Teach GDB that wchar_t is a built-in type in C++ mode

GDB is currently not aware that wchar_t is a built-in type in C++
mode.  This is usually not a problem because the debug info describes
the type, so when you have a program loaded, you don't notice this.
However, if you try expressions involving wchar_t before a program is
loaded, gdb errors out:

 (gdb) p (wchar_t)-1
 No symbol table is loaded.  Use the "file" command.
 (gdb) p L"hello"
 No type named wchar_t.
 (gdb) ptype L"hello"
 No type named wchar_t.

This commit teaches gdb about the type.  After:

 (gdb) p (wchar_t)-1
 $1 = -1 L'\xffffffff'
 (gdb) p L"hello"
 $2 = L"hello"
 (gdb) ptype L"hello"
 type = wchar_t [6]

Unlike char16_t/char32_t, unfortunately, the underlying type of
wchar_t is implementation dependent, both size and signness.  So this
requires adding a couple new gdbarch hooks.

I grepped the GCC code base for WCHAR_TYPE and WCHAR_TYPE_SIZE, and it
seems to me that the majority of the ABIs have a 4-byte signed
wchar_t, so that's what I made the default for GDB too.  And then I
looked for which ports have a 16-bit and/or unsigned wchar_t, and made
GDB follow suit.

gdb/ChangeLog:
2017-04-12  Pedro Alves  <palves@redhat.com>

	PR gdb/21323
	* c-lang.c (cplus_primitive_types) <cplus_primitive_type_wchar_t>:
	New enum value.
	(cplus_language_arch_info): Register cplus_primitive_type_wchar_t.
	* gdbtypes.h (struct builtin_type) <builtin_wchar>: New field.
	* gdbtypes.c (gdbtypes_post_init): Create the "wchar_t" type.
	* gdbarch.sh (wchar_bit, wchar_signed): New per-arch values.
	* gdbarch.h, gdbarch.c: Regenerate.
	* aarch64-tdep.c (aarch64_gdbarch_init): Override
	gdbarch_wchar_bit and gdbarch_wchar_signed.
	* alpha-tdep.c (alpha_gdbarch_init): Likewise.
	* arm-tdep.c (arm_gdbarch_init): Likewise.
	* avr-tdep.c (avr_gdbarch_init): Likewise.
	* h8300-tdep.c (h8300_gdbarch_init): Likewise.
	* i386-nto-tdep.c (i386nto_init_abi): Likewise.
	* i386-tdep.c (i386_go32_init_abi): Likewise.
	* m32r-tdep.c (m32r_gdbarch_init): Likewise.
	* moxie-tdep.c (moxie_gdbarch_init): Likewise.
	* nds32-tdep.c (nds32_gdbarch_init): Likewise.
	* rs6000-aix-tdep.c (rs6000_aix_init_osabi): Likewise.
	* sh-tdep.c (sh_gdbarch_init): Likewise.
	* sparc-tdep.c (sparc32_gdbarch_init): Likewise.
	* sparc64-tdep.c (sparc64_init_abi): Likewise.
	* windows-tdep.c (windows_init_abi): Likewise.
	* xstormy16-tdep.c (xstormy16_gdbarch_init): Likewise.

gdb/testsuite/ChangeLog:
2017-04-12  Pedro Alves  <palves@redhat.com>

	PR gdb/21323
	* gdb.cp/wide_char_types.c: Include <wchar.h>.
	(wchar): New global.
	* gdb.cp/wide_char_types.exp (wide_char_types_program)
	(do_test_wide_char, wide_char_types_no_program, top level): Add
	wchar_t testing.

3 files changed, 63 insertions, 14 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index e2555e0..7f858e6 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,5 +1,14 @@
 2017-04-12  Pedro Alves  <palves@redhat.com>
 
+	PR gdb/21323
+	* gdb.cp/wide_char_types.c: Include <wchar.h>.
+	(wchar): New global.
+	* gdb.cp/wide_char_types.exp (wide_char_types_program)
+	(do_test_wide_char, wide_char_types_no_program, top level): Add
+	wchar_t testing.
+
+2017-04-12  Pedro Alves  <palves@redhat.com>
+
 	PR c++/21323
 	* gdb.cp/wide_char_types.c: New file.
 	* gdb.cp/wide_char_types.exp: New file.
diff --git a/gdb/testsuite/gdb.cp/wide_char_types.c b/gdb/testsuite/gdb.cp/wide_char_types.c
index 8337cd4..c899b71 100644
--- a/gdb/testsuite/gdb.cp/wide_char_types.c
+++ b/gdb/testsuite/gdb.cp/wide_char_types.c
@@ -17,9 +17,11 @@
 */
 
 #include <uchar.h>
+#include <wchar.h>
 
 char16_t u16 = -1;
 char32_t u32 = -1;
+wchar_t wchar = -1;
 
 int
 main ()
diff --git a/gdb/testsuite/gdb.cp/wide_char_types.exp b/gdb/testsuite/gdb.cp/wide_char_types.exp
index df5c8a8f..6a91350 100644
--- a/gdb/testsuite/gdb.cp/wide_char_types.exp
+++ b/gdb/testsuite/gdb.cp/wide_char_types.exp
@@ -15,14 +15,14 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-# Test GDB's awareness of the char16_t, char32_t (C++11+) built-in
-# types.  We also run most tests here in C mode, and check whether the
-# built-ins are disabled (gdb uses the typedefs in the debug info
-# instead.)
+# Test GDB's awareness of the wchar_t (C++98+) and char16_t, char32_t
+# (C++11+) built-in types.  We also run most tests here in C mode, and
+# check whether the built-ins are disabled (gdb uses the typedefs in
+# the debug info instead.)
 
 standard_testfile
 
-# Test char16_t/char32_t in language LANG, against symbols in
+# Test char16_t/char32_t/wchar_t in language LANG, against symbols in
 # a program.  Lang can be "c", "c++03" or "c++11".  In C++11,
 # char16_t/char32_t are built-in types, and the debug information
 # reflects that (see
@@ -51,16 +51,16 @@ proc wide_char_types_program {lang} {
 	fail "can't run to main"
 	return 0
     }
-    do_test_wide_char $lang "u16" "u32"
+    do_test_wide_char $lang "u16" "u32" "wchar"
 }
 
-# Test char16_t/char32_t in language LANG.  Use CHAR16_EXP and
-# CHAR32_EXP as expression for each of the corresponding types.
-# (E.g., CHAR16_EXP will be u16 when testing against the program, and
-# "(char16_t)-1" when testing the built-in types without a program
-# loaded.)
+# Test char16_t/char32_t/wchar_t in language LANG.  Use CHAR16_EXP,
+# CHAR32_EXP, and WCHAR_EXP as expression for each of the
+# corresponding types.  (E.g., CHAR16_EXP will be u16 when testing
+# against the program, and "(char16_t)-1" when testing the built-in
+# types without a program loaded.)
 
-proc do_test_wide_char {lang char16_exp char32_exp} {
+proc do_test_wide_char {lang char16_exp char32_exp wchar_exp} {
     global gdb_prompt
 
     # Check that the fixed-width wide types are distinct built-in
@@ -78,26 +78,60 @@ proc do_test_wide_char {lang char16_exp char32_exp} {
 	    "char32_t is typedef"
     }
 
+    # wchar_t is a disctinct built-in type in C++03+.
+    if {$lang != "c"} {
+	gdb_test "ptype $wchar_exp" "type = wchar_t" \
+	    "wchar_t is distinct"
+    } else {
+	gdb_test "ptype $wchar_exp" "type = (unsigned )?(long|int|short)" \
+	    "wchar_t is typedef"
+    }
+
     # Check that the fixed-width wide char types are unsigned.
     gdb_test "p $char16_exp" " = 65535 u'\\\\xffff'" \
 	"char16_t is unsigned"
     gdb_test "p $char32_exp" " = 4294967295 U'\\\\xffffffff'" \
 	"char32_t is unsigned"
 
+    # Whether wchar_t is signed is implementation-dependent.  While we
+    # ignore whether GDB got the ABI size/sign details right here,
+    # this at least verifies that the value isn't garbage, and that
+    # GDB correctly outputs the character using the "L" prefix.
+    set test "wchar_t sign"
+    gdb_test_multiple "p $wchar_exp" $test {
+	-re " = 4294967295 L'\\\\xffffffff'\r\n$gdb_prompt $" {
+	    pass "$test (unsigned)"
+	}
+	-re " = 65535 L'\\\\xffff'\r\n$gdb_prompt $" {
+	    pass "$test (unsigned)"
+	}
+	-re " = -1 L'\\\\xffffffff'\r\n$gdb_prompt $" {
+	    pass "$test (signed)"
+	}
+	-re " = -1 L'\\\\xffff'\r\n$gdb_prompt $" {
+	    pass "$test (signed)"
+	}
+    }
+
     # Check sizeof.  These are fixed-width.
     gdb_test "p sizeof($char16_exp)" "= 2" \
 	"sizeof($char16_exp) == 2"
     gdb_test "p sizeof($char32_exp)" "= 4" \
 	"sizeof(char16_t) == 4"
 
+    # Size of wchar_t depends on ABI.
+    gdb_test "p sizeof($wchar_exp)" "= (2|4)" \
+	"sizeof(wchar_t)"
+
     # Test printing wide literal strings.  Note that when testing with
     # no program started, this relies on GDB's awareness of the
     # built-in wide char types.
     gdb_test {p U"hello"} {= U"hello"}
     gdb_test {p u"hello"} {= u"hello"}
+    gdb_test {p L"hello"} {= L"hello"}
 }
 
-# Make sure that the char16_t/char32_t types are recognized as
+# Make sure that the char16_t/char32_t/wchar_t types are recognized as
 # distinct built-in types in C++ mode, even with no program loaded.
 # Check that in C mode, the types are not recognized.
 
@@ -116,8 +150,12 @@ proc wide_char_types_no_program {} {
 	gdb_test "p (char32_t) -1" "No symbol table is loaded.*" \
 	    "char32_t is not built-in"
 
+	gdb_test "p (wchar_t) -1" "No symbol table is loaded.*" \
+	    "wchar_t is not built-in"
+
 	gdb_test {p U"hello"} "No type named char32_t\\\."
 	gdb_test {p u"hello"} "No type named char16_t\\\."
+	gdb_test {p L"hello"} "No type named wchar_t\\\."
     }
 
     # Note GDB does not distinguish C++ dialects, so the fixed-width
@@ -126,7 +164,7 @@ proc wide_char_types_no_program {} {
     with_test_prefix "c++" {
 	gdb_test "set language c++"
 
-	do_test_wide_char "c++11" "(char16_t) -1" "(char32_t) -1"
+	do_test_wide_char "c++11" "(char16_t) -1" "(char32_t) -1" "(wchar_t) -1"
     }
 }