Cargoify servo

etc/servo_gdb.py

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+# Copyright 2013 The Servo Project Developers. See the COPYRIGHT
+# file at the top-level directory of this distribution.
+#
+# Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+# http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+# <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+# option. This file may not be copied, modified, or distributed
+# except according to those terms.
+
+# A set of simple pretty printers for gdb to make debugging Servo a bit easier.
+
+# To load these, you need to add something like the following
+# to your .gdbinit file.
+#python
+#import sys
+#sys.path.insert(0, '/home/<path to git checkout>/servo/src/etc')
+#import servo_gdb
+#servo_gdb.register_printers(None)
+#end
+
+import gdb
+
+# Print Au in both raw value and CSS pixels
+class AuPrinter:
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        i32_type = gdb.lookup_type("i32")
+        au = self.val.cast(i32_type);
+        return "{0}px ({1} au)".format(au / 60.0, au)
+
+# Print a U8 bitfield as binary
+class BitFieldU8Printer:
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        u8_type = gdb.lookup_type("u8")
+        value = self.val.cast(u8_type);
+        return "[{0:#010b}]".format(int(value))
+
+# Print a struct with fields as children
+class ChildPrinter:
+    def __init__(self, val):
+        self.val = val
+
+    def children(self):
+        children = []
+        for f in self.val.type.fields():
+            children.append( (f.name, self.val[f.name]) )
+        return children
+
+    def to_string(self):
+        return None
+
+# Allow a trusted node to be dereferenced in the debugger
+class TrustedNodeAddressPrinter:
+    def __init__(self, val):
+        self.val = val
+
+    def children(self):
+        node_type = gdb.lookup_type("struct script::dom::node::Node").pointer()
+        value = self.val.cast(node_type)
+        return [('Node', value)]
+
+    def to_string(self):
+        return self.val.address
+
+# Extract a node type ID from enum
+class NodeTypeIdPrinter:
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        u8_ptr_type = gdb.lookup_type("u8").pointer()
+        enum_0 = self.val.address.cast(u8_ptr_type).dereference()
+        enum_type = self.val.type.fields()[int(enum_0)].type;
+        return str(enum_type).lstrip('struct ')
+
+# Printer for std::Option<>
+class OptionPrinter:
+    def __init__(self, val):
+        self.val = val
+
+    def is_some(self):
+        # Get size of discriminator
+        d_size = self.val.type.fields()[0].type.sizeof
+
+        if d_size > 0 and d_size <= 8:
+            # Read first byte to check if None or Some
+            ptr = self.val.address.cast(gdb.lookup_type("unsigned char").pointer())
+            discriminator = int(ptr.dereference())
+            return discriminator != 0
+
+        raise "unhandled discriminator size"
+
+    def children(self):
+        if self.is_some():
+            option_type = self.val.type
+
+            # Get total size and size of value
+            ptr = self.val.address.cast(gdb.lookup_type("unsigned char").pointer())
+            t_size = option_type.sizeof
+            value_type = option_type.fields()[1].type.fields()[1].type
+            v_size = value_type.sizeof
+            data_ptr = (ptr + t_size - v_size).cast(value_type.pointer()).dereference()
+            return [('Some', data_ptr)]
+        return [('None', None)]
+
+    def to_string(self):
+        return None
+
+# Useful for debugging when type is unknown
+class TestPrinter:
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        return "[UNKNOWN - type = {0}]".format(str(self.val.type))
+
+type_map = [
+    ('Au', AuPrinter),
+    ('FlowFlags', BitFieldU8Printer),
+    ('IntrinsicWidths', ChildPrinter),
+    ('PlacementInfo', ChildPrinter),
+    ('TrustedNodeAddress', TrustedNodeAddressPrinter),
+    ('NodeTypeId', NodeTypeIdPrinter),
+    ('Option', OptionPrinter),
+]
+
+def lookup_servo_type (val):
+    val_type = str(val.type)
+    for (type_name, printer) in type_map:
+        if val_type == type_name or val_type.endswith("::"+type_name):
+            return printer(val)
+    return None
+    #return TestPrinter(val)
+
+def register_printers(obj):
+    gdb.pretty_printers.append(lookup_servo_type)