Fix build errors in with clang in gdb.compile/compile-cplus.c

Clang fails to compile the file, with the following error:
  fatal error: 'iostream' file not found

This prevents the following testcase from executing:
  gdb.compile/compile-cplus.exp

The testcase sets additional_flags when building with GCC, which
this commit causes to also be set when building with clang.  This
makes the testcase fail to build with a different error:
  warning: treating 'c' input as 'c++' when in C++ mode, this behavior
  is deprecated [-Wdeprecated]
so this commit adds -Wno-deprecated in two places to sidestep this.
Note that, while allowing the testcase to build, this commit reveals
failures when the testsuite is built using clang.

gdb/testsuite/ChangeLog:

	* gdb.compile/compile-cplus.exp (additional_flags): Also
	set when building with clang.
	(additional_flags, srcfilesoptions): Pass -Wno-deprecated
	when building with clang.

2 files changed, 20 insertions, 2 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 667dbfd..d4e7220 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,5 +1,12 @@
 2020-05-29  Gary Benson <gbenson@redhat.com>
 
+	* gdb.compile/compile-cplus.exp (additional_flags): Also
+	set when building with clang.
+	(additional_flags, srcfilesoptions): Pass -Wno-deprecated
+	when building with clang.
+
+2020-05-29  Gary Benson <gbenson@redhat.com>
+
 	* gdb.arch/i386-avx.exp (additional_flags): Also set when
 	building with clang.
 	* gdb.arch/i386-sse.exp (additional_flags): Likewise.
diff --git a/gdb/testsuite/gdb.compile/compile-cplus.exp b/gdb/testsuite/gdb.compile/compile-cplus.exp
index cca5b20..85b2f20 100644
--- a/gdb/testsuite/gdb.compile/compile-cplus.exp
+++ b/gdb/testsuite/gdb.compile/compile-cplus.exp
@@ -19,11 +19,16 @@ standard_testfile .c compile-shlib.c compile-constvar.S compile-nodebug.c
 
 get_compiler_info
 set options {}
-if [test_compiler_info gcc*] {
+if { [test_compiler_info gcc*] || [test_compiler_info clang*] } {
     lappend options additional_flags=-g3
     lappend options additional_flags=-std=gnu++11
     lappend options c++
 }
+if [test_compiler_info clang*] {
+    # Treating C input as C++ is deprecated in Clang, so
+    # the build will fail without disabling -Wdeprecated.
+    lappend options additional_flags=-Wno-deprecated
+}
 
 if { ![istarget x86_64-*-* ] || ![is_lp64_target] } {
     verbose "Skipping x86_64 LOC_CONST test."
@@ -34,7 +39,13 @@ set srcfilesoptions [list ${srcfile} ${options}]
 if { $srcfile3 != "" } {
     lappend srcfilesoptions $srcfile3 ${options}
 }
-lappend srcfilesoptions $srcfile4 "nodebug c++"
+set srcfile4options "nodebug c++"
+if [test_compiler_info clang*] {
+    # Treating C input as C++ is deprecated in Clang, so
+    # the build will fail without disabling -Wdeprecated.
+    set srcfile4options "$srcfile4options additional_flags=-Wno-deprecated"
+}
+lappend srcfilesoptions $srcfile4 $srcfile4options
 if { [eval build_executable_from_specs ${testfile}.exp $testfile {$options} ${srcfilesoptions}] } {
     return -1
 }