Why separate variable definition and initialization in C++?

Question

I\'m currently working on some quite old C++ code and often find things like

int i;
i = 42;

or

Object* someObject = NULL;
someO         


        

Answer 1

There is a good technical reason on ROM-based hardware, it is NOT a style issue:

On ROM/EEPROM based embedded systems, this has an effect on where in the binary the value is written. Uninitialized variables are written into .bss, whereas initialized variables are written into .data. Premature initialization will bloat your ROM space, which on older embedded systems can get you into big, big trouble. If you are running on a system with a small ROM, you can run out of memory if you initialize needlessly. Some goofy compilers will even address directly into the ROM, making these values effectively read-only if you are not careful.

e.g. See this GameBoy example for a more thorough explanation: http://www.nongnu.org/avr-libc/user-manual/FAQ.html#faq_varinit