How do you initialise a dynamic array in C

Question

How do I achieve the dynamic equivalent of this static array initialisation   char c 2            Sets all members to   0     In other words  create a dynamic array with all values initialised to the termination character   char  c   new char length      how do i amend this

User · Accepted Answer

char  c   new char length

User · Answer

C   has no specific feature to do that  However  if you use a std  vector instead of an array  as you probably should do  then you can specify  a value to initialise the vector with   std  vector  lt char gt  v  100  42      creates  a vector of size 100 with all values initialised to 42

User · Answer

Since c  11 we could use list initialization   char  c   new char length       For an aggregate type  then aggregate initialization will be performed  which has the same effect like char c 2

User · Answer

You can t do it in one line easily  You can do   char  c   new char length   memset c  0  length     Or  you can overload the new operator   void  operator new size t size  bool nullify        void  buf   malloc size        if   buf                    Handle this            memset buf    0   size        return buf      Then you will be able to do   char  c   new true  char length     while  char  c   new char length     will maintain the old behavior   Note  if you want all news to zero out what they create  you can do it by using the same above but taking out the bool nullify part    Do note that if you choose the second path you should overload the standard new operator  the one without the bool  and the delete operator too  This is because here you re using malloc    and the standard says that malloc     delete operations are undefined  So you have to overload delete to use free    and the normal new to use malloc     In practice though all implementations use malloc   free   themselves internally  so even if you don t do it most likely you won t run into any problems  except language lawyers yelling at you

User · Answer

The array form of new-expression accepts only one form of initializer  an empty     This  BTW  has the same effect as the empty    in your non-dynamic initialization     The above applies to pre-C  11 language  Starting from C  11 one can use uniform initialization syntax with array new-expressions  char  c   new char length     char  d   new char length    a    b    c

User · Answer

you have to initialize it  by hand     char  c   new char length   for int i   0 i lt length i        c i    0

User · Answer

No internal means  AFAIK  Use this      memset c  0  length

User · Answer

and the implicit comment by many posters    Dont use arrays  use vectors  All of the benefits of arrays with none of the downsides  PLus you get lots of other goodies  If you dont know STL  read  Josuttis The C   standard library and meyers effective STL

User · Answer

Maybe use std  fill n     char  c   new char length   std  fill n c length 0

User · Answer

Two ways   char  c   new char length   std  fill c  c   length  INITIAL VALUE      just this once  since it s char  you could use memset   Or   std  vector lt char gt  c length  INITIAL VALUE     In my second way  the default second parameter is 0 already  so in your case it s unnecessary   std  vector lt char gt  c length      Edit  go vote for Fred s answer  char  c   new char length

[c++] How do you initialise a dynamic array in C++?

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