Initializing struct using designated initializer in embedded C. "Expected an expression"

Question

I am trying to initialize a struct, and assign values to the struct variables.

My struct:

  typedef struct 
  {
    q31_t A0;
    q31_t A1;
    q31_t A2;
    q31_t State[3];
    q31_t Kp;
    q31_t Ki;
    q31_t Kd;
   } arm_pid_instance_q31;

And when I try to declare and initialize the variable I use the designated initializer:

arm_pid_instance_q31 pitch_pid_instance
={
  .A0 = 0,
  .A1 = 0,
  .A2 = 0,
  .State ={0,0,0},
  .Kd = 0, 
  .Ki = 0, 
  .Kp = 0 
 };

I am using Keil µVision4 and the ARM C compiler for an embedded project. When compiling this code, compiler returns Error #29: Expected an expression. The error occurs on every line in the initialization code.

I read that this is the way to go when writing in ANSI C99, but this doesn't work in my case. How to initialize a struct in ANSI C99

I know i can write the "bad" code:

 arm_pid_instance_q31 pitch_pid_instance;
   pitch_pid_instance.A0 = 0; 
   etc...

but...

Any tips?

---

Update: The following code works:

  arm_pid_instance_q31 pitch_pid_instance = {0,0,0,0,0,0,0,0,0};

But again, this isn't a particulary pretty code or way of doing it.

Answer 1

If you're initializing every thing to 0 just use the universal zero initializer (and ignore any spurious warning the compiler gives you). The universal zero initializer is valid C89, C99, C11 (and I believe it was also valid pre-C89).

arm_pid_instance_q31 pitch_pid_instance = {0};
struct somecomplexstruct array[1000] = {0};

... I'm sure you get the point

---

If you want to initialize to values other than 0, and you don't have a C99 compiler, then you need to do it individually, like in your "bad" code.

Or you could separate the parts that need initialization and copy (not initialize) them

struct substruct {
    q31_t Kp;
    q31_t Ki;
    q31_t Kd;
};
struct arm_pid_instance_q31 {
    q31_t A0;
    q31_t A1;
    q31_t A2;
    q31_t State[3];
    struct substruct K;
};

struct substruct tmp = {42, -1, -1000};
struct arm_pid_instance_q31 pitch_pid_instance; /* uninitialized */
memcpy(&pitch_pid_instance.K, &tmp, sizeof tmp); /* copy values */