Go Down

Topic: char to const char (Read 1 time) previous topic - next topic

i'm trying to use a Real Time Clock (RTC) and a dmd. I am resieving that data from the RTC and trying to put in into a variable that the DMD will understand. it only allows const chars and when i try to make one it comes up with an error (uninitalized const 'abc' (that is the name of the variable). how do i fix this error thanks :-)

MichaelMeissner

#1
Jan 03, 2013, 01:38 pm Last Edit: Jan 03, 2013, 01:41 pm by MichaelMeissner Reason: 1
What is the prototype (call signature) of the DMD function you are trying to call?

If it is something like:

Code: [Select]

void do_something (const char *);


you would just pass in a normal array or pointer to a character, and the compiler will automatically convert from char */char [] to const char *.  What a const pointer means in terms of a function prototype, is the compiler can assume that the memory that the pointer points to is not modified in the function.

For example:

Code: [Select]

extern void do_something (const char *);
extern char array[10];

void test (char *p)
{
 do_something (p);
 do_something ("string");
 do_something (array);
}


When you have a const declaration of a scalar or array, you must initialize it at that point, and the compiler is free for instance to put the variable into read-only memory.

Now, going the other way (from a const pointer to normal pointer) is a type error, and you will need a suitable cast.  Even if you do convert the pointer, it is illegal to actually modify what the pointer points to.

Go Up
 


Please enter a valid email to subscribe

Confirm your email address

We need to confirm your email address.
To complete the subscription, please click the link in the email we just sent you.

Thank you for subscribing!

Arduino
via Egeo 16
Torino, 10131
Italy