[ovs-dev] Help with error in <linux/types.h> when compiling custom library

[Jordi Palà]

Dear all,

We are testing a custom library that we want to include to
openvswitch. This library uses netlink and the -DCONFIG_LIBNL20
compilation flag.

We can compile the library standalone and it works, but when we add it
to openvswitch the compilation crashes.

The way we add the library to openvswicth is the following:

1) In lib/automake.mk we add:

lib_libopenvswitch_la_CFLAGS=-DCONFIG_LIBNL20

lib_libopenvswitch_la_SOURCES = \
...
lib/my_library.c \
lib/my_library.h

2) However, when compiling we get the following error

In file included from /usr/include/linux/rtnetlink.h:8:0,
                 from /usr/include/netlink/netlink.h:26,
                 from /usr/include/netlink/genl/genl.h:15,
                 from lib/my_library.h:21,
                 from lib/my_library.c:1:
/usr/include/linux/neighbour.h:11:2: error: unknown type name '__s32'

/usr/include/linux/neighbour.h includes /usr/include/linux/types.h who
should be able to find the type __s32. Indeed the chain of includes in
/usr/include/ should be:

neighbour.h -->  <asm/types.h> --> (I assume this translates into
asm-generic/types.h) --> <asm-generic/int-ll64.h> ---> __s32 is
defined here.

What puzzles me is that if we compile the library outside openvswitch
everything works fine, and /usr/include/linux/neighbour.h can find the
type. This is the compilation command that works from outside
openvswitch:

gcc -O2 -g -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs
-fno-strict-aliasing -fno-common -Werror-implicit-function-declaration
-DCONFIG_LIBNL20 -c -o my_library.o my_library.c

Any help is appreciated.

Best Regards

Jordi Pala