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[Bug stdio/20005] fflush on a file opened with fmemopen resets position to 0


https://sourceware.org/bugzilla/show_bug.cgi?id=20005

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The branch, release/2.23/master has been updated
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       via  c2fba3b047c2fac50985a47ff96075b5d9078432 (commit)
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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=321e1cef26ccbece949b16622ef74c203bd8ecc6

commit 321e1cef26ccbece949b16622ef74c203bd8ecc6
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Wed Apr 27 11:51:01 2016 -0300

    libio: Fix fmemopen append mode failure (BZ# 20012)

    The fmemopen implementation does not account the file position correctly in
    append mode. The following example shows the failure:

    ===
    int main ()
    {
      char buf[10] = "test";
      FILE *fp = fmemopen (buf, 10, "a+");
      fseek (fp, 0, SEEK_SET);

      int gr;
      if ((gr = getc (fp)) != 't' ||
          (gr = getc (fp)) != 'e' ||
          (gr = getc (fp)) != 's' ||
          (gr = getc (fp)) != 't' ||
          (gr = getc (fp)) != EOF)
        {
          printf ("%s: getc failed returned %i\n", __FUNCTION__, gr);
          return 1;
        }

      return 0;
    }
    ===

    This is due both how read and write operation update the buffer position,
    taking in consideration buffer lenght instead of maximum position defined
    by the open mode.  This patch fixes it and also fixes fseek not returning
    EINVAL for invalid whence modes.

    Tested on x86_64 and i686.

    This is a backport of b65b205fbcabbb02463e31df17f5cabf7556f892.

        [BZ #20012]
        * libio/fmemopen.c (fmemopen_read): Use buffer maximum position, not
        length to calculate the buffer to read.
        (fmemopen_write): Set the buffer position based on bytes written.
        (fmemopen_seek): Return EINVAL for invalid whence modes.

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=c2fba3b047c2fac50985a47ff96075b5d9078432

commit c2fba3b047c2fac50985a47ff96075b5d9078432
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Tue Apr 26 17:40:25 2016 -0300

    libio: Update internal fmemopen position after write (BZ #20005)

    Current GLIBC fmemopen fails with a simple testcase:

      char buffer[500] = "x";
      FILE *stream;
      stream = fmemopen(buffer, 500, "r+");
      fwrite("fish",sizeof(char),5,stream);
      printf("pos-1:%ld\n",ftell(stream));
      fflush(stream);
      printf("pos-2:%ld\n",ftell(stream));

    It returns:

      pos-1:5
      pos-2:0

    Where it should return:

      pos-1:5
      pos-2:5

    This is due the internal write function does not correctly update the
internal
    object position state and then the seek operation returns a wrong value. 
This
    patch fixes it.

    It fixes both BZ #20005 and BZ #19230 (marked as duplicated). A new test is
    added to check for such case.

    Tested on x86_64 and i686.

    This is a backport of f9123b5003e62b6e54996076e860f23aee9a0593.

        * libio/fmemopen.c (fmemopen_write): Update internal position after
        write.
        * stdio-common/Makefile (tests): Add tst-fmemopen4.c.
        * stdio-common/tst-fmemopen4.c: New file..

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                                          |   14 +++
 libio/fmemopen.c                                   |   32 +++---
 stdio-common/Makefile                              |    2 +-
 stdio-common/tst-fmemopen3.c                       |  118 +++++++++++++++++++-
 .../tst-rwlock13.c => stdio-common/tst-fmemopen4.c |   41 ++++----
 5 files changed, 170 insertions(+), 37 deletions(-)
 copy nptl/tst-rwlock13.c => stdio-common/tst-fmemopen4.c (53%)

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