Re: libstdc++/7445: poor performance of std::locale::classic() in multi-threaded applications

[Loren James Rittle <rittle@latour.rsch.comm.mot.com>]

The following reply was made to PR libstdc++/7445; it has been noted by GNATS.

From: Loren James Rittle <rittle@latour.rsch.comm.mot.com>
To: bkoz@gcc.gnu.org, gcc-bugs@gcc.gnu.org, gcc-gnats@gcc.gnu.org,
        gcc-prs@gcc.gnu.org, ljrittle@gcc.gnu.org, shurik@sequoiap.com
Cc:  
Subject: Re: libstdc++/7445: poor performance of std::locale::classic() in multi-threaded applications
Date: Thu, 8 Aug 2002 18:58:42 -0500 (CDT)

 OK, I'd be happy to find a performance fix that doesn't make the
 library code subtly less portable when we have a test case.  A
 reference to code already in our test suite would be acceptable.
 
 I just looked at some locale code in our test suite under gdb and then
 constructed the smallest cases that used std::locale::classic() [1]
 and another that did not [2].  Then, I compiled both [1] and [2] with
 and without -static and looked under gdb.  In all four cases,
 std::locale::classic() was called once before main().
 
 [1]
 #include <locale>
 
 int main (void)
 {
   std::locale::classic();
 }
 
 [2]
 #include <locale>
 
 int main (void)
 {
 }
 
 Benjamin (as the "local locale" expert), is it *always* true that
 std::locale::classic() is called at least once during startup before
 control is transferred to main()?  If so (and will always be so), then
 all thread-related locking could be removed IMHO.  In practice, our
 implementation of the Standard C++ library (with optional threading
 support) already supposes that no thread which uses the library
 implementation may have ever been started before main() is invoked.
 If not true, then this change would make a very hard to detect
 threading bug when the assumption changes.
 
 Regards,
 Loren