[gdb/testsuite] Handle gdb.cp/*.exp with older compiler

When running test-cases gdb.cp/*.exp with gcc 4.8.4, I run into compilation
failures due to the test-cases requiring c++11 and the compiler defaulting
to less than that.

Fix this by compiling with -std=c++11.

This exposes two FAILs in gdb/testsuite/gdb.cp/empty-enum.exp due to
gcc PR debug/16063, so xfail those.

Also require have_compile_flag -std=c++17 in gdb.cp/constexpr-field.exp to
prevent compilation failure.

Tested on x86_64-linux.

gdb/testsuite/gdb.cp/casts.exp

@@ -29,7 +29,12 @@ require allow_cplus_tests
 
 standard_testfile .cc casts03.cc
 
-if {[prepare_for_testing "failed to prepare" $testfile $srcfile {debug c++}]} {
+set opts {}
+lappend opts debug
+lappend opts c++
+lappend opts additional_flags=-std=c++11
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile $opts]} {
     return -1
 }
 

gdb/testsuite/gdb.cp/constexpr-field.exp

@@ -16,6 +16,7 @@
 # This file is part of the gdb testsuite.
 
 require allow_cplus_tests
+require {have_compile_flag -std=c++17}
 
 standard_testfile .cc
 

gdb/testsuite/gdb.cp/empty-enum.exp

@@ -29,7 +29,11 @@
 
 standard_testfile .cc
 
-if {[prepare_for_testing "failed to prepare" $testfile $srcfile]} {
+set opts {}
+lappend opts debug
+lappend opts additional_flags=-std=c++11
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile $opts]} {
     return -1
 }
 
@@ -44,5 +48,30 @@ gdb_continue_to_breakpoint "stop in breakpt"
 gdb_test "print arg1" " = 8"
 gdb_test "print arg2" " = 4"
 
-gdb_test "ptype arg1" "type = enum enum1 : unsigned int \\{\\}"
+
-gdb_test "ptype arg2" "type = enum class enum2 : unsigned char \\{\\}"
+# Xfail for missing DW_AT_type in DW_TAG_enumeration_type, gcc PR debug/16063.
+set have_xfail [expr [test_compiler_info gcc-*] && [gcc_major_version] < 5]
+
+gdb_test_multiple "ptype arg1" "" {
+    -re -wrap "type = enum enum1 : unsigned int \\{\\}" {
+	pass $gdb_test_name
+    }
+    -re -wrap "type = enum enum1 \\{\\}" {
+	if { $have_xfail } {
+	    setup_xfail *-*-* gcc/16063
+	}
+	fail $gdb_test_name
+    }
+}
+
+gdb_test_multiple "ptype arg2" "" {
+    -re -wrap "type = enum class enum2 : unsigned char \\{\\}" {
+	pass $gdb_test_name
+    }
+    -re -wrap "type = enum class enum2 \\{\\}" {
+	if { $have_xfail } {
+	    setup_xfail *-*-* gcc/16063
+	}
+	fail $gdb_test_name
+    }
+}

gdb/testsuite/gdb.cp/koenig.exp

@@ -15,8 +15,13 @@
 
 standard_testfile .cc
 
-if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile} \
+set opts {}
-      {debug c++ additional_flags=-Wno-unused-comparison}] } {
+lappend opts debug
+lappend opts c++
+lappend opts additional_flags=-Wno-unused-comparison
+lappend opts additional_flags=-std=c++11
+
+if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile} $opts] } {
      return -1
 }
 

gdb/testsuite/gdb.cp/method-call-in-c.exp

@@ -20,7 +20,11 @@
 
 standard_testfile .cc
 
-if { [prepare_for_testing "failed to prepare" $testfile $srcfile] } {
+set opts {}
+lappend opts debug
+lappend opts additional_flags=-std=c++11
+
+if { [prepare_for_testing "failed to prepare" $testfile $srcfile $opts] } {
     return -1
 }
 

gdb/testsuite/gdb.cp/paramless.exp

@@ -21,7 +21,12 @@ require allow_cplus_tests
 
 standard_testfile .cc
 
-if {[prepare_for_testing "failed to prepare" $testfile $srcfile {debug c++}]} {
+set opts {}
+lappend opts debug
+lappend opts c++
+lappend opts additional_flags=-std=c++11
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile $opts]} {
     return -1
 }
 

gdb/testsuite/gdb.cp/templates.exp

@@ -22,6 +22,8 @@ require allow_cplus_tests
 standard_testfile .cc
 
 set flags [list debug c++]
+lappend flags additional_flags=-std=c++11
+
 if { [test_compiler_info gcc-*] && [gcc_major_version] >= 10 } {
     # Work around PR gcc/101452.
     lappend flags additional_flags=-DGCC_BUG

gdb/testsuite/gdb.cp/typed-enum.exp

@@ -19,7 +19,12 @@ require allow_cplus_tests
 
 standard_testfile .cc
 
-if {[prepare_for_testing "failed to prepare" $testfile $srcfile {debug c++}]} {
+set opts {}
+lappend opts debug
+lappend opts c++
+lappend opts additional_flags=-std=c++11
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile $opts]} {
     return -1
 }