String in function parameter

Question

int main             char  x    HelloWorld           char y      HelloWorld            x 0     Z             y 0     M            return 0      In the above program  HelloWorld will be in read-only section i e string table   x will be pointing to that read-only section  so trying to modify that values will be undefined behavior   But y will be allocated in stack and HelloWorld will be copied to that memory  so modifying y will works fine  String literals  pointer vs  char array  Here is my Question    In the following program  both char  arr and char arr   causes segmentation fault if the content is modified    void function char arr      void function char  arr       arr 0     X             int main        function  MyString           return 0       How it differs in the function parameter context  No memory will be allocated for function parameters      Please share your knowledge

User · Answer

char  arr   above statement implies that arr is a character pointer and it can point to either one character or strings of character   amp  char arr    above statement implies that arr is strings of character and can store as many characters as possible or even one but will always count on   0  character hence making it a string    e g  char arr     a  is similar to char arr     a    0      But when used as parameters in called function  the string passed is stored character by character in formal arguments making no difference

User · Answer

Inside the function parameter list  char arr   is absolutely equivalent to char  arr  so the pair of definitions and the pair of declarations are equivalent   void function char arr            void function char  arr            void function char arr     void function char  arr     The issue is the calling context   You provided a string literal to the function  string literals may not be modified  your function attempted to modify the string literal it was given  your program invoked undefined behaviour and crashed   All completely kosher   Treat string literals as if they were static const char literal      string literal   and do not attempt to modify them

User · Answer

function  MyString      is similar to  char  s    MyString   function s      MyString  is in both cases a string literal and in both cases the string is unmodifiable   function  MyString      passes the address of a string literal to function as an argument

[c] String in function parameter

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