# Mender-flash: lseek64 doesn't work with musl **URL:** \ **Category:** General Discussions\ **Tags:** mender-flash, musl\ **Created:** [October 16, 2024, 12:12pm UTC](https://hub.mender.io/t/mender-flash-lseek64-doesnt-work-with-musl/7232 "2024-10-16T12:12:47Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![JohannesSchilling](https://yyz2.discourse-cdn.com/flex036/user_avatar/hub.mender.io/johannesschilling/32/2316_2.png) [@JohannesSchilling](https://hub.mender.io/u/JohannesSchilling)\ **Post date:** [October 16, 2024, 12:12pm UTC](https://hub.mender.io/t/mender-flash-lseek64-doesnt-work-with-musl/7232/1 "2024-10-16T12:12:47Z")
in our environment, we use mender on a musl-based custom linux distro (yocto build). i’ve stumbled across an error when building `mender-flash`, which uses `lseek64` libc calls unavailable in musl. musl doesn’t have any of the foo64 functions, and instead just transitioned everything to be 64 bit (time\_t, off\_t, …) at some point. so now i’ve replaced the `lseek64` calls in libflash/platformfs.cpp with `lseek`, and added that patch in a yocto .bbappend file as `SRC_URI:append:libc-musl = " file://lseek64.patch"`, so it’s applied when building for a musl-based system. now my question is - would patches for this be accepted upstream? - would you prefer a patch on mender-flash to e.g. add a #define to map both lseek64 and lseek to the same thing, or a patch on the yocto layer like i described above? ---
**Author:** ![TheYoctoJester](https://yyz2.discourse-cdn.com/flex036/user_avatar/hub.mender.io/theyoctojester/32/1444_2.png) [@TheYoctoJester](https://hub.mender.io/u/TheYoctoJester)\ **Post date:** [October 17, 2024, 7:55am UTC](https://hub.mender.io/t/mender-flash-lseek64-doesnt-work-with-musl/7232/2 "2024-10-17T07:55:47Z")
Hi @JohannesSchilling, Thanks for sharing this! Good question, any opinions here @lluiscampos @kacf? From my personal point of view, I’d love to see more streamlined `musl` support as I consider it relevant for a lot of use cases. @JohannesSchilling, do you by any chance already have this in a Github fork so you can submit PRs for discussion? Not promising that they will be merged as-is, but it provides a much better code collaboration platform. Greetz, Josef ---
**Author:** ![kacf](https://yyz2.discourse-cdn.com/flex036/user_avatar/hub.mender.io/kacf/32/146_2.png) [@kacf](https://hub.mender.io/u/kacf)\ **Post date:** [October 17, 2024, 8:57am UTC](https://hub.mender.io/t/mender-flash-lseek64-doesnt-work-with-musl/7232/3 "2024-10-17T08:57:43Z")
I did some research and I think we could actually switch to plain variants everywhere, as long as `-D _FILE_OFFSET_BITS=64` is defined by cmake. This causes `off_t` to become 64-bit everywhere, which is what those interfaces use. In addition to Linux, even QNX [supports this](https://www.qnx.com/developers/docs/7.0.0/index.html#com.qnx.doc.neutrino.lib_ref/topic/summary.html), which I don’t think is a deal breaker, since I believe it’s not going to be used there, but it’s nice to know in any case. So my suggestion is: - Add `target_compile_definitions(crossplatform_compiler_flags INTERFACE _FILE_OFFSET_BITS=64)` around [here](https://github.com/mendersoftware/mender-flash/blob/b10998f355af6def3126ae683e11dcc8003265a4/CMakeLists.txt#L34). - Change `lseek64` calls (and any similar calls you find) into plain variants. Thanks! ---
**Author:** ![JohannesSchilling](https://yyz2.discourse-cdn.com/flex036/user_avatar/hub.mender.io/johannesschilling/32/2316_2.png) [@JohannesSchilling](https://hub.mender.io/u/JohannesSchilling)\ **Post date:** [November 4, 2024, 3:03pm UTC](https://hub.mender.io/t/mender-flash-lseek64-doesnt-work-with-musl/7232/4 "2024-11-04T15:03:01Z")
@TheYoctoJester only as a patch file in our internal layer in the internal gitlab so far. @kacf i made a merge request: [use 64bit filesystem offsets/sizes everywhere by JohannesSchilling · Pull Request #18 · mendersoftware/mender-flash · GitHub](https://github.com/mendersoftware/mender-flash/pull/18)