Question

These are my two structs:

struct upset {
  int location;     
  int trigger;    
  int type;      
  char bits[8]; 
  }; 

struct event {
  int category;
  int spill;
  int num_clock_ups;
  int num_data_ups;
  struct upset clock_ups[512];
  struct upset data_ups[512];
  };

but when i try to declare an array of struct events further down with this:

int nevents = 1755;
struct event total_events[nevents];

i get a segfault the first time i try to access anything in the array, upon checking with gdb, just before the segfault sizeof(total_events) is 0 and the difference in locations of total_events[1] and total_events[2] is 0x10, so it seems the arrays of struct upsets are not getting intialized or something.

what did i do wrong in initializing this array? are my structs set up poorly? i am very new at structs in C and in general.

Answer 1

Is your process stack space big enough? By my calculation that array is going to take up at least (ignoring potential structure member alignment padding):

[2*(13*512) + 4]*1755 = 22.3 MB

of space. If total_events is a local variable, it’ll be allocated on the stack. Do you have that much stack space?