# Undefined reference to some SWMR related functions in fortran

**URL:** <https://forum.hdfgroup.org/t/undefined-reference-to-some-swmr-related-functions-in-fortran/13576>\
**Category:** HDF5 Library\
**Created:** [November 5, 2025, 6:37am UTC](https://forum.hdfgroup.org/t/undefined-reference-to-some-swmr-related-functions-in-fortran/13576 "2025-11-05T06:37:19Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![furutaka.kazuyoshi](https://forum.hdfgroup.org/letter_avatar_proxy/v4/letter/f/e5b9ba/32.png) [@furutaka.kazuyoshi](https://forum.hdfgroup.org/u/furutaka.kazuyoshi)\
**Post date:** [November 5, 2025, 6:37am UTC](https://forum.hdfgroup.org/t/undefined-reference-to-some-swmr-related-functions-in-fortran/13576/1 "2025-11-05T06:37:19Z")

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Dear experts,

I’m using a packaged version of HDF5 library for my fortran program on Fedora-43 linux.

When building my program w/ SWMR mode by consulting some guides ([this](https://support.hdfgroup.org/releases/hdf5/documentation/features/SWMR/HDF5_SWMR_Users_Guide.pdf) and [this](https://support.hdfgroup.org/documentation/hdf5-docs/advanced_topics/intro_SWMR.html)) I encountered the following error:

```auto
undefined reference to `h5fstart_swmr_write_f_’

undefined reference to `h5dflush_f_’

```

Indeed, I cannot find fortran interfaces to [h5fstart\_swmr\_write()](https://docs.hdfgroup.org/archive/support/HDF5/doc/RM/RM_H5F.html#File-StartSwmrWrite) and [h5dflush()](https://docs.hdfgroup.org/archive/support/HDF5/doc/RM/RM_H5D.html#Dataset-Flush) in the references.

How can I start the SWMR write and do flush?

What is the proper way to start writing SWMR mode in fortran? Are there any concrete examples?

Thanks in advance…

Kazuyoshi

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<div class="post-metadata">

**Author:** ![furutaka.kazuyoshi](https://forum.hdfgroup.org/letter_avatar_proxy/v4/letter/f/e5b9ba/32.png) [@furutaka.kazuyoshi](https://forum.hdfgroup.org/u/furutaka.kazuyoshi)\
**Post date:** [November 6, 2025, 12:45pm UTC](https://forum.hdfgroup.org/t/undefined-reference-to-some-swmr-related-functions-in-fortran/13576/2 "2025-11-06T12:45:03Z")

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For these, I wrote interface subroutines to call the corresponding functions in C…

I wonder why these essential (I think) routines for SWMR in Fortran don’t exist…

Kazuyoshi

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**Author:** ![brtnfld](https://forum.hdfgroup.org/user_avatar/forum.hdfgroup.org/brtnfld/32/1444_2.png) [@brtnfld](https://forum.hdfgroup.org/u/brtnfld)\
**Post date:** [November 6, 2025, 4:29pm UTC](https://forum.hdfgroup.org/t/undefined-reference-to-some-swmr-related-functions-in-fortran/13576/3 "2025-11-06T16:29:18Z")

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Just an oversight, create a GitHub issue, and I’ll add them.

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<div class="post-metadata">

**Author:** ![furutaka.kazuyoshi](https://forum.hdfgroup.org/letter_avatar_proxy/v4/letter/f/e5b9ba/32.png) [@furutaka.kazuyoshi](https://forum.hdfgroup.org/u/furutaka.kazuyoshi)\
**Post date:** [November 6, 2025, 10:57pm UTC](https://forum.hdfgroup.org/t/undefined-reference-to-some-swmr-related-functions-in-fortran/13576/4 "2025-11-06T22:57:01Z")

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[Just did it](https://github.com/HDFGroup/hdf5/issues/5986).

Thanks in advance…

Kazuyoshi

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<div class="post-metadata">

**Author:** ![furutaka.kazuyoshi](https://forum.hdfgroup.org/letter_avatar_proxy/v4/letter/f/e5b9ba/32.png) [@furutaka.kazuyoshi](https://forum.hdfgroup.org/u/furutaka.kazuyoshi)\
**Post date:** [December 5, 2025, 12:30am UTC](https://forum.hdfgroup.org/t/undefined-reference-to-some-swmr-related-functions-in-fortran/13576/5 "2025-12-05T00:30:56Z")

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Hi…

Will these be in the next patch release, v.2.0.1?

Or we have to wait for [the next minor version update (v.2.1.0)?](https://github.com/HDFGroup/hdf5/milestone/17?closed=1)