Casting const char* to char* crashes

Question

When I'm trying to cast const char* to char* it crashes:

int myfunc(const char*);
const char * str = "test";
myfunc( (char*)str ) // crash

How can I do that?

Most likely your function modify's the string literal causing Undefined Behavior. The string literal "test" should not be modified. If you do so all bets are off. — Alok Save, Apr 15 '13 at 15:51
Check [this](http://stackoverflow.com/questions/9834067/difference-between-char-and-const-char) — Suvarna Pattayil, Apr 15 '13 at 15:53
possible duplicate of [What is the difference between char a\[\] = "string"; and char \*p = "string";](http://stackoverflow.com/questions/9460260/what-is-the-difference-between-char-a-string-and-char-p-string) — Alok Save, Apr 15 '13 at 15:56

score 4 · Answer 1 · answered Apr 15 '13 at 15:52

What you're doing is undefined behavior.

You're not allowed to change the memory pointed to by str. If you need one you can change, declare it this way instead:

char str[] = "test";

This will create a mutable copy of the string literal "test" for you.

Shafik Yaghmour · Accepted Answer · 2013-10-25T17:20:11.553

Update

Attempting to modify a string literal is undefined behavior. If we look at the draft C++ standard section 2.14.5 String literals paragraph 12 says:

Whether all string literals are distinct (that is, are stored in nonoverlapping objects) is implementation defined. The effect of attempting to modify a string literal is undefined.

Crashing is one of many possible results of undefined behavior it is also possible to have a program that appears to work properly.

Alternatively you can create a automatic array as follows:

char str[] = "test" ;

which will have a copy of the string literal which you can then modify.

Original

If myfunc is modifying a string literal then you have undefined behavior which can easily lead to your program crashing.

Casting const char* to char* crashes

2 Answers2