[Qemu-devel] [PATCH 1/5] compiler: add a helper for C99 inline functions

[Paolo Bonzini <pbonzini@redhat.com>]

C99 inline functions are useful whenever a function provide an
abstraction that is generally expected to be inlined away, but
yet a function pointer might be needed.  One such case is function
passed to GCC's cleanup attribute.

Unfortunately, C99 inline functions clash a bit with -Wredundant-decls.
Provide a helper macro to hide the ugliness.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 include/qemu/compiler.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h
index 340e5fdc09..e02b73b9e2 100644
--- a/include/qemu/compiler.h
+++ b/include/qemu/compiler.h
@@ -94,6 +94,21 @@
 #define QEMU_BUILD_BUG_ON_ZERO(x) (sizeof(QEMU_BUILD_BUG_ON_STRUCT(x)) - \
                                    sizeof(QEMU_BUILD_BUG_ON_STRUCT(x)))
 
+/* Provide an extern declaration for a C99 inline function.  This can
+ * be simply placed in a C file but, unfortunately, this means the
+ * declaration comes after the inline definition, and GCC thus
+ * stubbornly raises a -Wredundant-decls warning.
+ *
+ * Putting the declaration before the header would be uglier (it couldn't
+ * just use typeof) and not always possible if the function requires types
+ * that are defined in the header.  Therefore, we just shut up the warning.
+ */
+#define QEMU_EXTERN_INLINE(func)                             \
+    _Pragma("GCC diagnostic push");                          \
+    _Pragma("GCC diagnostic ignored \"-Wredundant-decls\""); \
+    extern typeof(func) func;                                \
+    _Pragma("GCC diagnostic pop")                            \
+
 #if defined __GNUC__
 # if !QEMU_GNUC_PREREQ(4, 4)
    /* gcc versions before 4.4.x don't support gnu_printf, so use printf. */
-- 
2.14.3