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    <p>There is difference between constant pointer and pointer to constant. Constant pointer is a pointer (a number - memory address) that cannot be changed - it always point to the same object given via initialization:</p> <pre><code>int * const const_pointer = &amp;some_int_var; // will be always pointing to this var const_pointer = &amp;some_other_var; // illegal - cannot change the pointer *const_pointer = 2; // legal, the pointer is a pointer to non-const </code></pre> <p>Pointer to constant is a pointer whose pointed value cannot be changed:</p> <pre><code>const int * pointer_to_const = &amp;some_int_var; // doesn't have to be always pointing to this var pointer = &amp;some_other_var; // legal, it's not a constant pointer and we can change it *pointer = 2; // illegal, pointed value cannot be changed </code></pre> <p>You can always assign constant to variable i.e. const pointer to non-const pointer (a). You can cast pointer to non-const to a pointer to const (b). But you cannot cast pointer to const to a pointer to non-const (c):</p> <pre><code>int * pointer; int * const const_pointer = &amp;var; const int * pointer_to_const; /* a */ pointer = const_pointer; // OK, no cast (same type) /* b */ pointer_to_const = pointer; // OK, casting 'int*' to 'const int*' /* c */ pointer = pointer_to_const; // Illegal, casting 'const int*' to 'int*' </code></pre> <p><em>[EDIT] Below, this is not standard c++. However, this is common.[/EDIT]<br /></em> String literal</p> <pre><code>"Hello" </code></pre> <p>is converted to constant pointer to const (<code>const char * const</code>):</p> <pre><code>char *pointer = "Hello"; // Illegal, cannot cast 'const char*' to 'char*' char * const const_pointer = "Hello"; // Illegal, cannot cast 'const char*' to 'char*' const char * pointer_to_const = "Hello"; // OK, we can assign a constant to a variable of the same type (and the type is 'const char*') "Hello" = pointer_to_const; // Illegal cannot re-assign a constant </code></pre> <p>In above examples the second is your case. You tried to initialize <strong>pointer-to-non-const</strong> with a <strong>pointer-to-const</strong> when passing string literal as argument of your function. No matter if these pointers are constants or not, it's matter what do they point to.</p> <p>Summary:<br /> 1) If you cast a pointer of some type to a pointer of another type, you cannot cast pointer-to-const to pointer-to-non-const.<br /> 2) If you have constant pointer, the same rules applies as to other constants - you can assign a constant to a variable but you cannot assign a variable to a constant (except initializing it).</p> <p>// EDIT <br /> As GMan pointed out, the C++98 standard (§4.2/2) allows to implicitly cast string literals (which are constant char arrays) to a non-const char pointer. This is because of backward compatibility (in C language there are no constants).</p> <p>Of course such a conversion can lead to mistakes and compilers will violate the rule and show an error. However, GCC in compatibility mode shows only a warning.</p>
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    1. COThis does contain some wrong information, leading to wrong results. A string literal is an [array of const char's](http://stackoverflow.com/questions/3303164/why-isnt-if-maya-maya-true-in-c/3303212#3303212), not a `const char*` (Though, since it's an array, it can decay into such). While it's true such an array cannot typically be implicitly converted to `char*`, string literals have this special conversion. (It's deprecated, and only exists for backwards compatibility.) So all three of your code examples are completely legal.
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    2. COI wrote that "it is converted to a pointer", not "it is a pointer". It is converted to a pointer that points to the array you are saying about. And you are wrong - string literals cannot be implicitly converted to 'char*'. Maybe you are confused with char array initialization.
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    3. CONo, I'm not. §4.2/2: "A string literal (2.13.4) that is not a wide string literal can be converted to an rvalue of type “pointer to char”; a wide string literal can be converted to an rvalue of type “pointer to wchar_t”. In either case, the result is a pointer to the first element of the array. This conversion is considered only when there is an explicit appropriate pointer target type, and not when there is a general need to convert from an lvalue to an rvalue. [Note: this conversion is deprecated. See Annex D. ]" Like I said, all three lines are legal. (Well, you have four now; the first 3.)
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