netdev - [bpf-next v3 07/12] tools headers: Adopt compiletime

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Date:   Mon,  8 Jul 2019 18:31:16 +0200
From:   Krzesimir Nowak <krzesimir@...volk.io>
To:     linux-kernel@...r.kernel.org
Cc:     Alban Crequy <alban@...volk.io>,
        Iago López Galeiras <iago@...volk.io>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Stanislav Fomichev <sdf@...gle.com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, xdp-newbies@...r.kernel.org,
        Krzesimir Nowak <krzesimir@...volk.io>
Subject: [bpf-next v3 07/12] tools headers: Adopt compiletime_assert from kernel sources

This will come in handy to verify that the hardcoded size of the
context data in bpf_test struct is high enough to hold some struct.

Signed-off-by: Krzesimir Nowak <krzesimir@...volk.io>
---
 tools/include/linux/compiler.h | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/tools/include/linux/compiler.h b/tools/include/linux/compiler.h
index 1827c2f973f9..b4e97751000a 100644
--- a/tools/include/linux/compiler.h
+++ b/tools/include/linux/compiler.h
@@ -172,4 +172,32 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
 # define __fallthrough
 #endif
 
+
+#ifdef __OPTIMIZE__
+# define __compiletime_assert(condition, msg, prefix, suffix)		\
+	do {								\
+		extern void prefix ## suffix(void) __compiletime_error(msg); \
+		if (!(condition))					\
+			prefix ## suffix();				\
+	} while (0)
+#else
+# define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0)
+#endif
+
+#define _compiletime_assert(condition, msg, prefix, suffix) \
+	__compiletime_assert(condition, msg, prefix, suffix)
+
+/**
+ * compiletime_assert - break build and emit msg if condition is false
+ * @condition: a compile-time constant condition to check
+ * @msg:       a message to emit if condition is false
+ *
+ * In tradition of POSIX assert, this macro will break the build if the
+ * supplied condition is *false*, emitting the supplied error message if the
+ * compiler has support to do so.
+ */
+#define compiletime_assert(condition, msg) \
+	_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
+
+
 #endif /* _TOOLS_LINUX_COMPILER_H */
-- 
2.20.1