Does Fortran have undefined behavior?

by

Yes, it has. It is just called differently. There are many things that you could do and will make your code not standard conforming, for which there is no requirement to for the processor (compiler) to diagnose such non-conformance (of course, many deviations must be diagnosed). Often the situations will be similar to C undefined-behaviour one (like accesing an array out-of-bounds, signed integer overflow,…). We just say that the code is not standard conforming, that means the standard does not prescribe the outcome of such a code. Such code is not covered but the standard and so anything can result if some compiler (processor) does compile it and you do run it.

That is different from processor dependent behaviour, that one is standard and just implementation dependent.

Just searching here at StackOverflow should give you plenty of examples. Like Is passing the same entity to arguments with different intent undefined behavior? How do Fortran and MPI_Reduce deal with integer overflow?

This answer just answers the question asked but does not attempt to list all possible kinds of UB that can happen in Fortran.

More Related Contents:

  1. Fortran running error
  2. Fortran 90 kind parameter
  3. Fortran: integer*4 vs integer(4) vs integer(kind=4)
  4. Is There a Better Double-Precision Assignment in Fortran 90?
  5. Fortran assignment on declaration and SAVE attribute gotcha
  6. changing array dimensions in fortran
  7. Why should I use interfaces?
  8. Sending 2D arrays in Fortran with MPI_Gather
  9. Fortran OpenMP program shows no speedup of CPU_TIME()
  10. Where to put `implicit none` in Fortran
  11. Function has no implicit type
  12. Print to standard output from a function defined in an Fortran module
  13. ‘*’ and ‘/’ not recognized on input by a read statement
  14. Reading data file in Fortran with known number of lines but unknown number of entries in each line
  15. how to write wrapper for ‘allocate’
  16. gfortran does not allow character arrays with varying component lengths
  17. What does “real*8” mean?
  18. What is the purpose of result variables in Fortran?
  19. Function in fortran, passing array in, receiving array out
  20. Reading writing fortran direct access unformatted files with different compilers
  21. Strange label usage for an IF condition in a DO loop [duplicate]
  22. Fortran OpenMP with subroutines and functions
  23. Error: Nonnegative width required in format string at (1)
  24. Fortran intent(inout) versus omitting intent
  25. Fortran array cannot be returned in function: not a DUMMY variable
  26. Is Fortran unable to do the addition between 865398.78 and -865398.78? Why the answer is -0.03?
  27. Passing size as argument VS assuming shape in Fortran procedures
  28. Fortran SAVE statement
  29. MPI_Gather gives seg fault in the most basic code
  30. Confusing double precision real in Fortran

Leave a Comment