Fortran assignment on declaration and SAVE attribute gotcha

Question

In fortran 95, if you assign a variable at declaration

integer :: var = 0

it is equivalent to

integer, save :: var = 0

and the variable is therefore preserved after routine execution (is equivalent to static in C speak) and does not get reinitialized when called again. What is the rationale/technical issue behind such (IMHO dangerous) behavior ?

Answer 1

I don't think that there is some rationale behind such behavior.

But as far as I know, Stefano, you used wrong terminology. In your code there is no assignment statement only variable (var) initialization using initialization expression (0).

integer :: var = 0 ! type declaration & initialization

integer :: var ! type declaration
var = 0        ! assignment

So it seems that it was just committee design decision. If we have such expression (with equality sign in type declaration statement) it is initialization not assignment. And initialization takes place only once during program (and not procedures) execution.

However there might be some historical reasons for such decision. Take a look at this thread.

Today such behavior is dangerous because many other widely used languages follows another conventions about initialization/assignment.