[PATCH 1/2] Add QEMU_WARN_UNUSED_RESULT attribute

[Manos Pitsidianakis]

This commit adds QEMU_WARN_UNUSED_RESULT, a macro for the gcc function
attribute `warn_unused_result`. The utility of this attribute is to
ensure functions that return values that need to be inspected are not
ignored by the caller.

Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
---
 include/qemu/compiler.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h
index c797f0d457..7ddbf1f1cf 100644
--- a/include/qemu/compiler.h
+++ b/include/qemu/compiler.h
@@ -212,6 +212,20 @@
 # define QEMU_USED
 #endif
 
+/*
+ * From GCC documentation:
+ *
+ *   The warn_unused_result attribute causes a warning to be emitted if a
+ *   caller of the function with this attribute does not use its return value.
+ *   This is useful for functions where not checking the result is either a
+ *   security problem or always a bug, such as realloc.
+ */
+#if __has_attribute(warn_unused_result)
+# define QEMU_WARN_UNUSED_RESULT __attribute__((warn_unused_result))
+#else
+# define QEMU_WARN_UNUSED_RESULT
+#endif
+
 /*
  * Ugly CPP trick that is like "defined FOO", but also works in C
  * code.  Useful to replace #ifdef with "if" statements; assumes
-- 
2.39.2