Question

I want to construct a struct which has an array of unknown number of rows and 2 columns
something like

struct s
{
     cinst char*** s;
}
const char* str1[][2] = {"1","2",
                        "3","4",
                        "5","6"};
s s1 = {str1};
const char* str2[][2] = {"1","2",
                        "3","4"};

s s2 = {str2};

The code fails in compilation.How can I solve the problem?

Answer 1

Aside from the typo cinst and the missing semicolon and assuming (without letting us know) s and struct s are the same type

your problem is that the types of str1 and the struct member s are not compatible

• str1 is of type const char*[][2]
• the struct member is of type const char***

Forcing the compiler to assume str1 is of type const char *** solves your immediate problem, ie, the program compiles and “works”, but you really need to understand that arrays are not pointers and pointers are not arrays. See section 6 of the c-faq site.

struct s
{
     const char*** s;
};
const char* str1[][2] = {"1","2",
                        "3","4",
                        "5","6"};
struct s s1 = {(const char ***)str1};
const char* str2[][2] = {"1","2",
                        "3","4"};

struct s s2 = {(const char ***)str2};