build.rs fails to detect xen headers

[najamelan]

I try to run build.rs xen, but the detection check for the headers fails:

user@qubes-dev ~/c/u/rumprun> printf '#include <stdint.h>\n#include <xen.h>\n' | cc   -I/usr/include/xen  -x c - -c -o /dev/null
In file included from /usr/lib/gcc/x86_64-redhat-linux/7/include/stdint.h:9:0,
                 from <stdin>:1:
/usr/include/stdint.h:310:17: error: missing binary operator before token "("
 #if __GLIBC_USE (IEC_60559_BFP_EXT)
                 ^

This will compile just fine:

printf '#include <stdint.h>\n#include <xen/xen.h>\n' | cc  -x c - -c -o /dev/null

I don't really manage to figure out why adding the -I flag breaks things...?

I found this: https://forums.xilinx.com/t5/Vivado-High-Level-Synthesis-HLS/Testbench-error-with-gcc/td-p/756773
The xen include directory does have a features.h, but don't exactly grasp how they interfere.

---

Fedora 26
Installed Packages
Name         : gcc                                  - Version      : 7.2.1 - Release      : 2.fc26
Name         : xen-devel - Epoch: 2001 - Version      : 4.8.2 - Release      : 11.fc26

user@qubes-dev ~/c/u/rumprun> gcc -xc -E -v -
Using built-in specs.
COLLECT_GCC=gcc
OFFLOAD_TARGET_NAMES=nvptx-none
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-redhat-linux
Configured with: ../configure --enable-bootstrap --enable-languages=c,c++,objc,obj-c++,fortran,ada,go,lto --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-shared --enable-threads=posix --enable-checking=release --enable-multilib --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-gnu-unique-object --enable-linker-build-id --with-gcc-major-version-only --with-linker-hash-style=gnu --enable-plugin --enable-initfini-array --with-isl --enable-libmpx --enable-offload-targets=nvptx-none --without-cuda-driver --enable-gnu-indirect-function --with-tune=generic --with-arch_32=i686 --build=x86_64-redhat-linux
Thread model: posix
gcc version 7.2.1 20170915 (Red Hat 7.2.1-2) (GCC) 
COLLECT_GCC_OPTIONS='-E' '-v' '-mtune=generic' '-march=x86-64'
 /usr/libexec/gcc/x86_64-redhat-linux/7/cc1 -E -quiet -v - -mtune=generic -march=x86-64
ignoring nonexistent directory "/usr/lib/gcc/x86_64-redhat-linux/7/include-fixed"
ignoring nonexistent directory "/usr/lib/gcc/x86_64-redhat-linux/7/../../../../x86_64-redhat-linux/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/lib/gcc/x86_64-redhat-linux/7/include
 /usr/local/include
 /usr/include
End of search list.

[najamelan]

hmm, and once I cheat the script to get the right header location for Xen, I get more compile errors:

/home/user/code/unikernels/rumprun/src-netbsd/sys/rump/kern/lib/libsys_linux/../../../../compat/linux/common/linux_hdio.c:124:6: 
error: this statement may fall through [-Werror=implicit-fallthrough=]
   if (error == 0)
      ^
/home/user/code/unikernels/rumprun/src-netbsd/sys/rump/kern/lib/libsys_linux/../../../../compat/linux/common/linux_hdio.c:126:2: note: here
  case LINUX_HDIO_GETGEO_BIG_RAW:
  ^~~~
--- dependall-/home/user/code/unikernels/rumprun/src-netbsd/sys/rump ---
--- popcount64.d ---

[najamelan]

Actually the implicit-fallthrough seems to be a GCC7 issue. I'll try to fix it.

[najamelan]

Filed an issue at rumpkernel/src-netbsd: rumpkernel/src-netbsd#4