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Minimal example showing the address of a function pointer being incorrect after a system callback
#include <c_types.h>
#include <osapi.h>
#include <user_interface.h>
#include <espconn.h>
#include <mem.h>
#include <gpio.h>
typedef int (* oGetValueCB)();
typedef void (* oSetValueCB)(int, int);
typedef struct {
int type;
oGetValueCB getValCB;
oSetValueCB setValCB;
int args;
} OHandler;
static OHandler *oHandlers;
int ICACHE_FLASH_ATTR oGpioToggleGetCB() {
return 0;
void ICACHE_FLASH_ATTR oGpioToggleSetCB(int value, int gpio) {
void ICACHE_FLASH_ATTR handleTimeout() {
char msg[64];
os_printf("@oHandlers: 0x%8x\n@oGpioToggleGetCB: 0x%8x\n", &oHandlers, &oGpioToggleGetCB);
os_printf("oHandlers[0].getValCB: 0x%8x\n", oHandlers[0].getValCB);
void user_init(void) {
int gpioPin = 12;
OHandler myHandlers[] = {
{0x99, oGpioToggleGetCB, oGpioToggleSetCB, gpioPin},
{ NULL }
oHandlers = (OHandler*)myHandlers;
os_printf("starting timer\n");
LOCAL os_timer_t timer;
os_timer_setfn(&timer, (os_timer_func_t *)handleTimeout, NULL);
os_timer_arm(&timer, 1000, 0);
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morganrallen commented Feb 9, 2016

As you can see, the address goes from something reasonable to complete nonsense.


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morganrallen commented Feb 9, 2016

Thanks to projectgus I have figure out the issue. By moving the declaration of myHandlers outside user_init it persistent after that function exited.

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