# Compiler support for one-trip do loops

**URL:** <https://fortran-lang.discourse.group/t/compiler-support-for-one-trip-do-loops/10889>\
**Category:** Help\
**Created:** [May 4, 2026, 1:10am UTC](https://fortran-lang.discourse.group/t/compiler-support-for-one-trip-do-loops/10889 "2026-05-04T01:10:34Z")\
**Posts on this page:** 1\
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**Author:** ![ivanpribec](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/ivanpribec/32/3290_2.png) [@ivanpribec](https://fortran-lang.discourse.group/u/ivanpribec)\
**Post date:** [May 4, 2026, 10:35pm UTC](https://fortran-lang.discourse.group/t/compiler-support-for-one-trip-do-loops/10889/14 "2026-05-04T22:35:42Z")

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> [@msz59](#):
>
> Strangely my memory was right to tell me that in the ancient times, namely F66, the control variable became **undefined** if the DO loop exited _naturally_, i.e. when it surpassed the terminal value.

Also mentioned in this post: [Poll: refactoring a chunk of legacy code - #12 by mecej4](https://fortran-lang.discourse.group/t/poll-refactoring-a-chunk-of-legacy-code/2796/12)

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