On Fri, Jul 14, 2023, at 20:34, Ian Rogers wrote:
On Thu, Jun 22, 2023 at 8:10 AM Arnd Bergmann arnd@arndb.de 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/tool...
Caused an issue with building: tools/perf/util/cs-etm.c https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tool...
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