linux-kernel - [PATCH v3 1/1] libbpf: fix broken gcc SEC pragma macro

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Message-Id: <20220609062412.3950380-1-james.hilliard1@gmail.com>
Date:   Thu,  9 Jun 2022 00:24:12 -0600
From:   James Hilliard <james.hilliard1@...il.com>
To:     bpf@...r.kernel.org
Cc:     James Hilliard <james.hilliard1@...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>,
        netdev@...r.kernel.org (open list:BPF (Safe dynamic programs and tools)),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v3 1/1] libbpf: fix broken gcc SEC pragma macro

It seems the gcc preprocessor breaks unless pragmas are wrapped
individually inside macros when surrounding __attribute__.

Fixes errors like:
error: expected identifier or '(' before '#pragma'
  106 | SEC("cgroup/bind6")
      | ^~~

error: expected '=', ',', ';', 'asm' or '__attribute__' before '#pragma'
  114 | char _license[] SEC("license") = "GPL";
      | ^~~

Signed-off-by: James Hilliard <james.hilliard1@...il.com>
---
Changes v2 -> v3:
  - just fix SEC pragma
Changes v1 -> v2:
  - replace typeof with __typeof__ instead of changing pragma macros
---
 tools/lib/bpf/bpf_helpers.h | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
index fb04eaf367f1..66d23c47c206 100644
--- a/tools/lib/bpf/bpf_helpers.h
+++ b/tools/lib/bpf/bpf_helpers.h
@@ -22,11 +22,12 @@
  * To allow use of SEC() with externs (e.g., for extern .maps declarations),
  * make sure __attribute__((unused)) doesn't trigger compilation warning.
  */
+#define DO_PRAGMA(x) _Pragma(#x)
 #define SEC(name) \
-	_Pragma("GCC diagnostic push")					    \
-	_Pragma("GCC diagnostic ignored \"-Wignored-attributes\"")	    \
+	DO_PRAGMA("GCC diagnostic push")				    \
+	DO_PRAGMA("GCC diagnostic ignored \"-Wignored-attributes\"")	    \
 	__attribute__((section(name), used))				    \
-	_Pragma("GCC diagnostic pop")					    \
+	DO_PRAGMA("GCC diagnostic pop")					    \
 
 /* Avoid 'linux/stddef.h' definition of '__always_inline'. */
 #undef __always_inline
-- 
2.25.1