Question

I want to copy a char to an address where a given char* points to.

it’s in a function which is called by main:

char data = "       ";
myfunction(data, somethingelse);
...

inside the function i have something like

void myfunction(char* data, short somethingelse) {
...
char byte = 0;
inputfilestream.read(&byte, 1);
*data = byte; // here i get the segfault
data++;
...
}

the segfault also comes when i to the copy using strncpy:

strncpy(data, byte, 1);

why is there a segfault? data isn’t const and the address where i actually write to is exactly the same as the one where i allocated the data-array. i’ve tested that multiple times.

thanks in advance.

Answer 1

String literals are readonly. If you want a modifyable string, you must use an array, e.g.:

char data[10];

Or:

char *data = new char[10];

To elaborate a bit more: the type of a string literal is actually const char*. Assigning a string literal to a non-const char* is therefore technically invalid, but most compilers allow it anyway for legacy reasons. Many modern compilers will at least issue a warning when you try to do that.