libstdc++: Add xfail to pretty printer tests that fail in C++20

For some reason the type printer for std::string doesn't work in C++20
mode, so std::basic_string<char, char_traits<char>, allocator<char> is
printed out in full rather than being shown as std::string. It's
probably related to the fact that the extern template declarations are
disabled for C++20, but I don't know why that affects GDB.

For now I'm just marking the relevant tests as XFAIL. That requires
adding support for target selectors to individual GDB directives such as
note-test and whatis-regexp-test.

libstdc++-v3/ChangeLog:

	* testsuite/lib/gdb-test.exp: Add target selector support to the
	dg-final directives.
	* testsuite/libstdc++-prettyprinters/80276.cc: Add xfail for
	C++20.
	* testsuite/libstdc++-prettyprinters/libfundts.cc: Likewise.
	* testsuite/libstdc++-prettyprinters/prettyprinters.exp: Tweak
	comment.

4 files changed, 45 insertions, 26 deletions

diff --git a/libstdc++-v3/testsuite/lib/gdb-test.exp b/libstdc++-v3/testsuite/lib/gdb-test.exp
index f993355..db0fc2f 100644
--- a/libstdc++-v3/testsuite/lib/gdb-test.exp
+++ b/libstdc++-v3/testsuite/lib/gdb-test.exp
@@ -50,40 +50,48 @@ proc get_line_number {filename marker} {
     return $gdb_markers($filename,$marker)
 }
 
-# Make note of a gdb test.  A test consists of a variable name and an
-# expected result.
-proc note-test {var result} {
+proc register_gdb_test {var result kind rexp selector} {
     global gdb_tests
 
-    lappend gdb_tests $var $result print 0
+    set xfail 0
+    if {[string length $selector] > 0} {
+	switch [dg-process-target $selector] {
+	    "N" { return }
+	    "S" { }
+	    "P" { }
+	    "F" { set xfail 1 }
+	}
+    }
+
+    lappend gdb_tests $var $result $kind $rexp $xfail
+}
+
+# Make note of a gdb test.  A test consists of a variable name and an
+# expected result, and an optional target selector.
+proc note-test {var result {selector {}}} {
+    register_gdb_test $var $result print 0 $selector
 }
 
 # A test that uses a regular expression.  This is like note-test, but
 # the result is a regular expression that is matched against the
 # output.
-proc regexp-test {var result} {
-    global gdb_tests
-
-    lappend gdb_tests $var $result print 1
+proc regexp-test {var result {selector {}}} {
+    register_gdb_test $var $result print 1 $selector
 }
 
 # A test of 'whatis'.  This tests a type rather than a variable.
-proc whatis-test {var result} {
-    global gdb_tests
-
-    lappend gdb_tests $var $result whatis 0
+proc whatis-test {var result {selector {}}} {
+    register_gdb_test $var $result whatis 0 $selector
 }
 
 # A test of 'whatis' that uses a regular expression. This tests a type rather
 # than a variable.
-proc whatis-regexp-test {var result} {
-    global gdb_tests
-
-    lappend gdb_tests $var $result whatis 1
+proc whatis-regexp-test {var result {selector {}}} {
+    register_gdb_test $var $result whatis 1 $selector
 }
 
 # Utility for testing variable values using gdb, invoked via dg-final.
-# Tests all tests indicated by note-test and regexp-test.
+# Tests all tests indicated by note-test, whatis-test, and the regexp versions.
 #
 # Argument 0 is the marker on which to put a breakpoint
 # Argument 2 handles expected failures and the like
@@ -144,7 +152,7 @@ proc gdb-test { marker {selector {}} {load_xmethods 0} } {
     puts $fd "info share"
 
     set count 0
-    foreach {var result kind rexp} $gdb_tests {
+    foreach {var result kind rexp xfail} $gdb_tests {
 	incr count
 	set gdb_var($count) $var
 	set gdb_expected($count) $result
@@ -152,6 +160,7 @@ proc gdb-test { marker {selector {}} {load_xmethods 0} } {
 	    if {$do_whatis_tests} {
 		set gdb_is_type($count) 1
 		set gdb_is_regexp($count) $rexp
+		set gdb_is_xfail($count) $xfail
 		set gdb_command($count) "whatis $var"
 	    } else {
 	        unsupported "$testname"
@@ -161,6 +170,7 @@ proc gdb-test { marker {selector {}} {load_xmethods 0} } {
 	} else {
 	    set gdb_is_type($count) 0
 	    set gdb_is_regexp($count) $rexp
+	    set gdb_is_xfail($count) $xfail
 	    set gdb_command($count) "print $var"
 	}
 	puts $fd $gdb_command($count)
@@ -198,11 +208,20 @@ proc gdb-test { marker {selector {}} {load_xmethods 0} } {
 	    }
 
 	    if {$match} {
-		pass "$testname $gdb_command($test_counter)"
+		if {$gdb_is_xfail($test_counter)} {
+		    xpass "$testname $gdb_command($test_counter)"
+		    verbose " matched =>$first<="
+		} else {
+		    pass "$testname $gdb_command($test_counter)"
+		}
 	    } else {
-		fail "$testname $gdb_command($test_counter)"
-		verbose "     got =>$first<="
-		verbose "expected =>$gdb_expected($test_counter)<="
+		if {$gdb_is_xfail($test_counter)} {
+		    xfail "$testname $gdb_command($test_counter)"
+		} else {
+		    fail "$testname $gdb_command($test_counter)"
+		    verbose "     got =>$first<="
+		    verbose "expected =>$gdb_expected($test_counter)<="
+		}
 	    }
 
 	    if {$test_counter == $count} {
diff --git a/libstdc++-v3/testsuite/libstdc++-prettyprinters/80276.cc b/libstdc++-v3/testsuite/libstdc++-prettyprinters/80276.cc
index 1443f2a..00255c9 100644
--- a/libstdc++-v3/testsuite/libstdc++-prettyprinters/80276.cc
+++ b/libstdc++-v3/testsuite/libstdc++-prettyprinters/80276.cc
@@ -46,7 +46,7 @@ main()
   // { dg-final { whatis-regexp-test p1 "std::unique_ptr<std::(__debug::)?vector<std::unique_ptr<std::(__debug::)?vector<int>\\*>>>" } }
   // { dg-final { whatis-regexp-test p2 "std::unique_ptr<std::(__debug::)?vector<std::unique_ptr<std::(__debug::)?set<int>\\*>>\\\[\\\]>" } }
   // { dg-final { whatis-regexp-test p3 "std::unique_ptr<std::(__debug::)?set<std::unique_ptr<std::(__debug::)?vector<int>\\*>>\\\[10\\\]>" } }
-  // { dg-final { whatis-regexp-test p4 "std::unique_ptr<std::(__debug::)?vector<std::unique_ptr<std::(__debug::)?list<std::string>\\\[\\\]>>\\\[99\\\]>" } }
+  // { dg-final { whatis-regexp-test p4 "std::unique_ptr<std::(__debug::)?vector<std::unique_ptr<std::(__debug::)?list<std::string>\\\[\\\]>>\\\[99\\\]>" { xfail c++20 } } }
 
   placeholder(&p1);		// Mark SPOT
   placeholder(&p2);
diff --git a/libstdc++-v3/testsuite/libstdc++-prettyprinters/libfundts.cc b/libstdc++-v3/testsuite/libstdc++-prettyprinters/libfundts.cc
index 67d177b..af948e0 100644
--- a/libstdc++-v3/testsuite/libstdc++-prettyprinters/libfundts.cc
+++ b/libstdc++-v3/testsuite/libstdc++-prettyprinters/libfundts.cc
@@ -50,7 +50,7 @@ main()
   om = std::map<int, double>{ {1, 2.}, {3, 4.}, {5, 6.} };
 // { dg-final { regexp-test om {std::experimental::optional<std::(__debug::)?map<int, double>> containing std::(__debug::)?map with 3 elements = {\[1\] = 2, \[3\] = 4, \[5\] = 6}} } }
   optional<std::string> os{ "stringy" };
-// { dg-final { note-test os {std::experimental::optional<std::string> = {[contained value] = "stringy"}} } }
+// { dg-final { note-test os {std::experimental::optional<std::string> = {[contained value] = "stringy"}} { xfail c++20 } } }
 
   any a;
 // { dg-final { note-test a {std::experimental::any [no contained value]} } }
@@ -61,7 +61,7 @@ main()
   any ap = (void*)nullptr;
 // { dg-final { note-test ap {std::experimental::any containing void * = {[contained value] = 0x0}} } }
   any as = *os;
-// { dg-final { note-test as {std::experimental::any containing std::string = {[contained value] = "stringy"}} } }
+// { dg-final { note-test as {std::experimental::any containing std::string = {[contained value] = "stringy"}} { xfail c++20 } } }
   any as2("stringiest");
 // { dg-final { regexp-test as2 {std::experimental::any containing const char \* = {\[contained value\] = 0x[[:xdigit:]]+ "stringiest"}} } }
   any am = *om;
diff --git a/libstdc++-v3/testsuite/libstdc++-prettyprinters/prettyprinters.exp b/libstdc++-v3/testsuite/libstdc++-prettyprinters/prettyprinters.exp
index 9cd3a26..96686b2 100644
--- a/libstdc++-v3/testsuite/libstdc++-prettyprinters/prettyprinters.exp
+++ b/libstdc++-v3/testsuite/libstdc++-prettyprinters/prettyprinters.exp
@@ -49,7 +49,7 @@ gdb-dg-runtest [lsort [glob $srcdir/$subdir/*.cc]] \
 
 if { [check_effective_target_lto] } {
   append cxxflags " -flto"
-  # work around sourceware.org 20882
+  # Work around linker bug https://sourceware.org/PR20882
   regsub {^(.*)-Wl,--gc-sections(.*)$} $cxxldflags {\1\2} cxxldflags
   gdb-dg-runtest [lsort [glob $srcdir/$subdir/*.cc]] \
     "" "$DEFAULT_CXXFLAGS -flto $PCH_CXXFLAGS"