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38 lines
1.6 KiB
38 lines
1.6 KiB
commit d26a40412197ba61a72368c71e8a8582d686d28c
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Author: Willy Tarreau <w@1wt.eu>
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Date: Mon Oct 15 11:53:34 2018 +0200
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BUILD: compiler: add a new statement "__unreachable()"
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This statement is used as a hint for the compiler so that it knows that
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the location where it's placed cannot be reached. It will mostly be used
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after longjmp() or equivalent statements that deal with error processing
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and that the compiler doesn't know will not return on certain conditions,
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so that it doesn't complain about null dereferences on error paths.
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(cherry picked from commit 8d26f02e693121764bfa0cb48c9a7ab31e17225d)
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Signed-off-by: Willy Tarreau <w@1wt.eu>
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diff --git a/include/common/compiler.h b/include/common/compiler.h
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index a13aad5c..6f4f5a67 100644
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--- a/include/common/compiler.h
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+++ b/include/common/compiler.h
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@@ -82,6 +82,18 @@
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*/
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#define __maybe_unused __attribute__((unused))
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+/* This allows gcc to know that some locations are never reached, for example
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+ * after a longjmp() in the Lua code, hence that some errors caught by such
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+ * methods cannot propagate further. This is important with gcc versions 6 and
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+ * above which can more aggressively detect null dereferences. The builtin
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+ * below was introduced in gcc 4.5, and before it we didn't care.
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+ */
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+#if __GNUC__ >= 5 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)
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+#define __unreachable() __builtin_unreachable()
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+#else
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+#define __unreachable()
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+#endif
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+
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/*
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* Gcc >= 3 provides the ability for the programme to give hints to the
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* compiler about what branch of an if is most likely to be taken. This
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