[PATCH v2 3/4] gdb/unittests: PR28413, suppress warnings generated by Gnulib

[Tsukasa OI]

Gnulib generates a warning if the system version of certain functions
are used (to redirect the developer to use Gnulib version).  It caused a
compiler error when...

-   Compiled with Clang
-   -Werror is specified (by default)
-   C++ standard used by Clang is before C++17 (by default as of 15.0.0)
    when this unit test is activated.

This issue is raised as PR28413.

However, previous proposal to fix this issue (a "fix" to Gnulib):
<https://lists.gnu.org/archive/html/bug-gnulib/2021-10/msg00003.html>
was rejected because it ruins the intent of Gnulib warnings.

So, we need a Binutils/GDB-side solution.

This commit tries to deal with this issue on the GDB side.  We have
"include/diagnostics.h" to disable certain warnings only when necessary.

This commit suppresses the Gnulib warnings by adding
DIAGNOSTIC_IGNORE_USER_DEFINED_WARNINGS before including "defs.h".

gdb/ChangeLog:

	pr 28413
	* unittests/string_view-selftests.c: Suppress Gnulib-generated
	warnings when "defs.h" is included.
---
 gdb/unittests/string_view-selftests.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/gdb/unittests/string_view-selftests.c b/gdb/unittests/string_view-selftests.c
index 2d7261d18d3..c1f7799d94c 100644
--- a/gdb/unittests/string_view-selftests.c
+++ b/gdb/unittests/string_view-selftests.c
@@ -23,7 +23,12 @@
 
 #define GNULIB_NAMESPACE gnulib
 
+#include "diagnostics.h"
+
+DIAGNOSTIC_PUSH
+DIAGNOSTIC_IGNORE_USER_DEFINED_WARNINGS
 #include "defs.h"
+DIAGNOSTIC_POP
 #include "gdbsupport/selftest.h"
 #include "gdbsupport/gdb_string_view.h"
 
-- 
2.34.1