[PATCH 2/3] vec: Silence -Wunused-function warnings on clang

[Simon Marchi <simon dot marchi at ericsson dot com>]

clang has a too aggressive (or broken, depends on how you want to see
it) -Wunused-function warning, which is triggered by the functions
defined by DEF_VEC_* but not used in the current source file.  Normally,
it won't warn about unused static inline functions defined in header
files, because it's expected that a source file won't use all functions
defined in a header file it includes.  However, the DEF_VEC_* macros
define those functions in source files, which leads clang to think that
we should remove those functions.  It is therefore missing a check to
see whether those functions are resulting from macro expansion.  A bug
already exists for that:

  https://bugs.llvm.org//show_bug.cgi?id=22712

It's quite easy to silence this warning in a localized way, that is in
the DEF_VEC_* macros.

gdb/ChangeLog:

	* common/diagnostics.h (DIAGNOSTIC_IGNORE_UNUSED_FUNCTION): New
	macro.
	* common/vec.h: Include diagnostics.h.
	(DEF_VEC_I, DEF_VEC_P, DEF_VEC_O): Ignore -Wunused-function
	warning.
---
 gdb/common/diagnostics.h |  3 +++
 gdb/common/vec.h         | 11 +++++++++++
 2 files changed, 14 insertions(+)

diff --git a/gdb/common/diagnostics.h b/gdb/common/diagnostics.h
index 35bacf2..ee824a3 100644
--- a/gdb/common/diagnostics.h
+++ b/gdb/common/diagnostics.h
@@ -35,9 +35,12 @@
 # define DIAGNOSTIC_IGNORE_SELF_MOVE DIAGNOSTIC_IGNORE ("-Wself-move")
 # define DIAGNOSTIC_IGNORE_DEPRECATED_REGISTER \
   DIAGNOSTIC_IGNORE ("-Wdeprecated-register")
+# define DIAGNOSTIC_IGNORE_UNUSED_FUNCTION \
+  DIAGNOSTIC_IGNORE ("-Wunused-function")
 #else
 # define DIAGNOSTIC_IGNORE_SELF_MOVE
 # define DIAGNOSTIC_IGNORE_DEPRECATED_REGISTER
+# define DIAGNOSTIC_IGNORE_UNUSED_FUNCTION
 #endif
 
 #endif /* COMMON_DIAGNOSTICS_H */
diff --git a/gdb/common/vec.h b/gdb/common/vec.h
index 982f771..0221c88 100644
--- a/gdb/common/vec.h
+++ b/gdb/common/vec.h
@@ -20,6 +20,8 @@
 #if !defined (GDB_VEC_H)
 #define GDB_VEC_H
 
+#include "diagnostics.h"
+
 /* The macros here implement a set of templated vector types and
    associated interfaces.  These templates are implemented with
    macros, as we're not in C++ land.  The interface functions are
@@ -408,6 +410,8 @@ typedef struct VEC(T)							  \
 
 /* Vector of integer-like object.  */
 #define DEF_VEC_I(T)							  \
+DIAGNOSTIC_PUSH 							  \
+DIAGNOSTIC_IGNORE_UNUSED_FUNCTION					  \
 static inline void VEC_OP (T,must_be_integral_type) (void)		  \
 {									  \
   (void)~(T)0;								  \
@@ -416,10 +420,13 @@ static inline void VEC_OP (T,must_be_integral_type) (void)		  \
 VEC_T(T);								  \
 DEF_VEC_FUNC_P(T)							  \
 DEF_VEC_ALLOC_FUNC_I(T)							  \
+DIAGNOSTIC_POP								  \
 struct vec_swallow_trailing_semi
 
 /* Vector of pointer to object.  */
 #define DEF_VEC_P(T)							  \
+DIAGNOSTIC_PUSH 							  \
+DIAGNOSTIC_IGNORE_UNUSED_FUNCTION					  \
 static inline void VEC_OP (T,must_be_pointer_type) (void)		  \
 {									  \
   (void)((T)1 == (void *)1);						  \
@@ -428,13 +435,17 @@ static inline void VEC_OP (T,must_be_pointer_type) (void)		  \
 VEC_T(T);								  \
 DEF_VEC_FUNC_P(T)							  \
 DEF_VEC_ALLOC_FUNC_P(T)							  \
+DIAGNOSTIC_POP								  \
 struct vec_swallow_trailing_semi
 
 /* Vector of object.  */
 #define DEF_VEC_O(T)							  \
+DIAGNOSTIC_PUSH 							  \
+DIAGNOSTIC_IGNORE_UNUSED_FUNCTION					  \
 VEC_T(T);								  \
 DEF_VEC_FUNC_O(T)							  \
 DEF_VEC_ALLOC_FUNC_O(T)							  \
+DIAGNOSTIC_POP								  \
 struct vec_swallow_trailing_semi
 
 /* Avoid offsetof (or its usual C implementation) as it triggers
-- 
2.7.4