[PATCH 2/2] gdb, gdbsupport: use [[nodiscard]] instead of ATTRIBUTE_UNUSED_RESULT

[simon.marchi@polymtl.ca]

From: Simon Marchi <simon.marchi@polymtl.ca>

Since we require C++17, replace the uses of the ATTRIBUTE_UNUSED_RESULT macro
(which expands to __attribute__ ((__warn_unused_result__))) with the
standard [[nodiscard]] attribute, and drop the macro definition from
gdbsupport/common-defs.h.

Change-Id: I6aa0386ce709e8cce81d2a705362bdd4ceccb543
---
 gdb/parser-defs.h        |  2 +-
 gdb/remote.c             |  2 +-
 gdb/stap-probe.c         | 12 +++++-------
 gdbsupport/buildargv.h   |  2 +-
 gdbsupport/common-defs.h |  1 -
 gdbsupport/gdb_ref_ptr.h |  2 +-
 gdbsupport/scoped_fd.h   |  2 +-
 gdbsupport/scoped_mmap.h |  2 +-
 8 files changed, 11 insertions(+), 14 deletions(-)

diff --git a/gdb/parser-defs.h b/gdb/parser-defs.h
index cfa9d9c111da..96355eb3ca4b 100644
--- a/gdb/parser-defs.h
+++ b/gdb/parser-defs.h
@@ -49,7 +49,7 @@ struct expr_builder
 
   /* Resize the allocated expression to the correct size, and return
      it as an expression_up -- passing ownership to the caller.  */
-  ATTRIBUTE_UNUSED_RESULT expression_up release ()
+  [[nodiscard]] expression_up release ()
   {
     return std::move (expout);
   }
diff --git a/gdb/remote.c b/gdb/remote.c
index 43df087b83b3..e6dc3a56e28d 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -13934,7 +13934,7 @@ class scoped_remote_fd
   DISABLE_COPY_AND_ASSIGN (scoped_remote_fd);
 
   /* Release ownership of the file descriptor, and return it.  */
-  ATTRIBUTE_UNUSED_RESULT int release () noexcept
+  [[nodiscard]] int release () noexcept
   {
     int fd = m_fd;
     m_fd = -1;
diff --git a/gdb/stap-probe.c b/gdb/stap-probe.c
index d28cee8168c3..62fc18f7a958 100644
--- a/gdb/stap-probe.c
+++ b/gdb/stap-probe.c
@@ -261,13 +261,11 @@ enum stap_operand_prec
   STAP_OPERAND_PREC_MUL
 };
 
-static expr::operation_up stap_parse_argument_1 (struct stap_parse_info *p,
-						 expr::operation_up &&lhs,
-						 enum stap_operand_prec prec)
-  ATTRIBUTE_UNUSED_RESULT;
+[[nodiscard]] static expr::operation_up stap_parse_argument_1
+  (stap_parse_info *p, expr::operation_up &&lhs, stap_operand_prec prec);
 
-static expr::operation_up stap_parse_argument_conditionally
-     (struct stap_parse_info *p) ATTRIBUTE_UNUSED_RESULT;
+[[nodiscard]] static expr::operation_up stap_parse_argument_conditionally
+  (stap_parse_info *p);
 
 /* Returns true if *S is an operator, false otherwise.  */
 
@@ -1072,7 +1070,7 @@ stap_parse_argument_conditionally (struct stap_parse_info *p)
 /* Helper function for `stap_parse_argument'.  Please, see its comments to
    better understand what this function does.  */
 
-static expr::operation_up ATTRIBUTE_UNUSED_RESULT
+[[nodiscard]] static expr::operation_up
 stap_parse_argument_1 (struct stap_parse_info *p,
 		       expr::operation_up &&lhs_in,
 		       enum stap_operand_prec prec)
diff --git a/gdbsupport/buildargv.h b/gdbsupport/buildargv.h
index 788c1e38730b..6475ee174de5 100644
--- a/gdbsupport/buildargv.h
+++ b/gdbsupport/buildargv.h
@@ -102,7 +102,7 @@ class gdb_argv
   /* Return the underlying array, transferring ownership to the
      caller.  */
 
-  ATTRIBUTE_UNUSED_RESULT char **release ()
+  [[nodiscard]] char **release ()
   {
     char **result = m_argv;
     m_argv = NULL;
diff --git a/gdbsupport/common-defs.h b/gdbsupport/common-defs.h
index 1c0ae0ad9d1b..ca08939676d9 100644
--- a/gdbsupport/common-defs.h
+++ b/gdbsupport/common-defs.h
@@ -202,7 +202,6 @@
 #undef ATTRIBUTE_NONNULL
 #define ATTRIBUTE_NONNULL(m)
 
-#define ATTRIBUTE_UNUSED_RESULT __attribute__ ((__warn_unused_result__))
 #define ATTRIBUTE_USED __attribute__ ((__used__))
 
 #include "libiberty.h"
diff --git a/gdbsupport/gdb_ref_ptr.h b/gdbsupport/gdb_ref_ptr.h
index 757c3f395bab..77aebd82e5d7 100644
--- a/gdbsupport/gdb_ref_ptr.h
+++ b/gdbsupport/gdb_ref_ptr.h
@@ -183,7 +183,7 @@ class ref_ptr
   /* Return this instance's referent, and stop managing this
      reference.  The caller is now responsible for the ownership of
      the reference.  */
-  ATTRIBUTE_UNUSED_RESULT T *release () noexcept
+  [[nodiscard]] T *release () noexcept
   {
     T *result = m_obj;
 
diff --git a/gdbsupport/scoped_fd.h b/gdbsupport/scoped_fd.h
index 08102eda8ce3..03255ea8db7a 100644
--- a/gdbsupport/scoped_fd.h
+++ b/gdbsupport/scoped_fd.h
@@ -56,7 +56,7 @@ class scoped_fd
 
   DISABLE_COPY_AND_ASSIGN (scoped_fd);
 
-  ATTRIBUTE_UNUSED_RESULT int release () noexcept
+  [[nodiscard]] int release () noexcept
   {
     int fd = m_fd;
     m_fd = -1;
diff --git a/gdbsupport/scoped_mmap.h b/gdbsupport/scoped_mmap.h
index 84ad2c38a152..902a1631b2f8 100644
--- a/gdbsupport/scoped_mmap.h
+++ b/gdbsupport/scoped_mmap.h
@@ -52,7 +52,7 @@ class scoped_mmap
 
   DISABLE_COPY_AND_ASSIGN (scoped_mmap);
 
-  ATTRIBUTE_UNUSED_RESULT void *release () noexcept
+  [[nodiscard]] void *release () noexcept
   {
     void *mem = m_mem;
     m_mem = MAP_FAILED;
-- 
2.54.0