On Fri, Jul 14, 2023, at 20:34, Ian Rogers wrote: > On Thu, Jun 22, 2023 at 8:10 AM Arnd Bergmann <arnd@xxxxxxxx> wrote: >> >> On Thu, Jun 22, 2023, at 16:13, Tiezhu Yang wrote: >> > v3: >> > -- Check the definition of __BITS_PER_LONG first at >> > the beginning of uapi/asm-generic/bitsperlong.h >> > > > Thanks for doing this cleanup! I just wanted to report an issue I ran > into with building the Linux perf tool. The header guard in: > tools/include/asm-generic/bitsperlong.h > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/include/asm-generic/bitsperlong.h > > Caused an issue with building: > tools/perf/util/cs-etm.c > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/perf/util/cs-etm.c > > The issue was that cs-etm.c would #include a system header, which > would transitively include a header with the same header guard. This > led to the tools/include/asm-generic/bitsperlong.h being ignored and > the compilation of tools/perf/util/cs-etm.c failing due to a missing > define. My local workaround is: > > ``` > diff --git a/tools/include/asm-generic/bitsperlong.h > b/tools/include/asm-generic/bitsperlong.h > index 2093d56ddd11..88508a35cb45 100644 > --- a/tools/include/asm-generic/bitsperlong.h > +++ b/tools/include/asm-generic/bitsperlong.h > @@ -1,6 +1,6 @@ > /* SPDX-License-Identifier: GPL-2.0 */ > -#ifndef __ASM_GENERIC_BITS_PER_LONG > -#define __ASM_GENERIC_BITS_PER_LONG > +#ifndef __LINUX_TOOLS_ASM_GENERIC_BITS_PER_LONG > +#define __LINUX_TOOLS_ASM_GENERIC_BITS_PER_LONG > #include <uapi/asm-generic/bitsperlong.h> > @@ -21,4 +21,4 @@ > #define small_const_nbits(nbits) \ > (__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG && (nbits) > 0) > -#endif /* __ASM_GENERIC_BITS_PER_LONG */ > +#endif /* __LINUX_TOOLS_ASM_GENERIC_BITS_PER_LONG */ > ``` > > I'm not sure if a wider fix is necessary for this, but I thought it > worthwhile to report that there are potential issues. I don't think we > can use #pragma once, as an alternative to header guards, to avoid > this kind of name collision. Thanks for the report! I think the correct fix is to update the tools/include/ headers to have the same change as the kernel itself. I don't know why we end up including both, that sounds like a separate issue but should normally be harmless as long as the contents are the same. Arnd
