Initialize reset struct to zero null

Question

struct x       char a 10       char b 20       int i      char  c      char  d 10        I am filling this struct and then using the values  On the next iteration  I want to reset all the fields to 0 or null before I start reusing it    How can I do that  Can I use memset or I have to go through all the members and then do it individually

User · Answer

You can use memset with the size of the struct   struct x x instance  memset   amp x instance  0  sizeof x instance

User · Answer

Define a const static instance of the struct with the initial values and then simply assign this value to your variable whenever you want to reset it   For example   static const struct x EmptyStruct    Here I am relying on static initialization to set my initial values  but you could use a struct initializer if you want different initial values   Then  each time round the loop you can write   myStructVariable   EmptyStruct

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Better than all above is ever to use Standard C specification for struct initialization   struct StructType structVar    0     Here are all bits zero  ever

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struct x myX        memset  amp x  0  sizeof myX

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In C  it is a common idiom to zero out the memory for a struct using memset   struct x myStruct  memset  amp myStruct  0  sizeof myStruct      Technically speaking  I don t believe that this is portable because it assumes that the NULL pointer on a machine is represented by the integer value 0  but it s used widely because on most machines this is the case   If you move from C to C    be careful not to use this technique on every object   C   only makes this legal on objects with no member functions and no inheritance

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I believe you can just assign the empty set      to your variable   struct x instance   for i   0  i  lt  n  i          instance              Do Calculations

User · Answer

The way to do such a thing when you have modern C  C99  is to use a compound literal   a    const struct x   0      This is somewhat similar to David s solution  only that you don t have to worry to declare an the empty structure or whether to declare it static  If you use the const as I did  the compiler is free to allocate the compound literal statically in read-only storage if appropriate

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Take a surprise from gnu11  typedef struct       uint8 t messType      uint8 t ax     axis     uint32 t position      uint32 t velocity   TgotoData   TgotoData tmpData     0     nothing is zero

User · Answer

If you have a C99 compliant compiler  you can use  mystruct    struct x  0     otherwise you should do what David Heffernan wrote  i e  declare   struct x empty    0     And in the loop   mystruct   empty

[c] Initialize/reset struct to zero/null

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