C - Initialize a pointer in a struct

Question

I'm working in C on an Arduino. I'm trying to initialize a pointer inside a struct (linked list). It's meant to be a data object so I want to initialize the entire object at once rather than using malloc later in the code.

const int PINS_LEN = 20;

struct Command {
  float toBrightness; //Percent
  float overTime; //Seconds
};
struct CommandNode {
  struct Command command;
  struct CommandNode *next;
};
struct Sequence {
  struct CommandNode commands;
  float startTime;
  float staggerTime;
  int pins[PINS_LEN];
};
struct SequenceNode { //Pattern
  struct Sequence sequence;
  struct SequenceNode *next;
};

struct SequenceNode pattern = {
  .sequence = {
    .commands = {
      .command = {
        .toBrightness = 100,
        .overTime = 1.0
      },
      //-=-=-=THIS IS WHERE IT DIES=-=-=-
      .next = {
        .command = {
          .toBrightness = 50,
          .overTime = 0.5
        },
        .next = NULL
      },
      //-=-=-=-=-=-=-=-=-=-=
    },
    .startTime = 0.0,
    .staggerTime = 1.0,
    .pins = {0, 1, 2, 3, 4, 5}
  },
  .next = NULL
};

You cannot initialize like that... you're trying to initialize a pointer to be equal to a struct. You probably thought you could do that because a similar pattern works for C strings, but it's very specialized there. You're going to need to initialize your pointer to point to a concrete location, probably at runtime rather than compile time. — mah
– mah, Commented Oct 16, 2015 at 19:56

Iłya Bursov · Accepted Answer · 2015-10-16 19:58:15Z

1

as it was said in comments - the main problem that you need pointer, but provide struct, one variant to work around this could be:

struct CommandNode next = {.command = {.toBrightness = 50, .overTime = 0.5}, .next = NULL};
struct SequenceNode pattern = {.sequence = {
        .commands = {
                .command = {.toBrightness = 100, .overTime = 1.0},
                .next = &next},
        .startTime = 0.0,
        .staggerTime = 1.0,
        .pins = {0, 1, 2, 3, 4, 5}
    },
    .next = NULL};

answered Oct 16, 2015 at 19:58

Iłya Bursov

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