I copied it wrong ?

[mycuser]

Write your question here.
Hello,
"from a book" this small program does not compile.
I get this error: ISO C++ forbids converting a string constant to ‘char*’
thanks in advance,
Michel Chassey

#include <iostream>

int main()
{
  char * adr;
  adr = "have a good day";
  while( *adr )
    {
     std::cout << *adr;
     adr++;
    }
} // end of main

[whitenite1]

@mycuser

Let us know the actual title and page number of the book your program was copied from, and maybe someone here can find out why it doesn't compile.

[SECMoG1T]

hello there:
yea the string "have a good day"; is of type const char* not type char*

so your code should look like this

#include <iostream>

int main()
{
  const char * adr;
  adr = "have a good day";
  while( *adr )
    {
     std::cout << *adr;
     adr++;
    }
} // end of main 

why the error?

const char* is read-only, meaning you can't modify what is being pointed to, but then you attempt to assign it to a normal char*, which means you *can* modify it... your compiler will never let that happen.

[coder777]

You copy it correctly. I would say that there is a compiler switch which forbids this [wrongful] assignment.

[JLBorges]

> "from a book" this small program does not compile.
> I get this error: ISO C++ forbids converting a string constant to ‘char*’

The book is somewhat dated; the program was made ill-formed by a change to the standard in 2011.

From the C++11 standard (Annex C Compatibility):

Change: String literals made const
The type of a string literal is changed from “array of char” to “array of const char.” ...
The type of a wide string literal is changed from “array of wchar_t” to “array of const wchar_t.”
...
Effect on original feature: Change to semantics of well-defined feature.
Difficulty of converting: Syntactic transformation. The fix is to add a cast
...
How widely used: Programs that have a legitimate reason to treat string literals as pointers to potentially modifiable memory are probably rare.

[mycuser]

Thanks for the speedy answers.
I am reading a french book titled "Programmer en Langage C++" where it says somewhere :
"Achevé d'imprimer le 29 septembre 2017"
This is on page 173.

Topical answer from JLBorges :
From the C++11 standard (Annex C Compatibility):
Change: String literals made const
The type of a string literal is changed from “array of char” to “array of const char.” ...
The type of a wide string literal is changed from “array of wchar_t” to “array of const wchar_t.”

M. JLBorges would you be so kind as to name your reference material as it would most helpful.
I can't understand why a manual published in 2017 would miss the C++11 standard.

Michel Chassey

[JLBorges]

Reference: http://en.cppreference.com/w/
For instance, string literals: http://en.cppreference.com/w/cpp/language/string_literal

C++17 draft standard: http://eel.is/c++draft/

Also see 'Where to get the current standard (C++17)': https://isocpp.org/std/the-standard

[zaphraud]

Yep g++ shows this error too.

Use the C compiler instead of the C++ compiler:

#include <stdio.h>

int main()
{
  char * adr;
  adr = "have a good day";
  while( *adr )
    {
     printf("%c",*adr);
     adr++;
    }
} // end of main 

problem solved.