-zero and -save

[cjosefy]

Using 8.1.023:

Could someone provide an example where -zero makes a difference in their output? I've been trying to do a sanity check, but I must be off someplace.

Using the following code:

Code:

PROGRAM ZERO_SAVE

WRITE(*,*) IA

END

If I compile WITHOUT -save, I get the output:

0

I guess intrinsic variables that aren't save get initialized to zero?

If I compile with -save, I get the output:

0

This time, the variable IA is statically allocated (verified with nm).

So, is there a short example where you do need to use -zero? I can't seem to get the code to output bad results. When I compile with g77 I get nonsense output which is what I was expecting to get from ifort, since I never compiled with -zero.

Thanks!

[cjosefy]

bump

[Steven_L_Intel1]

It is more likely to affect subroutines, and can depend on optimization choices. My advice is to always explicitly initialize your variables and don't depend on values starting as zero.