tls/libc.so.6
          >
          *************** *************** *************** *************** *************** ­******
          If i change stderr to stdout. the fprintf does not dump core.
          OS used : Linux 2.6.9-11.ELsmp
          >
          --
          Nick Keighley
          i=0; even then it dumps core. I shall try posting in other groups as
          well.

            Comment

            • Richard Tobin
              #4
              Re: Question about fprintf

              In article <6bcf1c70-3a4e-4cd8-bfea-499bbd028049@v1 g2000pra.google groups.com>,
              vamsi <vamsi.komati@g mail.comwrote:
              if(pthread_attr _setstacksize (&attr,16ul * 1024ul))
              An obvious possibility is that this stack size is too small. Have
              you tried other sizes, or using the default size?

              -- Richard
              --
              Please remember to mention me / in tapes you leave behind.

                Comment

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