Local variable overwrite global variable

[davideggii]

Hi,
I'm facing a problem in the managing of local variables on STM32WB50CG with the STM32CubeIDE version 1.14.1.
Specifically, the code must perform a write via the sprintf function on a local variable (allocated at address 0x20009bd8).
ALL the writings are performed correctly but during the execution of the same sprintf, a memory area in which a global variable is allocated (address 0x20009708) is also overwritten with the same data without generating any interrupt in MemManage_Handler.

At the end of the execution of DiagnosticPktCreator I obtained the correct string inside the datafifo but the same string is also present at address 0x20009708.

Any ideas on why this occurs?

void DiagnosticPacketGenerator(void){
	char datafifo[MAX_PACKET_SIZE];
	uint16_t fifosize;
	static uint32_t PTimeOld_Diagnostic;
	uint8_t i = 0;
	memset(datafifo,0,MAX_PACKET_SIZE);
	PTimeOld_Diagnostic=(HAL_GetTick()/1000)-PTimeOld_Diagnostic;
	while(i < GetSystemVariable().ValvesNumber)
	{
		/*Diagnostic packet after update (8) or direct reply (0)*/
		if(GetDiagnosticEnable()==3)
			DiagnosticPktCreator(&datafifo[0], &fifosize, 8, PTimeOld_Diagnostic, &i);
		else
			DiagnosticPktCreator(&datafifo[0], &fifosize, 0, PTimeOld_Diagnostic, &i);
		FIFO_Packet_handler_opt(FIFO_PUSH, (uint8_t*)&datafifo[0], &fifosize);
		i++;
	}
	PTimeOld_Diagnostic=(HAL_GetTick())/1000;
}

void DiagnosticPktCreator(char* data, uint16_t* data_size, uint8_t PacketType, uint32_t PTime, uint8_t* idx){
	strcpy(data,"{pkt_9:");
	uint16_t packet_len;

	/*function that adds informations to the packet*/
	Key_DB(&data[strlen(data)],PacketType, PTime);
	Identifying_DB(&data[strlen(data)]);
	Diagnostic_DB(&data[strlen(data)]);
	strcpy(&data[strlen(data)],"}}");
	
	*data_size=strlen(data);
}

void Key_DB(char* data, uint8_t PacketType, uint32_t Time ){	sprintf(data,"{\"key\":\"%u,%s,%lu,%s,%u,%u\"",GetSystemVariable().PacketCounter,GetSystemVariable().Datetime,Time,GetConnection_info().IMEI,GetSystemVariable().Bootcode,PacketType);
}

void Identifying_DB(char* data){
	sprintf(data,",\"id\":\"%s,%s\"",GetConnection_info().ICCID,GetConnection_info().Cell_info);
}

void Diagnostic_DB(char* data){
	sprintf(data,",\"diagnostic\":\"%u,%s,%.f,%u,%s\"",GetSystemVariable().EDStatus,GetConnection_info().Cell_pwr,GetSystem_Acquisition().Voltage,GetSystem_Acquisition().Frequency,FW_VERSION);
}

Thank you in advance.

Davide Graziani

[Andrew Neil]

stack overflow?

buffer overrun?

bad pointers?

You're going to need to show the code!

https://community.st.com/t5/community-guidelines/how-to-write-your-question-to-maximize-your-chances-to-find-a/ta-p/575228

[Tesla DeLorean]

Not entirely sure what you're describing..

The top of the statics, locale, heap and the bottom of the stack can collide.You can perhaps watch the stack size/depth and check heap integrity.

You'd need/want to enable stack checking options, check malloc() returns, and perhaps understand the linked-lists the C libraries are using so you can walk them.

MemManage / HardFault only likely to fire in gross situations, you can do a lot of damage sliently and without warnings.

Perhap add some guard zones and check their integrity periodically.

[davideggii]

Thank you for the advice, it is my first question. I add the code snippet in the question.

Davide Graziani

[davideggii]

Tank you for the reply.

"The top of the statics, locale, heap and the bottom of the stack can collide" If this occurs i think that i will see only one string that overwrites other variables, in this case i obtain the correct value in the correct memory address and also an exact copy of the variable allocated in another memory address. 

"You'd need/want to enable stack checking options, check malloc() returns" I cannot check the malloc() return because i don't use any dynamic allocation.

I add the code in the question if you want to look at it.

Davide Graziani