c++/6052: calls to allocator::~allocator made for empty class

[georgeh@aya.yale.edu]

>Number:         6052
>Category:       c++
>Synopsis:       calls to allocator::~allocator made for empty class
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          pessimizes-code
>Submitter-Id:   net
>Arrival-Date:   Mon Mar 25 07:36:00 PST 2002
>Closed-Date:
>Last-Modified:
>Originator:     George Heintzelman <georgeh@aya.yale.edu>
>Release:        gcc-3.0.4
>Organization:
>Environment:
Solaris 2.8
>Description:
In the following code:
#include <string>

int main() {
  for (int i = 0; i < 100000; ++i) {
    std::string foo("Hello world");
  }
}

g++ generates calls to empty std::allocator::~allocator routines,
as well as empty std::string::Alloc_hider::~Alloc_hider routines,
within the loop.
>How-To-Repeat:
compile with g++ -O3
>Fix:
(sort of) I can get rid of the calls by commenting out
  ~allocator() __STL_NOTHROW {}
in the standard header stl_alloc.h. So I considered submitting
this as a library bug (and the library probably ought to be
changed)... but the compiler really ought to be able to figure
this out. It's not the __STL_NOTHROW, either, leaving it as
   ~allocator() {}
also causes the pessimizing behavior.



>Release-Note:
>Audit-Trail:
>Unformatted: