On Fri, Jun 28, 2019 at 1:40 AM Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> wrote: > > Multiple people have suggested compile-testing UAPI headers to ensure > they can be really included from user-space. "make headers_check" is > obviously not enough to catch bugs, and we often leak references to > kernel-space definition to user-space. > > Use the new header-test-y syntax to implement it. Please note exported > headers are compile-tested with a completely different set of compiler > flags. The header search path is set to $(objtree)/usr/include since > exported headers should not include unexported ones. > > We use -std=gnu89 for the kernel space since the kernel code highly > depends on GNU extensions. On the other hand, UAPI headers should be > written in more standardized C, so they are compiled with -std=c90. > This will emit errors if C++ style comments, the keyword 'inline', etc. > are used. Please use C style comments (/* ... */), '__inline__', etc. > in UAPI headers. > > There is additional compiler requirement to enable this test because > many of UAPI headers include <stdlib.h>, <sys/ioctl.h>, <sys/time.h>, > etc. directly or indirectly. You cannot use kernel.org pre-built > toolchains [1] since they lack <stdlib.h>. > > I added scripts/cc-system-headers.sh to check the system header > availability, which CONFIG_UAPI_HEADER_TEST depends on. Perhaps, we could use scripts/cc-can-link.sh for this purpose. The intention is slightly different, but a compiler to link user-space programs must provide necessary standard headers. -- Best Regards Masahiro Yamada
