Converting char* memory address to void* and back in C

Question

I'm trying to pass a char*'s memory address as a void* , then to convert the void * memory address back to a string somewhere else. So I have,

char *text               // text="somestring";
void *memadrs=&text;

now I'm trying to convert from the void *memadrs to a new char *.

I apologize if there are other topics concerning this already, but with my searches and confusion regarding pointers/referencing them I could not find anything relevant enough to satisfy this.

Cheers for the help!

edit: Sorry for the confusion folks, the char* isn't a constant.

Answer 1

Given const char* text = "somestring", you really should cast to const void* using const void* memadrs = text. This is because "somestring" is a read-only null-terminated string literal. Note that you don't need to use the address-of operator & since text is already a pointer type.

Using a const void* cast helps the emission of compile-time errors if a subsequent cast to char* is attempted. This is useful since the behaviour behaviour on casting memadrs to a char* and then modifying the memory would be undefined since the original memory is read-only.

A C standard reference to back this up:

[C99: 6.7.3/5]: If an attempt is made to modify an object defined with a const-qualified type through use of an lvalue with non-const-qualified type, the behavior is undefined.

To cast back to a const char*, use (const char*)memadrs.

My switching of char const* to const char* is simply personal taste.