'DT_CHR' undeclared when compiling print3d

[companje]

When compiling print3d on OSX (without Docker) I get the error below. I think the #define __USE_BSD is not sufficient on OSX to let the #include <dirent.h> define DT_CHR which has the value 2. As a workaround I added #define DT_CHR 2 to ipc_shared.c. That seems to work.

[  9%] Building C object CMakeFiles/ipc_shared.dir/ipc_shared.c.o
/Volumes/OpenWrt/openwrt/build_dir/target-mips_34kc_musl-1.1.14/print3d/ipc_shared.c: In function 'ipc_find_devices':
/Volumes/OpenWrt/openwrt/build_dir/target-mips_34kc_musl-1.1.14/print3d/ipc_shared.c:112:23: error: 'DT_CHR' undeclared (first use in this function)
    if (ent->d_type == DT_CHR && strncmp(ent->d_name, name, strlen(name)) == 0) {
                       ^
/Volumes/OpenWrt/openwrt/build_dir/target-mips_34kc_musl-1.1.14/print3d/ipc_shared.c:112:23: note: each undeclared identifier is reported only once for each function it appears in
make[5]: *** [CMakeFiles/ipc_shared.dir/ipc_shared.c.o] Error 1
make[4]: *** [CMakeFiles/ipc_shared.dir/all] Error 2
make[3]: *** [all] Error 2
make[2]: *** [/Volumes/OpenWrt/openwrt/build_dir/target-mips_34kc_musl-1.1.14/print3d/.built] Error 2
make[2]: Leaving directory `/Volumes/OpenWrt/openwrt/customfeeds/print3d'
make[1]: *** [package/feeds/customfeeds/print3d/compile] Error 2
make[1]: Leaving directory `/Volumes/OpenWrt/openwrt'
make: *** [package/print3d/compile] Error 2

[woutgg]

It looks like you were running a cross-build, with uClibc replaced by musl. The __USE_BSD define is specifically intended for uClibc (see here). A similar trick can be used for musl, for example by defining _BSD_SOURCE, see here.

[companje]

Ah, that makes sense. Thanks Wouter. I'm not sure how I ended up with musl but I guess it's a good choice for they experiment I'm working on. Can you elaborate a bit about the differences and pros and cons?

[woutgg]

Oh I wouldn't know about that. I only learned about its existence because I noticed it in your compilation log instead of the usual uclibc. :)

While I was looking for info though, I did find a comparison table on their website. As far as I can discern linking against musl yields smaller files (e.g. 13kB vs 70kB for a static hello world binary), I could imagine this adding up to a significant amount over all binaries, but I cannot tell for sure of course. Apart from that, it seems to be somewhat faster (no idea if that will be noticeable) and is a bit more feature-rich in general (or rather: more green boxes for musl than for uclibc in the table).

If we can build an image with musl without too much trouble, we could have a quick look at how they compare in practice, just for fun and profit.

[woutgg]

I don't know atm which revision of OpenWRT we are currently building with, but this might explain the unexpected use of musl Rick encountered: http://comments.gmane.org/gmane.comp.embedded.openwrt.devel/32651.

[peteruithoven]

I'm building from this repo: https://github.com/Doodle3D/openwrt-buildroot/blob/master/dockerfile/Dockerfile#L37 Which was last checked out two months ago: https://hub.docker.com/r/doodle3d/openwrt-buildroot-manual/

[woutgg]

I see. Perhaps the choice is fixed in our .config, here. If that is true, Rick probably created a new config when building an image?

[olijf]

@woutgg I did a little test to see about the size difference and noticed some binaries being smaller... I havent tested the current trunk with our wifibox packages but I am planning on doing so to see if we can switch. As MUSL is the norm in the current trunk (and latest stable) I recommend switching to ensure compatibility. BTW rick wanted to build a small package (https://github.com/companje/up3dload) to use the UP3D printer on the wifibox.

On a side note: packages build with MUSL are not compatible with current Wifibox builds as 14.07 uses uClib to build everything you can not install those packages