Request for review: 6749267: Signal handler should save/restore errno

[serguei.spitsyn at oracle.com]

Harold,

Thanks for checking this.
I forgot that the perror() message always matches the latest errno.

Thanks,
Serguei


On 2/18/13 12:29 PM, harold seigel wrote:
> Hi Serguei,
>
> Thanks for reviewing this!
>
> I think that the perror() message will also be preserved.  I tried 
> this with a small C++ program:
>
>     #include <stdio.h>
>     #include <errno.h>
>     #include <sys/stat.h>
>     #include <fcntl.h>
>     #include <unistd.h>
>
>     int main(int argc, char * argv[]) {
>       char buf[20];
>       int old_errno;
>       int bad_fd = 23;
>       int res = open("/i/dont/exist", O_RDONLY);
>       old_errno = errno;
>       perror("errno: ");
>
>       res = read(bad_fd, buf, 10);
>       perror("errno: ");
>
>       errno = old_errno;
>       perror("errno: ");
>       return 0;
>     }
>
> When I ran this program, I got the following result:
>
>     % ./a.out
>     errno: : No such file or directory
>     errno: : Bad file descriptor
>     errno: : No such file or directory
>
> Hopefully, our code will behave the same way.
>
> Thanks, Harold
>
> On 2/18/2013 3:10 PM, serguei.spitsyn at oracle.com wrote:
>> Looks good.
>>
>> I'm not sure it is an ultimate solution though.
>> The error message that is reported by the perror() might be lost as 
>> well,
>> but I'm not sure yet if it is possible to restore it as well.
>>
>> A link:
>> http://www.kernel.org/doc/man-pages/online/pages/man3/perror.3.html
>>
>>
>> Thanks,
>> Serguei
>>
>>
>>
>> On 2/18/13 6:07 AM, harold seigel wrote:
>>> Hi,
>>>
>>> Please review the following change.
>>>
>>> Summary: With this change, the actual signal handler saves the errno 
>>> before calling the function that does most of the signal handling 
>>> processing.  It then restores the value of errno when the signal 
>>> handling processing function returns.
>>>
>>> Open webrev: http://cr.openjdk.java.net/~hseigel/bug_6749267/ 
>>> <http://cr.openjdk.java.net/%7Ehseigel/bug_6749267/>
>>>
>>> Bug link at: https://jbs.oracle.com/bugs/browse/JDK-6749267
>>>
>>> The changes were tested with JPRT, JCK Lang and VM tests, UTE tests, 
>>> and with JPRT.  Also, I used the debugger to change the value of 
>>> errno inside of the signal handling processing method and then 
>>> verified that it got restored properly.
>>>
>>> Thanks!  Harold
>>
>

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