# Use association of two ultimate entities

**URL:** <https://fortran-lang.discourse.group/t/use-association-of-two-ultimate-entities/10809>\
**Category:** Help\
**Created:** [March 25, 2026, 2:36pm UTC](https://fortran-lang.discourse.group/t/use-association-of-two-ultimate-entities/10809 "2026-03-25T14:36:35Z")\
**Posts on this page:** 1\
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**Author:** ![themos](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/themos/32/521_2.png) [@themos](https://fortran-lang.discourse.group/u/themos)\
**Post date:** [March 27, 2026, 8:55pm UTC](https://fortran-lang.discourse.group/t/use-association-of-two-ultimate-entities/10809/18 "2026-03-27T20:55:54Z")

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ONLY is your only defence against typos. Without ONLY, and with modules A and B both making FOO accessible, with a nod from the compiler, the poor user will be faced with a strange error message at line 3776 for mentioning FOO.

It is recognised as a Vulnerability of the language, you can google “Fortran vulnerabilities”.

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