If I define a struct like below
typedef struct Coder { float **data; }; For my convenience, I also define a pointer to this struct
typedef Coder *AUTO; and then I have to initial it by calling
AUTO myInstance = new Coder; My problem appear when I call
myInstance->data= NULL; The VC 2010 told me that there was no type specifier. I don't understand what problem is here. Could you please help me?
If you are in C++, just do :
struct Coder { float **data; }; typedef Coder *AUTO; Also you have to be sure that the AUTO declaration is done after the declaration of your struct or you can forward-declare your struct.
Also, it is possible that NULL is undefined.
You can replace it by 0 or just look at the link I just gave you.
Here is a live example.
EDIT : The code you gave us cannot work :
#include <tchar.h> #include <stdlib.h> #include <string.h> #include <math.h> #include <conio.h> #include <iostream> struct Coder { float **data; // 2-D matrix }; typedef Coder *AUTO; AUTO myFeatures = new Coder; myFeatures->data = NULL; // Forbidden int main (){ myFeatures->data = new float *[2]; myFeatures->data[0] = new float [2]; } You can only have declaration in namespace scope, not expression like that.
In §7.3.1/1 of the standard :
namespace-body:
declaration-seqopt
which says the namespace-body can optionally contain only declaration.
This code will work :
// Your includes struct Coder { Coder() : data(NULL) {} // Constructor who initialize data to NULL // via the member-initialization-list float **data; // 2-D matrix }; typedef Coder *AUTO; AUTO myFeatures = new Coder; // Do you want to keep it in global ?? // It's not a really good design int main (){ // You should put your declaration here. // myFeatures->data = NULL; useless now myFeatures->data = new float *[2]; myFeatures->data[0] = new float [2]; } 
myInstance = new Coder; that this is, in fact, C++ (the tag helps as well). And regardless, I don't believe that is the Op's issue.
struct Coder and the typedef for AUTO are even in the same file. Thus the reason for my answer.In C typedef:
typedef int mango; Now your mango represent "int" datatype.
user defined struct syntax:
struct mystruct; use typedef:
typedef struct mystruct newtype; Now newtype represent your struct mystruct.
Your the typedef name is missing,
typedef struct Coder { float **data; }Coder ; 
typedef struct Coder { float **data; }Coder; will be ok.
typedefdoesn't have a name. Also, what's convenient about theAUTOtypedef? It just looks ugly and obfuscating to me.typedefon thestruct, to begin with? And whiletypedefing the pointer is already ugly and obfuscating, giving it a completely unrelated name, and all caps at that?