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..
Joseph Myers
Adhemerval Zanella