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

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 #include 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>) () #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