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[RFA, doc RFA] Implement $_memeq, $_streq, $_strlen


Hi.
I've had several requests for these and I'd like to finally get
these implemented.  And I've long wanted them myself.

Ok to check in?

2012-08-07  Doug Evans  <dje@google.com>

	Add $_memeq, $_streq, $_strlen convenience functions.
	* NEWS: Document them.
	* data-directory/Makefile.in (PYTHON_FILES): Add function/__init__.py,
	function/strfns.py.
	* python/py-type.c (typy_array_1): New function.
	(typy_array): Call it.
	(typy_vector): New function.
	(type_object_methods): Add "vector".
	* python/lib/gdb/function/__init__.py: New file.
	* python/lib/gdb/function/strfns.py: New file.

	doc/
	* gdb.texinfo (Convenience Funs): New node.
	(Types In Python): Document Type.vector.

	testsuite/
	* gdb.python/py-strfns.c: New file.
	* gdb.python/py-strfns.exp: New file.
	* gdb.python/py-type.exp (test_fields): Add vector tests.

Index: NEWS
===================================================================
RCS file: /cvs/src/src/gdb/NEWS,v
retrieving revision 1.538
diff -u -p -r1.538 NEWS
--- NEWS	6 Aug 2012 17:13:26 -0000	1.538
+++ NEWS	7 Aug 2012 21:32:53 -0000
@@ -3,6 +3,16 @@
 
 *** Changes since GDB 7.5
 
+* Python scripting
+
+  ** Vectors can be created with gdb.Type.vector.
+
+* New convenience functions:
+
+  ** $_memeq(buf1, buf2, length)
+  ** $_streq(str1, str2, length)
+  ** $_strlen(str)
+
 * The 'cd' command now defaults to using '~' (the home directory) if not
   given an argument.
 
Index: data-directory/Makefile.in
===================================================================
RCS file: /cvs/src/src/gdb/data-directory/Makefile.in,v
retrieving revision 1.11
diff -u -p -r1.11 Makefile.in
--- data-directory/Makefile.in	11 Apr 2012 05:50:44 -0000	1.11
+++ data-directory/Makefile.in	7 Aug 2012 21:20:29 -0000
@@ -59,7 +59,9 @@ PYTHON_FILES = \
 	gdb/command/__init__.py \
 	gdb/command/pretty_printers.py \
 	gdb/command/prompt.py \
-	gdb/command/explore.py
+	gdb/command/explore.py \
+	gdb/function/__init__.py \
+	gdb/function/strfns.py
 
 FLAGS_TO_PASS = \
 	"prefix=$(prefix)" \
Index: doc/gdb.texinfo
===================================================================
RCS file: /cvs/src/src/gdb/doc/gdb.texinfo,v
retrieving revision 1.998
diff -u -p -r1.998 gdb.texinfo
--- doc/gdb.texinfo	7 Aug 2012 01:11:02 -0000	1.998
+++ doc/gdb.texinfo	7 Aug 2012 21:20:30 -0000
@@ -7558,6 +7558,7 @@ being passed the type of @var{arg} as th
 * Pretty Printing::             Python pretty printing
 * Value History::               Value history
 * Convenience Vars::            Convenience variables
+* Convenience Funs::            Convenience functions
 * Registers::                   Registers
 * Floating Point Hardware::     Floating point hardware
 * Vector Unit::                 Vector Unit
@@ -9311,6 +9312,9 @@ On HP-UX systems, if you refer to a func
 begins with a dollar sign, @value{GDBN} searches for a user or system
 name first, before it searches for a convenience variable.
 
+@node Convenience Funs
+@section Convenience Functions
+
 @cindex convenience functions
 @value{GDBN} also supplies some @dfn{convenience functions}.  These
 have a syntax similar to convenience variables.  A convenience
@@ -9319,6 +9323,28 @@ however, a convenience function is imple
 @value{GDBN}.
 
 @table @code
+
+@item $_memeq(@var{buf1}, @var{buf2}, @var{length})
+@vindex $_memeq@r{, convenience function}
+Returns one if the @var{length} bytes at the addresses given by
+@var{buf1} and @var{buf2} are equal.
+Otherwise it returns zero.
+
+@item $_streq(@var{str1}, @var{str2})
+@vindex $_streq@r{, convenience function}
+Returns one if the @code{C} strings @var{str1} and @var{str2} are equal.
+Otherwise it returns zero.
+
+@item $_strlen(@var{str})
+@vindex $_strlen@r{, convenience function}
+Returns the length of @code{C} string @var{str}.
+
+@end table
+
+@value{GDBN} provides the ability to list and get help on
+convenience functions.
+
+@table @code
 @item help function
 @kindex help function
 @cindex show all convenience functions
@@ -23361,6 +23387,19 @@ second argument is the upper bound of th
 must not be negative, but the bounds can be.
 @end defun
 
+@defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
+Return a new @code{gdb.Type} object which represents a vector of this
+type.  If one argument is given, it is the inclusive upper bound of
+the vector; in this case the lower bound is zero.  If two arguments are
+given, the first argument is the lower bound of the vector, and the
+second argument is the upper bound of the vector.  A vector's length
+must not be negative, but the bounds can be.
+
+The difference between an @code{array} and a @code{vector} is that
+arrays behave like in C: when used in expressions they decay to a pointer
+to the first element whereas vectors are treated as first class values.
+@end defun
+
 @defun Type.const ()
 Return a new @code{gdb.Type} object which represents a
 @code{const}-qualified variant of this type.
Index: python/py-type.c
===================================================================
RCS file: /cvs/src/src/gdb/python/py-type.c,v
retrieving revision 1.39
diff -u -p -r1.39 py-type.c
--- python/py-type.c	18 May 2012 21:02:52 -0000	1.39
+++ python/py-type.c	7 Aug 2012 21:20:31 -0000
@@ -461,10 +461,10 @@ typy_get_composite (struct type *type)
   return type;
 }
 
-/* Return an array type.  */
+/* Helper for typy_array and typy_vector.  */
 
 static PyObject *
-typy_array (PyObject *self, PyObject *args)
+typy_array_1 (PyObject *self, PyObject *args, int is_vector)
 {
   long n1, n2;
   PyObject *n2_obj = NULL;
@@ -503,12 +503,30 @@ typy_array (PyObject *self, PyObject *ar
   TRY_CATCH (except, RETURN_MASK_ALL)
     {
       array = lookup_array_range_type (type, n1, n2);
+      if (is_vector)
+	make_vector_type (array);
     }
   GDB_PY_HANDLE_EXCEPTION (except);
 
   return type_to_type_object (array);
 }
 
+/* Return an array type.  */
+
+static PyObject *
+typy_array (PyObject *self, PyObject *args)
+{
+  return typy_array_1 (self, args, 0);
+}
+
+/* Return a vector type.  */
+
+static PyObject *
+typy_vector (PyObject *self, PyObject *args)
+{
+  return typy_array_1 (self, args, 1);
+}
+
 /* Return a Type object which represents a pointer to SELF.  */
 static PyObject *
 typy_pointer (PyObject *self, PyObject *args)
@@ -1559,6 +1577,14 @@ static PyMethodDef type_object_methods[]
 Return a type which represents an array of objects of this type.\n\
 The bounds of the array are [LOW_BOUND, HIGH_BOUND] inclusive.\n\
 If LOW_BOUND is omitted, a value of zero is used." },
+  { "vector", typy_vector, METH_VARARGS,
+    "vector ([LOW_BOUND,] HIGH_BOUND) -> Type\n\
+Return a type which represents a vector of objects of this type.\n\
+The bounds of the array are [LOW_BOUND, HIGH_BOUND] inclusive.\n\
+If LOW_BOUND is omitted, a value of zero is used.\n\
+Vectors differ from arrays in that if the current language has C-style\n\
+arrays, vectors don't decay to a pointer to the first element.\n\
+They are first class values." },
    { "__contains__", typy_has_key, METH_VARARGS,
      "T.__contains__(k) -> True if T has a field named k, else False" },
   { "const", typy_const, METH_NOARGS,
Index: python/lib/gdb/function/__init__.py
===================================================================
RCS file: python/lib/gdb/function/__init__.py
diff -N python/lib/gdb/function/__init__.py
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ python/lib/gdb/function/__init__.py	7 Aug 2012 21:20:31 -0000
@@ -0,0 +1,14 @@
+# Copyright (C) 2012 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/>.
Index: python/lib/gdb/function/strfns.py
===================================================================
RCS file: python/lib/gdb/function/strfns.py
diff -N python/lib/gdb/function/strfns.py
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ python/lib/gdb/function/strfns.py	7 Aug 2012 21:20:31 -0000
@@ -0,0 +1,91 @@
+# Useful gdb string convenience functions.
+# Copyright (C) 2012 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/>.
+
+"""$_memeq, $_strlen, $_streq"""
+
+import gdb
+
+
+class _MemEq(gdb.Function):
+  """$_memeq - compare bytes of memory
+
+Usage:
+  $_memeq(a, b, len)
+
+Returns:
+  True if len bytes at a and b compare equally.
+"""
+  def __init__(self):
+    super(_MemEq, self).__init__("_memeq")
+
+  def invoke(self, a, b, length):
+    if length < 0:
+      raise ValueError("length must be non-negative")
+    if length == 0:
+      return True
+    # The argument(s) to vector are [low_bound,]high_bound.
+    byte_vector = gdb.lookup_type("char").vector(length - 1)
+    ptr_byte_vector = byte_vector.pointer()
+    a_ptr = a.reinterpret_cast(ptr_byte_vector)
+    b_ptr = b.reinterpret_cast(ptr_byte_vector)
+    return a_ptr.dereference() == b_ptr.dereference()
+
+
+class _StrLen(gdb.Function):
+  """$_strlen - compute string length
+
+Usage:
+  $_strlen(a)
+
+Returns:
+  Length of string a, assumed to be a Nul-terminated C string.
+"""
+  def __init__(self):
+    super(_StrLen, self).__init__("_strlen")
+
+  def invoke(self, a):
+    # We don't care about the encoding here, per se.
+    # We just want a nul-terminated string where each byte is a character.
+    s = a.string("iso-8859-1")
+    return len(s)
+
+
+class _StrEq(gdb.Function):
+  """$_streq - check string equality
+
+Usage:
+  $_streq(a, b)
+
+Returns:
+  True if a and b are strings with the same length and the same characters.
+
+Example (amd64-linux):
+  catch syscall open
+  cond 1 $_streq((char*) $rdi, "foo")
+"""
+  def __init__(self):
+    super(_StrEq, self).__init__("_streq")
+
+  def invoke(self, a, b):
+    # We don't care about the encoding here, per se.
+    # We just want a nul-terminated string where each byte is a character.
+    return a.string("iso-8859-1") == b.string("iso-8859-1")
+
+
+# GDB will import us automagically via gdb/__init__.py.
+_MemEq()
+_StrLen()
+_StrEq()
Index: testsuite/gdb.python/py-strfns.c
===================================================================
RCS file: testsuite/gdb.python/py-strfns.c
diff -N testsuite/gdb.python/py-strfns.c
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.python/py-strfns.c	7 Aug 2012 21:20:31 -0000
@@ -0,0 +1,50 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2012 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/>.  */
+
+const char str1[] = "Hello.";
+const char str2[] = "Hello.";
+const char str3[] = "Goodbye.";
+
+const char buf1[] = { 0, 1, 2, 3 };
+const char buf2[] = { 0, 1, 2, 3 };
+const char buf3[] = { 0, 1, 2, 4 };
+
+static void
+func (const char *arg)
+{
+  return; /* Break func here.  */
+}
+
+static void
+bfunc (const char *arg)
+{
+  return; /* Break bfunc here.  */
+}
+
+int
+main ()
+{
+  func (str1);
+  func (str2);
+  func (str3);
+
+  bfunc (buf1);
+  bfunc (buf2);
+  bfunc (buf3);
+
+  return 0;
+}
Index: testsuite/gdb.python/py-strfns.exp
===================================================================
RCS file: testsuite/gdb.python/py-strfns.exp
diff -N testsuite/gdb.python/py-strfns.exp
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.python/py-strfns.exp	7 Aug 2012 21:20:31 -0000
@@ -0,0 +1,53 @@
+# Copyright (C) 2012 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/>.
+
+# This file is part of the GDB testsuite.  It tests the convenience
+# functions in strfns.py.
+
+load_lib gdb-python.exp
+
+standard_testfile
+
+if { [prepare_for_testing ${testfile}.exp ${testfile} ${srcfile}] } {
+    return -1
+}
+
+if ![runto_main] {
+    return 0
+}
+
+# Skip all tests if Python scripting is not enabled.
+if { [skip_python_tests] } { continue }
+
+gdb_test "p \$_streq (str1, str2)" " = 1"
+gdb_test "p \$_streq (str1, str3)" " = 0"
+
+gdb_test "p \$_strlen (str1)" " = 6"
+gdb_test "p \$_strlen (buf1)" " = 0"
+
+gdb_test "p \$_memeq (buf1, buf2, 4)" " = 1"
+gdb_test "p \$_memeq (buf1, buf3, 4)" " = 0"
+
+# Verify use in a conditional breakpoint.
+
+gdb_breakpoint [gdb_get_line_number "Break func here."]
+gdb_test_no_output "condition \$bpnum \$_streq (arg, \"Goodbye.\")"
+gdb_continue_to_breakpoint "Break func here."
+gdb_test "p arg" "= $hex <str3> \"Goodbye.\""
+
+gdb_breakpoint [gdb_get_line_number "Break bfunc here."]
+gdb_test_no_output "condition \$bpnum \$_memeq (arg, buf3, 4)"
+gdb_continue_to_breakpoint "Break bfunc here."
+gdb_test "p /d {char\[4\]} arg" "= \\{0, 1, 2, 4\\}"
Index: testsuite/gdb.python/py-type.exp
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.python/py-type.exp,v
retrieving revision 1.24
diff -u -p -r1.24 py-type.exp
--- testsuite/gdb.python/py-type.exp	22 Jun 2012 17:59:33 -0000	1.24
+++ testsuite/gdb.python/py-type.exp	7 Aug 2012 21:20:31 -0000
@@ -114,12 +114,27 @@ proc test_fields {lang} {
   gdb_test "python print len(fields)" "1" "Check the number of fields"
   gdb_test "python print fields\[0\].type" "<range type>" "Check array field type"
 
+  # Test gdb.Type.array.
   gdb_test "python print ar\[0\].cast(ar\[0\].type.array(1))" \
       ".1, 2." "cast to array with one argument"
   gdb_test "python print ar\[0\].cast(ar\[0\].type.array(0, 1))" \
       ".1, 2." "cast to array with two arguments"
 
   gdb_test "python print ar\[0\].type == ar\[0\].type" "True"
+
+  # Test gdb.Type.vector.
+  # Note: vectors cast differently than arrays.  Here ar[0] is replicated
+  # for the size of the vector.
+  gdb_py_test_silent_cmd \
+      "python vec1 = ar\[0\].cast(ar\[0\].type.vector(1))" "set vec1" 1
+  gdb_test "python print vec1" ".1, 1." "cast to vector with one argument"
+  gdb_py_test_silent_cmd \
+      "python vec2 = ar\[0\].cast(ar\[0\].type.vector(0, 1))" "set vec2" 1
+  gdb_test "python print vec2" ".1, 1." "cast to vector with two arguments"
+  gdb_test "python print vec1 == vec2" "True"
+  gdb_py_test_silent_cmd \
+      "python vec3 = ar\[1\].cast(ar\[1\].type.vector(1))" "set vec3" 1
+  gdb_test "python print vec1 == vec3" "False"
 }
 
 proc test_enums {} {


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