new Class() always returning NULL

Using Arduino Programming Questions
#1

Hi i have a sketch like this:

  auto ptr = new Command::ServiceChain("test");
  if (ptr == NULL) beep_fail_fatal(); // <== always returning NULL => beep error

why the constructor returning NULL reference?
i’m using attiny 85.
everything works fine, except the new Class() operator.

#2

What is your SRAM usage? The new operator returns zero, if it can not allocate enough memory.

#3

why no exception occured?

yes the memory getting low:

Sketch uses 6104 bytes (74%) of program storage space. Maximum is 8192 bytes.
Global variables use 387 bytes (75%) of dynamic memory, leaving 125 bytes for local variables. Maximum is 512 bytes.
Low memory available, stability problems may occur.

any idea of reducing memory usage?

there are 4 global variable:

Bluetooth bt(/*rxPin*/BT_RX_PIN, /*txPin*/BT_TX_PIN, /*rsPin*/BT_RS_PIN);
Command cmd;
static bool sdebugOK = false;
static void* _this_ = NULL;

each weight 98, 5, 1, 1 bytes.

and there are a lot of function, some lambda function in my sketch.

#4

why no exception occured?

How would you handle an exception?

#5

Should we just ignore this

"Low memory available, stability problems may occur."

and take guesses at what the constructor does?

#6

AWOL:
How would you handle an exception?

In c# just simple: add try{} catch(){} block.
In c++ should be the same.
The Arduino IDE is bit different than c++ visual studio.

BTW the problem solved.
I googled and found that Arduino hates a lot of strings.

My code surrounded by tons of string for debugging purpose.

After I shortening the strings, memory usage drop significantly.

#7

Exceptions are just that; they should not occur. From memory, in C# catching an exception is significantly slower than testing (e.g. when converting text to int). But in C#, optimising for speed is a waste of time so it's not a train smash.

You can use the F() macro to move fixed text to program memory; that will reduce the buirden on RAM.

#8

YunuZ:
In c# just simple: add try{} catch(){} block.
In c++ should be the same.
The Arduino IDE is bit different than c++ visual studio.

The IDE has nothing at all to do with this.

#9

AVR-G++ does not support exceptions.
Handling exceptions essentially requires an operating system or at least a "significant" run time environment, and an AVR typically has neither.

#10