[1/8] gdb: Add $_cimag and $_creal internal functions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 0c39c190475..705bcaff49f 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,12 @@ 
+2019-03-18  Andrew Burgess  <andrew.burgess@embecosm.com>
+
+	* NEWS: Mention new internal functions.
+	* dwarf2read.c (dwarf2_init_complex_target_type): New function.
+	(read_base_type): Use dwarf2_init_complex_target_type.
+	* value.c (creal_internal_fn): New function.
+	(cimag_internal_fn): New function.
+	(_initialize_values): Register new internal functions.
+
 2019-03-17  Sergei Trofimovich <siarheit@google.com>
 
 	* unittests/string_view-selftests.c: Define
diff --git a/gdb/NEWS b/gdb/NEWS
index c45b3134064..98ab9fe8f99 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -3,6 +3,9 @@ 
 
 *** Changes since GDB 8.3
 
+* Two new convernience functions $_cimag and $_creal that extract the
+  imaginary and real parts respectively from complex numbers.
+
 *** Changes in GDB 8.3
 
 * GDB and GDBserver now support access to additional registers on
diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index 6b9911c5436..00e2a2e0ed6 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,8 @@ 
+2019-03-18  Andrew Burgess  <andrew.burgess@embecosm.com>
+
+	* gdb.texinfo (Convenience Funs): Document '$_creal' and
+	'$_cimag'.
+
 2019-03-14  Simon Marchi  <simon.marchi@efficios.com>
 
 	* gdb.texinfo (GDB/MI Development and Front Ends): Fix closing
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 271739b6cdc..8e7e622e1c5 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -11390,6 +11390,21 @@ 
 Visiting node of type NODE_INTEGER
 @end smallexample
 
+@item $_cimag(@var{value})
+@findex $_cimag@r{, convenience function}
+Return the imaginary part of a complex number @var{value}.
+
+The type of the imaginary part depends on the type of the complex
+number, a @code{float complex} will return an imaginary part of type
+@code{float}.
+
+@item $_creal(@var{value})
+@findex $_creal@r{, convenience function}
+Return the real part of a complex number @var{value}.
+
+The type of the real part depends on the type of the complex number, a
+@code{float complex} will return an real part of type @code{float}.
+
 @end table
 
 @value{GDBN} provides the ability to list and get help on
diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 7c07a10e8c0..d865ff1a2b2 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -17530,6 +17530,40 @@  dwarf2_init_integer_type (struct dwarf2_cu *cu, struct objfile *objfile,
   return type;
 }
 
+/* Initialise and return a floating point type of size BITS suitable for
+   use as a component of a complex number.  The NAME_HINT is passed through
+   when initialising the floating point type and is the name of the complex
+   type.
+
+   As DWARF doesn't currently provide an explicit name for the components
+   of a complex number, but it can be helpful to have these components
+   named, we try to select a suitable name based on the size of the
+   component.  */
+static struct type *
+dwarf2_init_complex_target_type (struct dwarf2_cu *cu,
+				 struct objfile *objfile,
+				 int bits, const char *name_hint)
+{
+  gdbarch *gdbarch = get_objfile_arch (objfile);
+  struct type *tt = nullptr;
+
+  switch (bits)
+    {
+    case 32:
+      tt = builtin_type (gdbarch)->builtin_float;
+      break;
+    case 64:
+      tt = builtin_type (gdbarch)->builtin_double;
+      break;
+    case 128:
+      tt = builtin_type (gdbarch)->builtin_long_double;
+      break;
+    }
+
+  const char *name = (tt == nullptr) ? nullptr : TYPE_NAME (tt);
+  return dwarf2_init_float_type (objfile, bits, name, name_hint);
+}
+
 /* Find a representation of a given base type and install
    it in the TYPE field of the die.  */
 
@@ -17569,7 +17603,7 @@  read_base_type (struct die_info *die, struct dwarf2_cu *cu)
 	type = init_boolean_type (objfile, bits, 1, name);
 	break;
       case DW_ATE_complex_float:
-	type = dwarf2_init_float_type (objfile, bits / 2, NULL, name);
+	type = dwarf2_init_complex_target_type (cu, objfile, bits / 2, name);
 	type = init_complex_type (objfile, name, type);
 	break;
       case DW_ATE_decimal_float:
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 523013bf9b2..b471f374271 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,8 @@ 
+2019-03-18  Andrew Burgess  <andrew.burgess@embecosm.com>
+
+	* gdb.base/complex-parts.c: New file.
+	* gdb.base/complex-parts.exp: New file.
+
 2019-03-14  Tom Tromey  <tromey@adacore.com>
 
 	* gdb.base/style.exp: Add "set style sources" test.
diff --git a/gdb/testsuite/gdb.base/complex-parts.c b/gdb/testsuite/gdb.base/complex-parts.c
new file mode 100644
index 00000000000..243caee0695
--- /dev/null
+++ b/gdb/testsuite/gdb.base/complex-parts.c
@@ -0,0 +1,50 @@ 
+/* Copyright 2019 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* Unlike the other 'complex.c' test, this one uses the "standard" header
+   file to pull in the complex types.  The testing is around printing the
+   complex numbers, and using the convenience function $_cimag and $_creal
+   to extract the parts of the complex numbers.  */
+
+#include <complex.h>
+
+void
+keep_around (volatile void *ptr)
+{
+  asm ("" ::: "memory");
+}
+
+int
+main (void)
+{
+  double complex z1 = 1.5 + 4.5 * I;
+  float complex z2 = 2.5 - 5.5 * I;
+  long double complex z3 = 3.5 + 6.5 * I;
+
+  double d1 = 1.5;
+  float f1 = 2.5;
+  int i1 = 3;
+
+  keep_around (&z1);
+  keep_around (&z2);
+  keep_around (&z3);
+  keep_around (&d1);
+  keep_around (&f1);
+  keep_around (&i1);
+
+  return 0;	/* Break Here.  */
+}
diff --git a/gdb/testsuite/gdb.base/complex-parts.exp b/gdb/testsuite/gdb.base/complex-parts.exp
new file mode 100644
index 00000000000..ce8f4277a8b
--- /dev/null
+++ b/gdb/testsuite/gdb.base/complex-parts.exp
@@ -0,0 +1,62 @@ 
+# Copyright 2019 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+standard_testfile
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile debug]} {
+    return -1
+}
+
+if { ![runto_main] } then {
+    fail "can't run to main"
+    return 0
+}
+
+gdb_breakpoint [gdb_get_line_number "Break Here"]
+gdb_continue_to_breakpoint "breakpt" ".* Break Here\\. .*"
+
+gdb_test "p z1" " = 1.5 \\+ 4.5 \\* I"
+gdb_test "p z2" " = 2.5 \\+ -5.5 \\* I"
+gdb_test "p z3" " = 3.5 \\+ 6.5 \\* I"
+
+gdb_test "ptype z1" " = complex double"
+gdb_test "ptype z2" " = complex float"
+gdb_test "ptype z3" " = complex long double"
+
+gdb_test "p \$_cimag (z1)" " = 4.5"
+gdb_test "ptype \$" " = double"
+
+gdb_test "p \$_cimag (z2)" " = -5.5"
+gdb_test "ptype \$" " = float"
+
+gdb_test "p \$_cimag (z3)" " = 6.5"
+gdb_test "ptype \$" " = long double"
+
+gdb_test "p \$_creal (z1)" " = 1.5"
+gdb_test "ptype \$" " = double"
+
+gdb_test "p \$_creal (z2)" " = 2.5"
+gdb_test "ptype \$" " = float"
+
+gdb_test "p \$_creal (z3)" " = 3.5"
+gdb_test "ptype \$" " = long double"
+
+gdb_test "p \$_cimag (d1)" "expected a complex number"
+gdb_test "p \$_cimag (f1)" "expected a complex number"
+gdb_test "p \$_cimag (i1)" "expected a complex number"
+
+gdb_test "p \$_creal (d1)" "expected a complex number"
+gdb_test "p \$_creal (f1)" "expected a complex number"
+gdb_test "p \$_creal (i1)" "expected a complex number"
diff --git a/gdb/testsuite/gdb.base/default.exp b/gdb/testsuite/gdb.base/default.exp
index ece1428e617..bdae0d471e7 100644
--- a/gdb/testsuite/gdb.base/default.exp
+++ b/gdb/testsuite/gdb.base/default.exp
@@ -601,6 +601,8 @@  set show_conv_list \
 	{$_probe_arg9 = <error: No frame selected>} \
 	{$_probe_arg10 = <error: No frame selected>} \
 	{$_probe_arg11 = <error: No frame selected>} \
+	{$_cimag = <internal function _cimag>} \
+	{$_creal = <internal function _creal>} \
 	{$_isvoid = <internal function _isvoid>} \
     }
 if ![skip_python_tests] {
diff --git a/gdb/value.c b/gdb/value.c
index dc297dfe0f9..eb48094dbe7 100644
--- a/gdb/value.c
+++ b/gdb/value.c
@@ -3933,6 +3933,44 @@  isvoid_internal_fn (struct gdbarch *gdbarch,
   return value_from_longest (builtin_type (gdbarch)->builtin_int, ret);
 }
 
+/* Implementation of the convenience function $_cimag.  Extracts the
+   real part from a complex number.  */
+
+static struct value *
+creal_internal_fn (struct gdbarch *gdbarch,
+		   const struct language_defn *language,
+		   void *cookie, int argc, struct value **argv)
+{
+  if (argc != 1)
+    error (_("You must provide one argument for $_real_from_complex."));
+
+  value *cval = argv[0];
+  type *ctype = check_typedef (value_type (cval));
+  if (TYPE_CODE (ctype) != TYPE_CODE_COMPLEX)
+    error (_("expected a complex number"));
+  return value_from_component (cval, TYPE_TARGET_TYPE (ctype), 0);
+}
+
+/* Implementation of the convenience function $_cimag.  Extracts the
+   imaginary part from a complex number.  */
+
+static struct value *
+cimag_internal_fn (struct gdbarch *gdbarch,
+		   const struct language_defn *language,
+		   void *cookie, int argc,
+		   struct value **argv)
+{
+  if (argc != 1)
+    error (_("You must provide one argument for $_real_from_complex."));
+
+  value *cval = argv[0];
+  type *ctype = check_typedef (value_type (cval));
+  if (TYPE_CODE (ctype) != TYPE_CODE_COMPLEX)
+    error (_("expected a complex number"));
+  return value_from_component (cval, TYPE_TARGET_TYPE (ctype),
+			       TYPE_LENGTH (TYPE_TARGET_TYPE (ctype)));
+}
+
 #if GDB_SELF_TEST
 namespace selftests
 {
@@ -4114,6 +4152,20 @@  Usage: $_isvoid (expression)\n\
 Return 1 if the expression is void, zero otherwise."),
 			 isvoid_internal_fn, NULL);
 
+  add_internal_function ("_creal", _("\
+Extract the real part of a complex number.\n\
+Usage: $_real_from_complex (expression)\n\
+Return the real part of a complex number, the type depends on the\n\
+type of a complex number."),
+			 creal_internal_fn, NULL);
+
+  add_internal_function ("_cimag", _("\
+Extract the imaginary part of a complex number.\n\
+Usage: $_imaginary_from_complex (expression)\n\
+Return the imaginary part of a complex number, the type depends on the\n\
+type of a complex number."),
+			 cimag_internal_fn, NULL);
+
   add_setshow_zuinteger_unlimited_cmd ("max-value-size",
 				       class_support, &max_value_size, _("\
 Set maximum sized value gdb will load from the inferior."), _("\