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Fleshed out comments a little more, added a specific check for older systems which return -1 instead of bytes read when the read() call is interrupted and errno is EINTR.

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This commit is contained in:
Ward Fisher 2015-07-21 14:08:44 -06:00
parent 7164a99cbc
commit 8bda7fdf67
1 changed files with 17 additions and 2 deletions
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19
libsrc/posixio.c
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@ -315,7 +315,21 @@ px_pgin(ncio *const nciop,
by a signal (see NCF-337,
http://pubs.opengroup.org/onlinepubs/009695399/functions/read.html)
The case where it's a short read is already handled by the function. */
When this happens, nread will (should) be the bytes read, and
errno will be set to EINTR. On older systems nread might be -1.
If this is the case, there's not a whole lot we can do about it
as we can't compute any offsets, so we will attempt to read again.
This *feels* like it could lead to an infinite loop, but it shouldn't
unless the read is being constantly interrupted by a signal, and is
on an older system which returns -1 instead of bytexs read.
The case where it's a short read is already handled by the function
(according to the comment below, at least). */
do {
nread = read(nciop->fd,vp,extent);
} while (nread == -1 && errno == EINTR);
if(nread != (ssize_t)extent) {
status = errno;
if( nread == -1 || (status != EINTR && status != ENOERR))
@ -323,7 +337,8 @@ px_pgin(ncio *const nciop,
/* else it's okay we read less than asked for */
(void) memset((char *)vp + nread, 0, (ssize_t)extent - nread);
}
*nreadp = nread;
*nreadp = nread;
*posp += nread;
return ENOERR;