Issue
I'm building on a J1939 project called Open SAE J1939 for industrial Can-bus systems and I notice something with weird with Eclipse CDT.
I call the function
ENUM_J1939_STATUS_CODES SAE_J1939_Send_Request_Address_Claimed(J1939 *j1939, uint8_t DA)
Notice that I'm using uint8_t DA = 0x90 = 144
And why does I get DA = 0xFF = 255 here? Is this a bug in Eclipse CDT 2021-03?
To reproduce this issue. Just download the library and run the Main.c file. This one.
#include "stdlib.h"
#include "stdio.h"
/* Our includes */
#include "Open SAE J1939/Open_SAE_J1939.h"
#include "SAE J1939-71 Application Layer/SAE_J1939-71_Application_Layer.h"
#include "SAE J1939-73 Diagnostics Layer/SAE_J1939-73_Diagnostics_Layer.h"
#include "SAE J1939-81 Network Management Layer/SAE_J1939-81_Network_Management_Layer.h"
#include "ISO 11783 Tractors And Machinery For Agriculture And Forestry/ISO 11783-7 Implement Messages Application Layer/ISO_11783_7_Implement_Messages_Application_Layer.h"
int main() {
/* Create our J1939 structure with two ECU */
J1939 j1939_1;
J1939 j1939_2;
/* Important to set all to 0 */
memset(&j1939_1, 0, sizeof(j1939_1));
memset(&j1939_2, 0, sizeof(j1939_2));
/* Set the ECU address */
j1939_1.this_ECU_address = 0x80; /* From 0 to 253 because 254 = error address and 255 = broadcast address */
j1939_2.this_ECU_address = 0x90;
/* Set NAME for ECU 1 */
j1939_1.this_name.identity_number = 100; /* From 0 to 2097151 */
j1939_1.this_name.manufacturer_code = 300; /* From 0 to 2047 */
j1939_1.this_name.function_instance = 10; /* From 0 to 31 */
j1939_1.this_name.ECU_instance = 2; /* From 0 to 7 */
j1939_1.this_name.function = FUNCTION_VDC_MODULE; /* From 0 to 255 */
j1939_1.this_name.vehicle_system = 100; /* From 0 to 127 */
j1939_1.this_name.arbitrary_address_capable = 0; /* From 0 to 1 */
j1939_1.this_name.industry_group = INDUSTRY_GROUP_CONSTRUCTION; /* From 0 to 7 */
j1939_1.this_name.vehicle_system_instance = 10; /* From 0 to 15 */
/* Set NAME for ECU 2 */
j1939_2.this_name.identity_number = 1000; /* From 0 to 2097151 */
j1939_2.this_name.manufacturer_code = 400; /* From 0 to 2047 */
j1939_2.this_name.function_instance = 20; /* From 0 to 31 */
j1939_2.this_name.ECU_instance = 1; /* From 0 to 7 */
j1939_2.this_name.function = FUNCTION_AUXILIARY_VALVES_CONTROL; /* From 0 to 255 */
j1939_2.this_name.vehicle_system = 50; /* From 0 to 127 */
j1939_2.this_name.arbitrary_address_capable = 0; /* From 0 to 1 */
j1939_2.this_name.industry_group = INDUSTRY_GROUP_AGRICULTURAL_AND_FORESTRY; /* From 0 to 7 */
j1939_2.this_name.vehicle_system_instance = 15; /* From 0 to 15 */
/* Broadcast NAME from ECU 1 */
SAE_J1939_Send_Request_Address_Claimed(&j1939_1, 0x90); /* Request ECU NAME from ECU 2 */
/* Listen for messages at ECU 2 */
Open_SAE_J1939_Listen_For_Messages(&j1939_2);
/* Send NAME from ECU 2 to ECU 1 */
SAE_J1939_Send_Request_Address_Claimed(&j1939_2, 0x80); /* Request ECU NAME from ECU 1 */
/* Listen for messages at ECU 1 */
Open_SAE_J1939_Listen_For_Messages(&j1939_1);
/* Print information */
printf("How many external ECU are connected according to ECU 1? %i\n", j1939_1.number_of_ECU);
printf("How many external ECU are connected according to ECU 2? %i\n", j1939_2.number_of_ECU);
return 0;
}
Solution
Most probably you're a victim of the compiler's optimization. The underlying debugger shows you the contents of some register or memory, but the real value is somewhere else, and it will be arranged if the next call is done. Oh, the call to SAE_J1939_Send_Request() might just be a jump to save clock cycles, because it is the last call and you return its return value.
Please look into the disassembly, and follow the value on that level.
Another option is to reduce the optimization level.
BTW, this has nothing to do with Eclipse. It's a compiler/debugger issue.
Answered By - the busybee
