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authorDavid Daney <david.daney@cavium.com>2012-01-11 03:07:25 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2012-01-11 04:30:42 +0400
commit1399ff86f2a2bbacbbe68fa00c5f8c752b344723 (patch)
tree7cfb8e346ff8d750cbf33bb0655603e21e394c37 /include/linux/compiler.h
parent1e16a539ac16e7b3a8c2cee188897d4bdb88e6e8 (diff)
downloadlinux-1399ff86f2a2bbacbbe68fa00c5f8c752b344723.tar.xz
kernel.h: add BUILD_BUG() macro
We can place this in definitions that we expect the compiler to remove by dead code elimination. If this assertion fails, we get a nice error message at build time. The GCC function attribute error("message") was added in version 4.3, so we define a new macro __linktime_error(message) to expand to this for GCC-4.3 and later. This will give us an error diagnostic from the compiler on the line that fails. For other compilers __linktime_error(message) expands to nothing, and we have to be content with a link time error, but at least we will still get a build error. BUILD_BUG() expands to the undefined function __build_bug_failed() and will fail at link time if the compiler ever emits code for it. On GCC-4.3 and later, attribute((error())) is used so that the failure will be noted at compile time instead. Signed-off-by: David Daney <david.daney@cavium.com> Acked-by: David Rientjes <rientjes@google.com> Cc: DM <dm.n9107@gmail.com> Cc: Ralf Baechle <ralf@linux-mips.org> Acked-by: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/compiler.h')
-rw-r--r--include/linux/compiler.h4
1 files changed, 3 insertions, 1 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 320d6c94ff84..4a243546d142 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -293,7 +293,9 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
#ifndef __compiletime_error
# define __compiletime_error(message)
#endif
-
+#ifndef __linktime_error
+# define __linktime_error(message)
+#endif
/*
* Prevent the compiler from merging or refetching accesses. The compiler
* is also forbidden from reordering successive instances of ACCESS_ONCE(),