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Are the functions "time" and "scandir" thread-safe?

P: n/a
hi,
my multithread application, running under solaris box, is crashing
eventually.
I tried to spot and substitute functions not "thread safe", but I
guess my search wasn't good enough. I have put localtime_r and
asctime_r where I was using localtime and asctime. But I didn't find
any correspondent _r function to "time".Also, I found that "readdir"
is not thread safe. But what about "scandir"?
Thanks for any help
Nov 13 '05 #1
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9 Replies


P: n/a
rn***@yahoo.com (rn***@yahoo.com) wrote in
news:9a**************************@posting.google.c om:
my multithread application, running under solaris box, is crashing
eventually.
I tried to spot and substitute functions not "thread safe",
But C doesn't support threading.
any correspondent _r function to "time".Also, I found that "readdir"
is not thread safe. But what about "scandir"?


I've never seen these functions in C, are you sure you don't need some
other newsgroup that would know about these functions?

--
- Mark ->
--
Nov 13 '05 #2

P: n/a
"Mark A. Odell" <no****@embeddedfw.com> wrote in message news:<Xn********************************@130.133.1 .4>...
rn***@yahoo.com (rn***@yahoo.com) wrote in
news:9a**************************@posting.google.c om:
my multithread application, running under solaris box, is crashing
eventually.
I tried to spot and substitute functions not "thread safe",


But C doesn't support threading.


#include <pthread.h> and link with pthread lib (-lpthread)
Nov 13 '05 #3

P: n/a
rn***@yahoo.com (rn***@yahoo.com) wrote in
news:9a**************************@posting.google.c om:
> my multithread application, running under solaris box, is crashing
> eventually.
> I tried to spot and substitute functions not "thread safe",


But C doesn't support threading.


#include <pthread.h> and link with pthread lib (-lpthread)


That's not an ISO C header though, is it? No, it is not.

--
- Mark ->
--
Nov 13 '05 #4

P: n/a
Though I am probably breaking many "laws" of this newsgroup, I'll answer his
question. Because ISO C doesn't enforce thread safety, your question will
boil
down to your version of the compiler. In most cases, the time function is
not
thread safe.

If you beleive that these functions are not thread safe, whatever thread
support
libraries you are using will have mechanisms to force thread safety on these
functions.
What you will need to do is the following:

1. Create a shared lock on every call to the function in question.
2. Call the function.
3. Immediately copy the data returned from function to another set (Do not
just create
pointer to it, or worse copy the returned pointer).
4. release the lock.

Better yet, create some functions to do the above. This "may" help you
figure out if the
function is thread safe or not. Though not the quickest answer, not the
fastest, nor the least time consuming,
it is however a better answer than being berated for asking a non ISO
question in a newsgroup
whose name is comp.lang.c. It would be nice if the name were changed to
reflect what it is:
comp.lang.c.ISO.||.flame. :)

Michael Steve

"Mark A. Odell" <no****@embeddedfw.com> wrote in message
news:Xn********************************@130.133.1. 4...
rn***@yahoo.com (rn***@yahoo.com) wrote in
news:9a**************************@posting.google.c om:
> my multithread application, running under solaris box, is crashing
> eventually.
> I tried to spot and substitute functions not "thread safe",

But C doesn't support threading.


#include <pthread.h> and link with pthread lib (-lpthread)


That's not an ISO C header though, is it? No, it is not.

--
- Mark ->
--

Nov 13 '05 #5

P: n/a
Michael Steve wrote:
Though I am probably breaking many "laws" of this newsgroup,


Not to mention a few that apply to all of Usenet. Such as "Don't
top-post!". Also, your formatting is all screwy. Are you inserting your
own newlines? Because if so, you are placing them poorly and and your
lines are wrapping anyway, leaving short 1 or 2 word lines.

Besides that, there are good reasons to observe the topicality rules.
Please avoid posting off-topic messages in the future.

-Kevin
--
My email address is valid, but changes periodically.
To contact me please use the address from a recent posting.

Nov 13 '05 #6

P: n/a
On Fri, 05 Dec 2003 00:49:26 GMT, "Michael Steve"
<ms****@columbus.rr.com> wrote:
Though I am probably breaking many "laws" of this newsgroup, I'll answer his
question.


Why? Do you have a personal reason to dislike the other contributors
to this group? Direct the OP to a suitable newsgroup, where he will
surely get a better variety of answers, and where your own answer can
be read, verified, and commented on by people who might know more than
you.

--
Al Balmer
Balmer Consulting
re************************@att.net
Nov 13 '05 #7

P: n/a
"Michael Steve" <ms****@columbus.rr.com> wrote in
news:qC******************@fe3.columbus.rr.com on Thu 04 Dec 2003
05:49:26p:
Though I am probably breaking many "laws" of this newsgroup, I'll
answer his question.


Incorrectly, I might add.

Nov 13 '05 #8

P: n/a
Michael Steve wrote:
Though I am probably breaking many "laws" of this newsgroup, I'll answer his
question.


At one time, I hated comp.lang.c because so many were against off-topic
posts. Despite my disagreeing point-of-view, I continued to read the
messages from this group in hopes of making a better C programmer out of
me. After my C class was over for the semester, I wandered over to an
old Visual Basic newsgroup I once followed, looking to see if any of the
old crew was still around. What I saw shocked me. Messages about Word,
Excel, web development, ADO, etc., etc., etc., plagued the newsgroup. I
estimated for every one on-topic message, there were at least nine
others, which were not. In addition, the same questions were commonly
asked three or four times a day. The number of posts became
overwhelming for people to keep up with. As a result, bad advice was
common place and corrections were rarely made.

Despite the off-topicality and repetitive nature of the messages, no one
seemed to care. Posts were answered and people seemed happy. It was
then that I gained a high level of respect for the people of CLC.
Although seemingly cruel at times, comp.lang.c was by far, the most
professional and informative of all newsgroups I frequently visited.
Messages were clear and quick to the point. Off-topic messages were
redirected to newsgroups possibly containing members more educated in
the topic then anybody here. Furthermore, keeping the amount of noise
down to a low has by far improved my and many others ability to track
down important messages using Google. Above all, if bad or incomplete
advice was given, the people of this newsgroup could be trusted on for
making the necessary corrections.

Has comp.lang.c made a better C programmer out of me? I hope so. If
you absolutely must answer an off-topic message, at least send it in an
email. I personally prefer the redirection for reasons of verification.
I would really hate to see comp.lang.c turn into another newsgroup run
by a bunch of kids. Please don't ruin it for the rest of us by
responding to off-topic posts the way you did.

Sean

Nov 13 '05 #9

P: n/a
rn***@yahoo.com (rn***@yahoo.com) wrote in message news:<9a**************************@posting.google. com>...
"Mark A. Odell" <no****@embeddedfw.com> wrote in message news:<Xn********************************@130.133.1 .4>...
rn***@yahoo.com (rn***@yahoo.com) wrote in
news:9a**************************@posting.google.c om:
my multithread application, running under solaris box, is crashing
eventually.
I tried to spot and substitute functions not "thread safe",


But C doesn't support threading.


#include <pthread.h> and link with pthread lib (-lpthread)


Mark was hinting to you that your message is off-topic for
comp.lang.c, since it talks about libraries and functionality
that are not part of C as such. A good rule of thumb (though
not invariably true) is that if you need to mention a particular
implementation for your question to make sense, then it's
off-topic.

Since you're asking about programming on Solaris, I suggest
comp.unix.programmer or comp.unix.solaris.
Nov 13 '05 #10

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