What's the behaviour of “” + number and why c++ compile it?

Question

In the code below i successfully compile it but i can\'t understand why for certain values of number the program crash and for other values it\'s not. Could someone explain the

Answer 1

Pointer arithmetic is the culprit.

A const char* is accepted by operator<<, but will not point to a valid memory address in your example.

If you switch on -Wall, you will see a compiler warning about that:

main.cpp: In function 'int main()':
main.cpp:6:59: warning: array subscript 255 is outside array bounds of 'const char [1]' [-Warray-bounds]
    6 |     std::cout<< "Value 1 : " << std::flush << ("" + number) << std::flush << std::endl;
      |                                                           ^
main.cpp:8:59: warning: array subscript 15155 is outside array bounds of 'const char [1]' [-Warray-bounds]
    8 |     std::cout<< "Value 2 : " << std::flush << ("" + number) << std::flush << std::endl;
      |                                                           ^
Value 1 :  q

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