Electronic – C++ AVR microcontroller optimization problem

I'm faced with a weird problem. I'm developing a program for AVR.

• Microcontroller ATtiny85.
• Frequency 1 MHz.
• Programmer pickit2.
• Software for programming avrdude on Linux.
• Compiler avr-g++.
• Optimization -Os (I tested with -O0, it doesn't work too).

This program must enable output pin PB3. But for some reason, it doesn't.

#include <avr/io.h>
#include <avr/interrupt.h>

#define NOINLINE_ENABLED 1

#if NOINLINE_ENABLED == 1
#define NOINLINE __attribute__ ((noinline))
#else
#define NOINLINE
#endif

// Error occurs only if SetLedState method has noinline attribute or function implemented in other .cpp file (also noinline).
// NOINLINE_ENABLED macros enables noinline for this method
void NOINLINE SetLedState(bool state) {
    if (state)
        PORTB |= (1 << PB3);
    else
        PORTB &= ~(1 << PB3);
}

class Test {
public:
    Test(unsigned int a) : a_(a) {}

    void Update() {
        // a_ for some reasons doesn't equal 5, but it's impossible.
        if (this->a_ == 5)
            SetLedState(true);
    }

private:
    // I don't know why, but error doesn't occur if I add first variable, which can never be used
    // unsigned int padding = 0;

    const unsigned int a_;
};

static Test *test;

ISR(TIMER1_OVF_vect) {
    // error occurs when method called from timer interrupt method
    test->Update();
}

[[noreturn]] int main() {
    test = new Test(5);

    DDRB = (1 << PB3);
    PORTB = 0;

    TIMSK = (1 << TOIE1);
    TCCR1 = (1 << CS10);

    sei();

    // no error occurs when method called from this place
    // test->Update();

    while (true);
}

I wrote some comments to explain why it doesn't work. I think the problem is in the optimizer.
Output PB3 doesn't enable if (and):

• Test::Update method calls from timer overflow interrupt.
• a_ class member has offset 2 and more.
• SetLedState is no inlined or implemented in other *.cpp file.

Why?
Thanks in advance!

Edit:
Also, I tried to change the implementation of new C++ operator.
Earlier it called return alloca(size), but now I tried to call return malloc(size). And it worked. Also, this initialization works too:

static Test test_static;
test = &test_static;

Why it doesn't work with alloca? What is the difference with malloc and alloca AVR functions?