"__DELETE" of dynamically created struct

Engineering 🇬🇧
audi0615
2021-04-17
2021-04-18

  • audi0615 - 2021-04-17

    Hi.

    I have two sturcts, stMain and stSub.

    stSub is contained in stMain and both structs are dynamically created using __NEW.

    if I delete stMain, is stSub automatically deleted? or Should i delete stSub first and then delete stMain?

    TYPE stMain :
STRUCT
    pstSub: POINTER TO stSub;
END_STRUCT
END_TYPE

TYPE stSub :
STRUCT
    xTest: BOOL;
END_STRUCT
END_TYPE

PROGRAM PLC_PRG
VAR
    pstMain: POINTER TO stMain;
END_VAR

IF pstMain = 0 THEN

    pstMain:=__NEW(stMain);

    IF pstMain.pstSub = 0 THEN
        pstMain.pstSub=__NEW(stSub);
    END_IF

END_IF

IF pstMain <> 0 THEN
    __DELETE(pstMain); //This command also deletes pstSub??
END_IF
     

    Last edit: audi0615 2021-04-17

  • sgronchi - 2021-04-18

    No, it is not deleted.
    But why do you require a struct that has a pointer to struct? Couldn't you just embed stSub in stMain as a member?

     

    • audi0615 - 2021-04-18

      Thank for your reply.
      Actually the stMain has many big sized stSub members (stSub1~stSub1024) and in most cases only 1~2 of them are used depending on user configuration.
      static declaration of sub structs results in more than 500mb memory allocation for them. so this is only for reducing memory usage.

       

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