Hi

like below my app crashes:

float * pin28Value;
*pin28Value = 0.5;
XPLMSetDatavf(pnlBri, pin28Value, 10, 1);

pin28Value needs to be float*. Now I wonder what I'm doing wrong and

how to write the above better and or shorter. The very same but at another

place in my code works!

Thanks in advance

* XPLMSetDatavf
*
* Write part or all of a single precision floating point array dataref. The
* values passed by inValues are written into the dataref starting at
* inOffset. Up to inCount values are written; however if the values would
* write "off the end" of the dataref array, then fewer values are written.
*
* Note: the semantics of array datarefs are entirely implemented by the
* plugin (or X-Plane) that provides the dataref, not the SDK itself; the
* above description is how these datarefs are intended to work, but a rogue
* plugin may have different behavior.
*
*/
XPLM_API void XPLMSetDatavf(
XPLMDataRef inDataRef,
float * inValues,
int inoffset,
int inCount);

You are invoking undefined behavior (you are writing to an uninitialized pointer) and that will either crash or screw up a random part of your program (very bad because it might remain undetected for a very long time and when it starts crashing it will be days to track down the issue).

For this situation the solution would probably be:

float pin28Value = 0.5f;
XPLMSetDatavf(pnlBri, &pin28Value, 10, 1);

Well I tought & to take the address but not the value. Good thanks.

You are invoking undefined behavior (you are writing to an uninitialized pointer) and that will either crash or screw up a random part of your program (very bad because it might remain undetected for a very long time and when it starts crashing it will be days to track down the issue).

For this situation the solution would probably be:

float pin28Value = 0.5f;
XPLMSetDatavf(pnlBri, &pin28Value, 10, 1);

Bitmaster's solution is probably what you are looking for, but I want to show you another way to "solve" your problem, that can give another way of seeing what is happening:

Just want to warn that you should NOT do what I am showing now, but it tells why your code crashed.

This was your code:

float * pin28Value;
*pin28Value = 0.5;
XPLMSetDatavf(pnlBri, pin28Value, 10, 1);

If you just add one line:

float * pin28Value;
pin28Value = malloc(sizeof(float));
*pin28Value = 0.5;
XPLMSetDatavf(pnlBri, pin28Value, 10, 1);

I am not saying this is the way you should solve this problem, because it definitely isn't, but it should give a big hint why your code crashed.