std::system() strange behaviour on Linux Embedded - out-of-memory

Question

I'm struggling with a strange behaviour of the std::system()...
to check the availability of the SysCall I use the following string
int result = system();
(if result is 0 then shell is operative, otherwise not)
I saw that after my process allocates a large ammount of memory the call system() stops working; when process release the memory system() works again.
To check the repeatability of the matter i wrote a very simple program that every 1ms it allocs a new vector bigger than the previous, it checks the system() availability then it deletes the vector (see following code)
unsigned char *dbg_mem = NULL;
tmr_debug.stop();
int sysSts=0;
dbg_mem = new unsigned char[nTmr_debug*1024*1024];
if (dbg_mem==NULL)
{
qDebug("Mem request fails: size =%d MB !!!!!",nTmr_debug);
}
else
{
memset((void*)dbg_mem,0xFF,nTmr_debug*1024*1024);
}
sysSts =system("");
qDebug("Debug Mem: %dMB\t\t result:%d",nTmr_debug, sysSts);
if (dbg_mem)
delete dbg_mem;
if(sysSts!=0)
{
qDebug("****RETRY**** after delete\t result:%d",system(""));
}
nTmr_debug ++;
tmr_debug.start(1);
Sw returns no error untill vector size reaches 72Mb then return -1; if i relase memory works again.:
Debug Mem: 62MB result:0
Debug Mem: 63MB result:0
Debug Mem: 64MB result:0
Debug Mem: 65MB result:0
Debug Mem: 66MB result:0
Debug Mem: 67MB result:0
Debug Mem: 68MB result:0
Debug Mem: 69MB result:0
Debug Mem: 70MB result:0
Debug Mem: 71MB result:-1
****RETRY**** after delete result:0
Debug Mem: 72MB result:-1
****RETRY**** after delete result:0
Debug Mem: 73MB result:-1
****RETRY**** after delete result:0
Debug Mem: 74MB result:-1
****RETRY**** after delete result:0
Debug Mem: 75MB result:-1
****RETRY**** after delete result:0
Debug Mem: 76MB result:-1
As you can see, I still have a lot of memory:
Debug Mem: 135MB result:-1
****RETRY**** after delete result:0
Debug Mem: 136MB result:-1
****RETRY**** after delete result:0
Debug Mem: 137MB result:-1
****RETRY**** after delete result:0
Debug Mem: 138MB result:-1
****RETRY**** after delete result:0
Debug Mem: 139MB result:-1
****RETRY**** after delete result:0
Debug Mem: 140MB result:-1
****RETRY**** after delete result:0
Out of memory: kill process 2127 (MemSizeChek) score 2374 or a child
Killed process 2127 (MemSizeChek)
Killed
cat /proc/meminfo:
MemTotal: 176732 kB
MemFree: 144536 kB
Buffers: 100 kB
Cached: 2440 kB
SwapCached: 0 kB
Active: 328 kB
Inactive: 3096 kB
Active(anon): 64 kB
Inactive(anon): 1044 kB
Active(file): 264 kB
Inactive(file): 2052 kB
Unevictable: 0 kB
Mlocked: 0 kB
SwapTotal: 0 kB
SwapFree: 0 kB
Dirty: 16 kB
Writeback: 0 kB
AnonPages: 912 kB
Mapped: 840 kB
Shmem: 224 kB
Slab: 3208 kB
SReclaimable: 1092 kB
SUnreclaim: 2116 kB
KernelStack: 296 kB
PageTables: 112 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 88364 kB
Committed_AS: 2936 kB
VmallocTotal: 647168 kB
VmallocUsed: 4108 kB
VmallocChunk: 634876 kB
I'm working on a custom board equipped with Linux Kernel 2.6.32 running on ARM TexasDM3730
Toolchain: arm-2009q1-203-arm-none-linux-gnueabi -> gcc version 4.3.3 (Sourcery G++ Lite 2009q1-203)
IDE: Qt Creator 2.5.2
Thanks in advance for any suggestion

Answer 1

I have found the solution: the std::system() call uses inside a fork(). When fork split the main process in 2 processes SO must reserve tha ammount of memory needed for each process. This ammount of memory is not really needed for the child process that call only shell command.
To relsolve I have changed the overcommit memory configuration:
"echo 1 > /proc/sys/vm/overcommit_memory"
and now it works!