03-15-2010
Yes, it will crash because "string" (if this is C) would be a char * allocated on the heap, and if this is c++, is probably the same (but I suppose the C++ STL could implement it any way they wanted). Regardless, it's not going to be compatible with shared memory.
So...as Loic said, you'll have to either live with a predefined size for the entire shared memory segment, or use a separated shared memory management library. It seems even the shared memory management library he supplies, however, is unfortunately not going to be directly compatible with string. Or at least at first blush, it didn't appear to be. It just allows you to dynamically allocate from a shared memory segment (which still must have a fixed size).
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LEARN ABOUT ULTRIX
shmget
shmget(2) System Calls Manual shmget(2)
Name
shmget - get shared memory segment
Syntax
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
int shmget (key, size, shmflg)
key_t key;
int size, shmflg;
Description
The system call returns the shared memory identifier associated with key.
A shared memory identifier and associated data structure and shared memory segment of size size bytes are created for key, if one of the
following is true:
The key is equal to IPC_PRIVATE. For further information, see
The key does not already have a shared memory identifier associated with it, and (shmflg & IPC_CREAT ) is true.
Upon creation, the data structure associated with the new shared memory identifier is initialized as follows:
The and are set equal to the effective user ID and effective group ID of the calling process.
The low-order nine bits of are set equal to the low-order nine bits of shmflg. The is set equal to the value of size.
The and are set equal to zero (0). The shm_ctime is set equal to the current time.
Return Values
Upon successful completion, a non-negative integer, namely, a shared memory identifier is returned. Otherwise, a value of -1 is returned
and errno is set to indicated the error.
Diagnostics
The system call fails if any of the following is true:
[EINVAL] The size is less than the system-imposed minimum or greater than the system-imposed maximum.
[EACCES] A shared memory identifier exists for key, but operations permission, as specified by the low-order nine bits of shmflg,
would not be granted. For further information, see
[EINVAL] A shared memory identifier exists for key, but the size of the segment associated with it is less than size and size is not
equal to zero.
[ENOENT] A shared memory identifier does not exist for key, and (shmflg & IPC_CREAT ) is false.
[ENOSPC] A shared memory identifier is to be created, but the system-imposed limit on the maximum number of allowed shared memory
identifiers would be exceeded.
[ENOMEM] A shared memory identifier and the associated shared memory segment are to be created, but the amount of available physical
memory is not sufficient to fill the request.
[EEXIST] A shared memory identifier exists for key, but ((shmflg & IPC_CREAT ) and (shmflg & IPC_EXCL )) is true.
See Also
shmctl(2), shmop(2), ftok(3)
shmget(2)