Re: Unixware Patch (Was: Re: Beta2 Tag'd and Bundled ...) - Mailing list pgsql-hackers

On Thu, 4 Sep 2003 05:36 am, Bruce Momjian wrote:
> I would like every operating system that supports thread-safety to run
> this program and report back the results.

Okay, here's results from the machines I have access to... I think what you're
going to find is that an awful lot of platforms that do support pthreads do
not necessarily provide thread-safe libc functions.

Is it possible to identify which functions are likely to be called by multiple
threads and create our own mutex-wrapper functions for them? Disabling
thread-safety seems pretty drastic simply because of a lack of getpwuid_r()
or thread-safe getpwuid(). Or do I misunderstand your concerns?

Regards, Philip.

$ uname -a
OSF1 hostname V4.0 1229 alpha
$ ./a.out
Your getpwuid() changes the static memory area between calls
Your strerror() is _not_ thread-safe
Your functions are _not_ all thread-safe

There are older _r functions, but they're deprecated as the non _r are now
thread-safe.

$ uname -a
SunOS hostname 5.6 Generic_105181-05 sun4m sparc SUNW,SPARCstation-4
$ gcc -lpthread -lnsl test.c # this works
$ ./a.out
Your gethostbyname() is _not_ thread-safe
Your getpwuid() is _not_ thread-safe
Your functions are _not_ all thread-safe

getpwduid_r provided
gethostbyname_r not provided

FreeBSD 5.1 (i386)
$ cc -pthread test.c
$ ./a.out
Your gethostbyname() is _not_ thread-safe
Your getpwuid() is _not_ thread-safe
Your functions are _not_ all thread-safe

manpage notes "BUGS    These functions use static data storage; if the data is needed for future    use, it should be
copiedbefore any subsequent calls overwrite it." 

FreeBSD 4.8 (i386)
$ cc -pthread test.c
$ ./a.out
Your gethostbyname() is _not_ thread-safe
Your getpwuid() is _not_ thread-safe
Your functions are _not_ all thread-safe

manpage notes "BUGS    These functions use static data storage; if the data is needed for future    use, it should be
copiedbefore any subsequent calls overwrite it." 

Linux 2.4.18-3 (i686)
$ ./a.out
Your gethostbyname() is _not_ thread-safe
Your getpwuid() is _not_ thread-safe
Your functions are _not_ all thread-safe

manpage notes "The  functions  gethostbyname()  and gethostbyaddr() may return
pointers to static data, which may be over-      written by later calls. Copying the struct hostent does not suffice,
since it contains pointers  -  a  deep      copy is required.

Glibc2 also has reentrant versions gethostbyname_r() and gethostbyname2_r().
These return 0 on success and      nonzero  on  error.  The  result of the call is now stored in the
struct with address ret.  After the call,      *result will be NULL on error or point to the result on success.
Auxiliary data is stored  in  the  buffer      buf  of  length buflen.  (If the buffer is too small, these functions
will return ERANGE.)  No global vari-      able h_errno is modified, but the address of a variable in which  to
store  error  numbers  is  passed  in      h_errnop."