CODEWITHSUNDEEP
arrayssizepascalansistring
testnameC04
testnameC04

Reputation: 23

c language. SetLength, array of structs

type
TS = record
    FN, RN: String;
end;
var 
Sy: array of TS;     
S: ^String;

...

          SetLength(Sy,2);
          begin
            Sy[0].FN:='123';
            Sy[0].RN:='bad';
            Sy[1].FN:='345';
            Sy[1].RN:='000';
          end;


...

S := @(Sy [i].FN);

How to imitate Pascal logic in C language? Next code does not work:

typedef struct
{
       char FN[256];//char FN[] /*isn't allowed by compiler*/
       char RN[256];//char RN[] /*isn't allowed by compiler*/
} TS;
TS Sy[];
main()
{
    Sy=malloc(2*sizeof(TS));
    strcpy(Sy[1].FN,"1234");
}

QUESTION 1

I get compiler error error C2106: '=' : left operand must be l-value. What should I do to imitate Pascal logic in case of SetLength?

QUESTION 2

How to specify a string of unknown size (Ansistrings is Pascal). When I set char FN[]; I get error error C2229: struct '<unnamed-tag>' has an illegal zero-sized array . What should I do to imitate Pascal logic in case of Ansistring?

Upvotes: 0

Views: 650

Answers (1)

Floofy_KH
Floofy_KH

Reputation: 63

Question 1: malloc() returns a void pointer (void*), so I think Sy would need to be a pointer type. The most direct way would be changing TS Sy[] to TS *Sy. Then when using malloc you will need to cast the pointer to a TS pointer, like so: Sy = (TS*)malloc(2*sizeof(TS));

Question 2: As far as I'm aware, the only suitable type that would work would be a c-string. In which case the solution is similar to that in question one, change FN[] and RN[] to *FN and *RN. I'm not very experienced with C however, and that may not be the most efficient way to handle things, especially since then I believe the struct will not take up a contiguous memory space. Another problem with this is you will still need to specify the size of the c-string at some point, but you will be able to do it dynamically, rather than at compile time.

(Edit) As a side note, you should also use free() to free the memory allocated by malloc when you're done with it.

Upvotes: 0

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