How to convert const char to char in C

Question

In my project there is a method which only returns a const char   whereas I need a char  string  as the API doesn t accept const char    Any idea how to convert between const char  to char

User · Answer

You can cast it by doing  char   Identifier Of Const char  But as there is probabbly a reason that the api doesn t accept const cahr    you should do this only  if you are sure  the function doesn t try to assign any value in range of your const char  which you casted to a non const one

User · Answer

To convert a const char  to char  you could create a function like this    include  lt stdio h gt   include  lt string h gt   include  lt stdlib h gt   char  unconstchar const char  s        if  s        return NULL      int i      char  res   NULL      res    char   malloc strlen s  1       if  res           fprintf stderr   quot Memory Allocation Failed  Exiting    n quot            exit EXIT FAILURE         else          for  i   0  s i       0   i                  res i    s i                     res i      0           return res           int main         const char  s    quot this is bikash quot       char  p   unconstchar s       printf  quot  s quot  p       free p

User · Answer

You can use the strdup function which has the following prototype   char  strdup const char  s1     Example of use    include  lt string h gt   char   my str   strdup  My string literal     char   my other str   strdup some const str     or strcpy strncpy to your buffer  or rewrite your functions to use const char   as parameter instead of char   where possible so you can preserve the const

User · Answer

A const to a pointer indicates a  read-only  memory location  Whereas the ones without const are a read-write memory areas  So  you  cannot  convert a const read-only location  to a normal read-write  location    The alternate is to copy the data to a different read-write location and pass this pointer to the required function  You may use strdup   to perform this action

User · Answer

First of all you should do such things only if it is really necessary - e g  to use some old-style API with char  arguments which are not modified  If an API function modifies the string which was const originally  then this is unspecified behaviour  very likely crash   Use cast    char  const char ptr

User · Answer

To be safe you don t break stuff  for example when these strings are changed in your code or further up   or crash you program  in case the returned string was literal for example like  quot hello I m a literal string quot  and you start to edit it   make a copy of the returned string  You could use strdup   for this  but read the small print  Or you can of course create your own version if it s not there on your platform

[c] How to convert const char* to char* in C?

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