cJSON can`t parse more than 4 elements - stm32

Question

Trying to use cJSON parser with STM32F103C8T6 and KEIL IDE
The problem is that the parser works pretty well with up to 4 elements of the JSON string, when trying to add the fifth element it gives up.
This code seems to be OK:
#include "cJSON.h"
const char * my_json_string =
"{\"device\":\"16\",\"class\":\"master\",\"call\":\"start\",\"ar1\":\"10\"}";
int main (void){
char * device;
char * cls;
char * call;
char * arg1;
cJSON * root = cJSON_Parse(my_json_string);
if (root == NULL){
printf(cJSON_GetErrorPtr());
return 0;
}
cJSON * dev = cJSON_GetObjectItem(root, "device");
cJSON * cla = cJSON_GetObjectItem(root, "class");
cJSON * cl = cJSON_GetObjectItem(root, "call");
cJSON * ar1 = cJSON_GetObjectItem(root, "ar1");
device = dev->valuestring;
cls = cla->valuestring;
call = cl->valuestring;
arg1 = ar1->valuestring;
printf (device);
printf (cls);
printf (call);
printf (arg1);
}
When I add the fifth pair of key-value to the string
const char * my_json_string =
"{\"device\":\"16\",\"class\":\"master\",\"call\":\"start\",\"ar1\":\"10\",\"ar2\":\"20\"}";
it throws an error pointer
,"ar2":"20"}
The same code, compiled with NetBeans IDE for the desktop works fine.
Here is the RAM map of the STM32, I see no problems here:
Execution Region RW_IRAM1 (Base: 0x20000000, Size: 0x00000ea0, Max: 0x00005000, ABSOLUTE)
Base Addr Size Type Attr Idx E Section Name Object
0x20000000 0x00000014 Data RW 5 .data system_stm32f10x.o
0x20000014 0x00000014 Data RW 18 .data main.o
0x20000028 0x00000008 Data RW 35 .data usart_f10x.o
0x20000030 0x0000000b Data RW 56 .data led_matrix_64x32.o
0x2000003b 0x00000001 PAD
0x2000003c 0x00000004 Data RW 63 .data time_f10x.o
0x20000040 0x00000014 Data RW 155 .data cjson.o
0x20000054 0x00000004 Data RW 357 .data mc_w.l(mvars.o)
0x20000058 0x00000004 Data RW 358 .data mc_w.l(mvars.o)
0x2000005c 0x00000041 Zero RW 34 .bss usart_f10x.o
0x2000009d 0x00000003 PAD
0x200000a0 0x00000800 Zero RW 54 .bss led_matrix_64x32.o
0x200008a0 0x00000200 Zero RW 7 HEAP startup_stm32f10x_md.o
0x20000aa0 0x00000400 Zero RW 6 STACK startup_stm32f10x_md.o

Answer 1

The problem is that 512 kB for the HEAP size was too low.