Sorry it keeps failing if I send the git diff in the attachment. I will try
copy the text again.
git diffdiff --git a/winsup/cygwin/fhandler_disk_file.cc
b/winsup/cygwin/fhandler_disk_file.ccindex bc8fead..525cb32 100644---
a/winsup/cygwin/fhandler_disk_file.cc+++
b/winsup/cygwin/fhandler_disk_file.cc@@ -1525,6 +1525,7 @@
fhandler_disk_file::pread (void *buf, size_t count, off_t offset)
IO_STATUS_BLOCK io;
LARGE_INTEGER off = { QuadPart:offset };
+ memset(&io, 0, sizeof(io));
if (!prw_handle && prw_open (false)) goto
non_atomic;
status = NtReadFile (prw_handle, NULL, NULL, NULL, &io, buf,
count,
On Monday, November 6, 2017, 12:23:44 PM PST, Corinna Vinschen
<corinna-cyg...@cygwin.com> wrote:
Hi,
On Nov 6 19:20, Xiaofeng Liu via cygwin-patches wrote:
> pread() return 0 if read beyond end of file in linux, but not zero in cygwin.
> I have a small code to show the problem:
> #include <sys/types.h>
> #include <sys/stat.h>
> #include <fcntl.h>
> #include <unistd.h>
> #include <stdio.h>
> #include <errno.h>
>
> int main()
> {
> const char* file = "/home/xliu/work/exome/a.bam";
> struct stat st;
> stat(file, &st);
> char buf[65536];
> int fd = open(file, O_RDONLY);
> int ret = pread(fd, buf, sizeof buf, st.st_size);
> fprintf(stderr, "filesize %ld, after eof pread() return = %d, errno = %d\n",
>st.st_size, ret, errno);
> lseek(fd, st.st_size, SEEK_SET);
> ret = read(fd, buf, sizeof buf);
> fprintf(stderr, "filesize %ld, after eof read() return = %d, errno = %d\n",
>st.st_size, ret, errno);
> }
> $ ./a.exe
> filesize 6126093048, after eof pread() return = 3, errno = 0
> filesize 6126093048, after eof read() return = 0, errno = 0
> The issue is that NtReadFile() return EOF status, but doesn't set
> io.information to 0. As a result, the current pread() implementation could
> return an arbitrary number in the stack. The fix is a one line fix: reset io
> status block.
> diff --git a/winsup/cygwin/fhandler_disk_file.cc
> b/winsup/cygwin/fhandler_disk_file.ccindex bc8fead..525cb32 100644---
> a/winsup/cygwin/fhandler_disk_file.cc+++
> b/winsup/cygwin/fhandler_disk_file.cc@@ -1525,6 +1525,7 @@
> fhandler_disk_file::pread (void *buf, size_t count, off_t offset)
> IO_STATUS_BLOCK io; LARGE_INTEGER off = { QuadPart:offset };
> + memset(&io, 0, sizeof(io)); if (!prw_handle && prw_open (false))
> goto non_atomic; status = NtReadFile (prw_handle, NULL, NULL,
> NULL, &io, buf, count,
your mailer screwed up the patch and so it can't apply. Can you please
send it as an attachment?
Thanks,
Corinna
--
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Maintainer cygwin AT cygwin DOT com
Red Hat
