netdev - [PATCH] libbpf: avoid inline hint definition from 'linux/stddef.h'

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Date:   Sun, 14 Mar 2021 18:38:38 +0100
From:   Pedro Tammela <pctammela@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Pedro Tammela <pctammela@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: [PATCH] libbpf: avoid inline hint definition from 'linux/stddef.h'

Linux headers might pull 'linux/stddef.h' which defines
'__always_inline' as the following:

   #ifndef __always_inline
   #define __always_inline __inline__
   #endif

This becomes an issue if the program picks up the 'linux/stddef.h'
definition as the macro now just hints inline to clang.

This change now enforces the proper definition for BPF programs
regardless of the include order.

Signed-off-by: Pedro Tammela <pctammela@...il.com>
---
 tools/lib/bpf/bpf_helpers.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
index ae6c975e0b87..5fa483c0b508 100644
--- a/tools/lib/bpf/bpf_helpers.h
+++ b/tools/lib/bpf/bpf_helpers.h
@@ -29,9 +29,12 @@
  */
 #define SEC(NAME) __attribute__((section(NAME), used))
 
-#ifndef __always_inline
+/*
+ * Avoid 'linux/stddef.h' definition of '__always_inline'.
+ */
+#undef __always_inline
 #define __always_inline inline __attribute__((always_inline))
-#endif
+
 #ifndef __noinline
 #define __noinline __attribute__((noinline))
 #endif
-- 
2.25.1