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

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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.

	* 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..
This commit is contained in:
Adhemerval Zanella
2016-04-26 17:40:25 -03:00
parent 085bbece2c
commit f9123b5003
4 changed files with 83 additions and 4 deletions
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6
libio/fmemopen.c
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@ -86,10 +86,10 @@ fmemopen_write (void *cookie, const char *b, size_t s)
memcpy (&(c->buffer[pos]), b, s);
pos += s;
if ((size_t) pos > c->maxpos)
c->pos += s;
if ((size_t) c->pos > c->maxpos)
{
c->maxpos = pos;
c->maxpos = c->pos;
if (addnullc)
c->buffer[c->maxpos] = '\0';
}