Re: [Boost-users] why is make_shared using so much of my stack....?

Subject: Re: [Boost-users] why is make_shared using so much of my stack....?
From: Michael Xu (mx2323_at_[hidden])
Date: 2011-02-05 22:00:15

Actually, I put both methods with new and make_shared in there to illustrate
the point.

When I run it JUST with new. It completes. When I run it JUST with
make_shared it fails.

I'm also running on a x86_64 linux machine with 6 gb of ram.

I asked this on the #boost channel on freenode.net, everyone thought I was
confusing stack with heap as well.. but that's not the case... comparing the
stack pointers in each frame using "info register' in gdb tells me that the
space used by the frames in that stack trace are unreasonably large.

On Sat, Feb 5, 2011 at 9:47 PM, Jeff Flinn <TriumphSprint2000_at_[hidden]>wrote:

> Michael Xu wrote:
>
>> Hi everyone,
>>
>> I've been investigating our program's memory usage, and one of the spots
>> that I keep seeing the stack hitting its limit is when using
>> boost::make_shared.
>> I've written a simple test program, that completes fine when I use new...
>> but fails with a stack overflow when I use boost::make_shared
>> ========================
>> #include <iostream>
>> #include <boost/shared_ptr.hpp>
>> #include <boost/make_shared.hpp>
>> using namespace std;
>> struct  arr
>> {
>> char arg[1024*1024];
>> };
>>
>> struct test
>> {
>> struct arr array[1024];
>> };
>>
>> int main()
>> {
>> test * myTest = new test(); //complete! if (!myTest)
>> cout << "new alloc failed";
>> boost::shared_ptr<test> testPtr = boost::make_shared<test>(); //fails with
>> stack overflow!
>> if (!testPtr)
>> {
>> cout << "alloc failed;";
>> }
>> }
>> ===========================
>>
>> If you run this with a reasonable thread stack of 8 megabytes, it fails
>> when using boost::make_shared.
>>
>> Here is the stack trace.....
>> #0  boost::shared_ptr<test>::shared_ptr<test,
>> boost::detail::sp_ms_deleter<test> >(test*,
>> boost::detail::sp_ms_deleter<test>) ()
>> #1  boost::shared_ptr<test> boost::make_shared<test>() ()
>> #2  main ()
>>
>>
>> Is there a reason this happens?
>>
>
> Do you mean heap rather than stack?
>
> You are first allocating with new:
>
> 1024 * 1024 * 1024 = 1,073,741,824 = 1GB of contiguous memory.
>
> Then your attempting to allocate another 1GB with make_shared. This has a
> good chance of failing on 32bit windows systems. You don't mention the OS.
>
> I would expect that make_shared is throwing an exception like
> std::bad_alloc which you are not cathing.
>
> Jeff
>
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-- 
Michael Xu
[phone]
Computer Science
Georgia Tech