[Solved] Change constant value [duplicate]

Question

It is certainly undefined behavior, but I am strong proponent of understanding symptoms of undefined behavior for the benefit of spotting one. The results observed can be explained in following manner:

const int a = 5

defined integer constant. Compiler now assumes that value will never be modified for the duration of the whole function, so when it sees

cout<<&a<<" = "<<a;

it doesn’t generate the code to reload the current value of a, instead it just uses the number it was initialized with – it is much faster, than loading from memory.

This is a very common optimization technique – when a certain condition can only happen when the program exhibits undefined behavior, optimizers assume that condition never happens.

Accepted Answer

It is certainly undefined behavior, but I am strong proponent of understanding symptoms of undefined behavior for the benefit of spotting one. The results observed can be explained in following manner:

const int a = 5

defined integer constant. Compiler now assumes that value will never be modified for the duration of the whole function, so when it sees

cout<<&a<<" = "<<a;

it doesn’t generate the code to reload the current value of a, instead it just uses the number it was initialized with – it is much faster, than loading from memory.

This is a very common optimization technique – when a certain condition can only happen when the program exhibits undefined behavior, optimizers assume that condition never happens.