Data overflow

[thursdays]

I haven't had much luck searching for an answer, maybe a guru here has one.

This is the basic structure of my program:

program main
open(42,file='output.dat')
do while(x)
process a bunch of data
call output_function
end do
close(42)
end program
subroutine output_function
write(42,y) data_set N
end subroutine

The problem: the program writes many many data sets... but then stops. A new file, 'fort.42' is created, and the last data sets are written here - but many intermediate data sets are lost! This problem persists using Absoft fortran, gfortran, and g95.

Why is this, and how do I work around it? Is it simply a matter of writing too much data to a single datafile?

Thank you for your help.

 

[xwb]

Has your data gone out of bounds an started overwriting the stack?

 

[thursdays]

How would I know if my data is overwriting the stack?

This is along the line of what I thought the problem would be, but do you know of any way to detect when my data is or is about to overwrite the stack?

 

[xwb]

Basically if an array goes outside its bounds, it will overwrite the stack or other variables. eg

integer mmm(5)
integer kkk

kkk = 25
mmm(6) = 99
mmm(7) = 1025

At runtime, this may or may not cause a crash. Depending on how the variables are arranged in memory, you might find that kkk is 99 and that the program returns to somewhere else.

 

[thursdays]

Well, for those who are curious...

As embarrassing as it is to disclose, I have discovered the problem.

My program has a subroutine for writing a data file in case I want to continue where the last computation left off. I later decided it would be nice to call the continuation subroutine at regular intervals in the main loop in case of a power failure or some similar catastrophe.

Turns out the continuation subroutine also used write(42,*). Whoops.