On Wed, Oct 16, 2024 at 11:06:34PM +0100, Lorenzo Stoakes wrote: [sniip]
The import will be fine and you can control that with -I flag in the makefile. Remove these and try to get including linux/pidfd.h working.
I just tried this and it's not fine :) it immediately broke the build as pidfd.h imports linux/fcntl.h which conflicts horribly with system headers on my machine.
For instance f_owner_ex gets redefined among others and fails the build e..g:
/usr/include/asm-generic/fcntl.h:155:8: error: redefinition of ‘struct f_owner_ex’ 155 | struct f_owner_ex { | ^~~~~~~~~~ In file included from /usr/include/bits/fcntl.h:61, from /usr/include/fcntl.h:35, from pidfd_test.c:6: /usr/include/bits/fcntl-linux.h:274:8: note: originally defined here 274 | struct f_owner_ex | ^~~~~~~~~~
It seems only one other test tries to do this as far as I can tell (I only did a quick grep), so it's not at all standard it seems.
This issue occurred even when I used make headers_install to create sanitised user headers and added them to the include path.
A quick google suggests linux/fcntl.h (imported by this pidfd.h uapi header) and system fcntl.h is a known thing. Slightly bizarre...
I tried removing the <fcntl.h> include and that resulted in <sys/mount.h> conflicting:
In file included from /usr/include/fcntl.h:35, from /usr/include/sys/mount.h:24, from pidfd.h:17, from pidfd_test.c:22: /usr/include/bits/fcntl.h:35:8: error: redefinition of ‘struct flock’ 35 | struct flock | ^~~~~ In file included from /tmp/hdr/include/asm/fcntl.h:1, from /tmp/hdr/include/linux/fcntl.h:5, from /tmp/hdr/include/linux/pidfd.h:7, from pidfd.h:6: /usr/include/asm-generic/fcntl.h:195:8: note: originally defined here 195 | struct flock { | ^~~~~
So I don't think I can actually work around this, at least on my system, and I can't really sensibly submit a patch that I can't run on my own machine :)
I may be missing something here.
[snip]
Some added data:
OK so I asked people on fedi to compile the following locally (also a variant with _GNU_SOURCE being defined):
#include <linux/pidfd.h> #include <fcntl.h>
int main(void) {}
And they are all encountering the same issue as I am on a number of different distros (ordering of includes doesn't seem to matter either).
So this seems like a known-broken thing.
And we can't really isolate inclusion of this file since all the tests interact directly with defines from it.
So it seems the only solution is the workaround I suggested previously I think with the header guard define hack.
[snip]