Re: [Boost-users] [interprocess] Segmentation fault when using std::string in stl::maps in shared memory

Subject: Re: [Boost-users] [interprocess] Segmentation fault when using std::string in stl::maps in shared memory
From: Ravi (lists_ravi_at_[hidden])
Date: 2008-10-20 11:15:36

On Monday 20 October 2008 02:38:05 hamsinv wrote:
> After a few search I found out that we cannot use std::string. Instead we
> should try with interprocess::basic_string. Can anyone guide me through
> this.

The fundamental issue is that objects which allocate memory on the heap cannot 
be used with shared memory. Consider what happens when you use a construct a 
string in shared memory. Upon construction which requires storage (such as 
assigning it an initial value), the string constructor allocates some memory 
on the heap (not in the shared memory segment), which is visible only in the 
constructing process. Using the memory in the other processes tries to access 
those memory locations which results in undefined behavior. In order to 
overcome this problem, you need to use a shared-memory-aware string, such as 
interprocess::basic_string.

Please read the section named "Limitations When Constructing Objects In Mapped 
Regions" in the interprocess manual for more information.

Regards,
Ravi