Memory management of NXC strcat

[muntoo]

You should use strlen() instead of the deprecated StrLen(). Same with SubStr().

Try it with:

Code: Select all

arrinit tmp, 0, 1

Where does it freeze? The last block?

[ejvaughan]

You should use strlen() instead of the deprecated StrLen(). Same with SubStr().

Try it with:

Code: Select all

arrinit tmp, 0, 1

Where does it freeze? The last block?

I tried your suggestion, but it still fails at some point during the last block. And the reason I know it has something to do with Mr. Hansen's code is because if I just write the data to a file, everything goes fine. There's something funny going on with that asm block...

[muntoo]

Put CLICK between each line of code in the last block. (Excluding inside the asm block.)

Code: Select all

#define CLICK while(!(ButtonPressed(BTNCENTER, 0))); \
    while(ButtonPressed(BTNCENTER, 0));

Code: Select all

   while(numBytesWritten < size) {
      while(ReceiveMessage(0, true, packet) != LDR_SUCCESS);
CLICK
      asm {
         strcat tmp, message, packet
         mov message, tmp
         arrinit tmp, 0, 0
      }
CLICK
      numBytesWritten += StrLen(packet);
CLICK
   }

How many CLICKs till the program freezes?

-----

If clicks % 3 == 1, then try this program:

Code: Select all

   while(numBytesWritten < size) {
      while(ReceiveMessage(0, true, packet) != LDR_SUCCESS);
      asm { strcat tmp, message, packet } CLICK
      asm { mov message, tmp } CLICK
      asm { arrinit tmp, 0, 0 } CLICK
      numBytesWritten += StrLen(packet);
   }

How many CLICKs this time?

-----

P.S. If clicks > 30, you don't have to keep clicking a few thousand more times. You could then replace the definition with:

Code: Select all

unsigned long clicks = 0;

// CHANGE THESE!!
#define SKIP 30
#define WAIT 500

#define CLICK ++clicks; \
    NumOut(0, 0, clicks, 0); \
    if(clicks >= SKIP) { \
        Wait(WAIT); \
    }

And try it again.

[afanofosc]

Make sure you are using the very latest BricxCC/NBC/NXC version. There was a bug with uninitialized strings that I have fixed recently and that may not be available in any publicly available version at this time. All your strings need to be null terminated or strcat will fail - possibly crashing your NXT. Try initializing your strings to "" before entering the loop and make sure that packet is absolutely guaranteed to be null terminated. It should be if it is a valid message.

John Hansen

[spillerrec]

In the test release from Marts strcat doesn't seem to crash when the string isn't NULL terminated, it appears it just ignores it completely and assumes that it is there at the end. So if there are multiple strings (or it somehow just have extra NULLs) they also end up in the result from strcat.
Does it still behave like this?

[ejvaughan]

Make sure you are using the very latest BricxCC/NBC/NXC version. There was a bug with uninitialized strings that I have fixed recently and that may not be available in any publicly available version at this time. All your strings need to be null terminated or strcat will fail - possibly crashing your NXT. Try initializing your strings to "" before entering the loop and make sure that packet is absolutely guaranteed to be null terminated. It should be if it is a valid message.

John Hansen

Indeed, the problem turned out to be an uninitialized string. My code works fine now. Even with the asm block, though, it still crashes after receiving too much data, so I've just decided to write it to a file. The performance does not suffer too much. However, I have noticed that there is a drastic difference between the performance of the bluetooth on my 2009 MacBook Pro and my PowerMac G4. Does anybody know why this could be? When my MacBook Pro is connected to the NXT, it takes forever to send the data over bluetooth. (It took a minute and a half to send a 20.4 kB file.) The PowerMac sends the data over 4x as fast (21 seconds to send the same file). What could be the cause of such a large performance difference? Is it the bluetooth card in my MacBook that is slowing things down? Or perhaps a setting I can change or a patch I can install?

[afanofosc]

The very latest Fantom drivers for Mac OS X might help you, if you do not already have them installed. LEGO released an update that was intended to help improve support for the new bluetooth hardware used in newer Mac computers.

http://cache.lego.com/upload/contentTem ... 5DA785.zip

This is version 1.13, iirc.

When you say your program still crashed after receiving too much data, are you talking about close to 16kb or something much less than that?

John Hansen

[ejvaughan]

The very latest Fantom drivers for Mac OS X might help you, if you do not already have them installed. LEGO released an update that was intended to help improve support for the new bluetooth hardware used in newer Mac computers.

http://cache.lego.com/upload/contentTem ... 5DA785.zip

This is version 1.13, iirc.

When you say your program still crashed after receiving too much data, are you talking about close to 16kb or something much less than that?

John Hansen

Alas, I already have the latest Fantom drivers for Mac OS X installed. In response to your question, the program crashes after receiving 10.3 kB.