# vtk build error linux release
**URL:** https://discourse.vtk.org/t/vtk-build-error-linux-release/277
**Category:** Support
**Created:** [February 14, 2019, 8:08pm UTC](https://discourse.vtk.org/t/vtk-build-error-linux-release/277 "2019-02-14T20:08:46Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@jal](https://discourse.vtk.org/u/jal)
#### Post date: [February 14, 2019, 8:08pm UTC](https://discourse.vtk.org/t/vtk-build-error-linux-release/277/1 "2019-02-14T20:08:46Z")
Hi, something changed within the past week or so on the vtk master branch, as of today when I build on linux with config RELEASE I get a build failure
/…/VTK/Common/DataModel/vtkSimpleCellTessellator.cxx:2529:5: error: “SLOW\_API” is not defined [-Werror=undef]
#if SLOW\_API
and a similar one in ThirdParty/doubleconversion/vtkdoubleconversion/double-conversion/doubleconversion.cc:532
and they go away if i define CMAKE\_CXX\_FLAGS -Wno-error=undef
Any clue what is causing this behavior?
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### Author:  [@ben.boeckel](https://discourse.vtk.org/u/ben.boeckel)
#### Post date: [February 14, 2019, 8:45pm UTC](https://discourse.vtk.org/t/vtk-build-error-linux-release/277/2 "2019-02-14T20:45:54Z")
Hmm. The dashboards should have caught that. I added `-Werror=undef` recently to try and catch problems. I’ll have an MR up shortly.
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### Author:  [@ben.boeckel](https://discourse.vtk.org/u/ben.boeckel)
#### Post date: [February 14, 2019, 9:01pm UTC](https://discourse.vtk.org/t/vtk-build-error-linux-release/277/3 "2019-02-14T21:01:08Z")
[https://gitlab.kitware.com/vtk/vtk/merge\_requests/5206](https://gitlab.kitware.com/vtk/vtk/merge_requests/5206)
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### Author:  [@jal](https://discourse.vtk.org/u/jal)
#### Post date: [February 15, 2019, 2:14pm UTC](https://discourse.vtk.org/t/vtk-build-error-linux-release/277/4 "2019-02-15T14:14:17Z")
Thanks Ben, is this still waiting on merge request?
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### Author:  [@ben.boeckel](https://discourse.vtk.org/u/ben.boeckel)
#### Post date: [February 15, 2019, 2:23pm UTC](https://discourse.vtk.org/t/vtk-build-error-linux-release/277/5 "2019-02-15T14:23:36Z")
Yes, I got all the instances of the flag causing failures that I hit on my machine on that MR, but there may be code I was not using and have instances still happening. Once that lands, `master` should be much better though.
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### Author:  [@jal](https://discourse.vtk.org/u/jal)
#### Post date: [February 19, 2019, 12:14am UTC](https://discourse.vtk.org/t/vtk-build-error-linux-release/277/6 "2019-02-19T00:14:45Z")
so far just one more
Rendering/OSPRay/vtkOSPRayPass.cxx lines 95 and 105
and vtkOSPRayWindowNode.cxx line 40 something…
and those two fixes gave me a clean build…
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### Author:  [@ben.boeckel](https://discourse.vtk.org/u/ben.boeckel)
#### Post date: [February 19, 2019, 1:27am UTC](https://discourse.vtk.org/t/vtk-build-error-linux-release/277/7 "2019-02-19T01:27:34Z")
@allison.vacanti
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### Author:  [@allison.vacanti](https://discourse.vtk.org/u/allison.vacanti)
#### Post date: [February 19, 2019, 12:14pm UTC](https://discourse.vtk.org/t/vtk-build-error-linux-release/277/8 "2019-02-19T12:14:32Z")
Thanks for letting me know, this should clear that up:
[https://gitlab.kitware.com/vtk/vtk/merge\_requests/5219](https://gitlab.kitware.com/vtk/vtk/merge_requests/5219)