From: Simon Marchi <simon.marchi@efficios.com>
Date: Thu, 4 Aug 2022 18:28:25 +0000 (-0400)
Subject: Silence -Wunused-but-set-variable error with clang
X-Git-Url: https://git.efficios.com/?p=babeltrace.git;a=commitdiff_plain;h=2ea09241f07f1dfd4b6fd0f2f296a10142fda7d2

Silence -Wunused-but-set-variable error with clang

When building with clang-15, I get:

      CXX      libctf_parser_la-parser.lo
    parser.cpp:2920:9: error: variable 'yynerrs' set but not used [-Werror,-Wunused-but-set-variable]
        int yynerrs;
            ^

This is because it warns for something like this:

    int n;
    n = 0;
    ++n;

whereas previous versions do not.

This is generated code, so there's not much more we can do other than
silence the warning for the file.

Change-Id: If2cffe9042b743ffe4b4b23f751216f67b58e5fa
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/8655
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>
---

diff --git a/src/common/macros.h b/src/common/macros.h
index 34ac393f..6a3e061d 100644
--- a/src/common/macros.h
+++ b/src/common/macros.h
@@ -81,6 +81,17 @@ extern "C" {
 	((void) sizeof((void) (_expr1), (void) (_expr2),		\
 		(void) (_expr3), (void) (_expr4), (void) (_expr5), 0))
 
+#if defined __clang__
+#  if __has_warning("-Wunused-but-set-variable")
+#    define BT_DIAG_IGNORE_UNUSED_BUT_SET_VARIABLE \
+	_Pragma("GCC diagnostic ignored \"-Wunused-but-set-variable\"")
+#  endif
+#endif
+
+#if !defined BT_DIAG_IGNORE_UNUSED_BUT_SET_VARIABLE
+#  define BT_DIAG_IGNORE_UNUSED_BUT_SET_VARIABLE
+#endif
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/plugins/ctf/common/metadata/parser.ypp b/src/plugins/ctf/common/metadata/parser.ypp
index b644b5d1..e475436e 100644
--- a/src/plugins/ctf/common/metadata/parser.ypp
+++ b/src/plugins/ctf/common/metadata/parser.ypp
@@ -28,6 +28,12 @@
 
 #include "parser-wrap.hpp"
 
+/*
+ * Avoid warning about "yynerrs" being unused, seen with bison 3.5.1 + clang 15
+ * on Ubuntu 20.04.
+ */
+BT_DIAG_IGNORE_UNUSED_BUT_SET_VARIABLE
+
 /* Join two lists, put "add" at the end of "head".  */
 static inline void
 _bt_list_splice_tail (struct bt_list_head *add, struct bt_list_head *head)