You can currently do this by checking for other variables to see if any names
match.
In python when stopped in the function below you can do use the API:
(lldb) script
Python Interactive Interpreter. To exit, type 'quit()', 'exit()' or Ctrl-D.
>>> frame_vars = lldb.frame.GetVariables(True, True, True, True)
>>> print frame_vars
(int) v = 1
(int) v = 2
frame_vars is a list of all variables in the current stack frame. They are
ordered correctly so you see your first "v" first and the second one next.
Lets grab the exact lexical block from the current frame:
>>> block = lldb.frame.GetBlock()
This is the block from line 4 - 7 in your source code.
>>> print block.GetVariables(lldb.frame, True, True, True, 0)
(int) v = 2
Note that if we ask the block for its variables, it will only have the
variables contained in that block. Now you can ask "block" for its parent block:
>>> print block.GetParent().GetVariables(lldb.frame, True, True, True, 0)
(int) v = 1
So with all of this you could create a new python command:
#!/usr/bin/python
import lldb
import shlex
@lldb.command("check-shadow")
def check_shadow_command(debugger, command, result, dict):
target = debugger.GetSelectedTarget()
if not target:
print >>result, "invalid target"
return
process = target.GetProcess()
if not process:
print >>result, "invalid process"
return
thread = process.GetSelectedThread()
if not thread:
print >>result, "invalid thread"
return
frame = thread.GetSelectedFrame()
if not frame:
print >>result, "invalid frame"
return
# Parse command line args
command_args = shlex.split(command)
# TODO: add support for using arguments that are passed to this command...
# Make a dictionary of variable name to "SBBlock and SBValue"
var_dict = {}
# Get the deepest most block from the current frame
block = frame.GetBlock()
# Iterate through the block and all of its parents
while block.IsValid():
# Get block variables from the current block only
block_vars = block.GetVariables(frame, True, True, True, 0)
# Iterate through all variables in the current block
for block_var in block_vars:
# Get the variable name and see if we already have a variable by
this name?
block_var_name = block_var.GetName()
if block_var_name in var_dict:
# We already have seen a variable with this name, so it is
shadowed
print block, block_var
print 'is shadowed by:'
shadow_block_and_vars = var_dict[block_var_name]
for shadow_block_and_var in shadow_block_and_vars:
print shadow_block_and_var[0], shadow_block_and_var[1]
# Since we can have multiple shadowed variables, we our variable
# name dictionary to have an array or "block + variable" pairs so
# We can correctly print out all shadowed variables and whow which
# blocks they come from
if block_var_name in var_dict:
var_dict[block_var_name].append([block, block_var])
else:
var_dict[block_var_name] = [[block, block_var]]
# Get the parent block and continue
block = block.GetParent()
I have attached this as a script that you can import:
#!/usr/bin/python
import lldb
import shlex
@lldb.command("check-shadow")
def check_shadow_command(debugger, command, result, dict):
target = debugger.GetSelectedTarget()
if not target:
print >>result, "invalid target"
return
process = target.GetProcess()
if not process:
print >>result, "invalid process"
return
thread = process.GetSelectedThread()
if not thread:
print >>result, "invalid thread"
return
frame = thread.GetSelectedFrame()
if not frame:
print >>result, "invalid frame"
return
# Parse command line args
command_args = shlex.split(command)
# TODO: add support for using arguments that are passed to this command...
# Make a dictionary of variable name to "SBBlock and SBValue"
var_dict = {}
# Get the deepest most block from the current frame
block = frame.GetBlock()
# Iterate through the block and all of its parents
while block.IsValid():
# Get block variables from the current block only
block_vars = block.GetVariables(frame, True, True, True, 0)
# Iterate through all variables in the current block
for block_var in block_vars:
# Get the variable name and see if we already have a variable by this name?
block_var_name = block_var.GetName()
if block_var_name in var_dict:
# We already have seen a variable with this name, so it is shadowed
print block, block_var
print 'is shadowed by:'
shadow_block_and_vars = var_dict[block_var_name]
for shadow_block_and_var in shadow_block_and_vars:
print shadow_block_and_var[0], shadow_block_and_var[1]
# Since we can have multiple shadowed variables, we our variable
# name dictionary to have an array or "block + variable" pairs so
# We can correctly print out all shadowed variables and whow which
# blocks they come from
if block_var_name in var_dict:
var_dict[block_var_name].append([block, block_var])
else:
var_dict[block_var_name] = [[block, block_var]]
# Get the parent block and continue
block = block.GetParent()
Then you can run this:
% lldb a.out
(lldb) command script import /tmp/lldbshadow.py
(lldb) target create "a.out"
(lldb) b main.cpp:6
(lldb) run
Process 423 stopped
* thread #1: tid = 0x46a88f, 0x0000000100000f82 a.out foo() + 18, stop reason =
breakpoint 1.1, queue = com.apple.main-thread
frame #0: 0x0000000100000f82 a.out foo() + 18 at main.cpp:6
3 int v = 1;
4 {
5 int v = 2;
-> 6 ++v;
7 }
8 }
9
(lldb) check-shadow
Block: {id: 46} [0x100000f70-0x100000f8d) (int) v = 1
is shadowed by:
Block: {id: 94} [0x100000f7b-0x100000f8b) (int) v = 2
So yes it is possible, and I have attached an example. Adding a function to
SBValue might not make sense because SBValue objects are used to represent
registers and many other things other than local variables, and there is no
language agnostic rule we could use to implement this correctly at the generic
API level.
Greg Clayton
> On Jun 22, 2016, at 9:43 AM, Bogdan Hopulele via lldb-dev
> <lldb-dev@lists.llvm.org> wrote:
>
> Hi all,
>
> I’m using lldb 3.9 through the C++ API and I’m trying to determine if a local
> variable is shadowed or not with no luck.
> For the code below:
>
> 1. Is there an API call, that I somehow missed, that can tell me that
> (v = 2) shadows (v = 1)?
> 2. Can I rely on their order in the SBValueList object?
> 3. Would you guys think it would be worth adding bool
> SBValue::IsShadowed() const ?
>
>
> 1 void foo()
> 2 {
> 3 int v = 1;
> 4 {
> 5 int v = 2;
> --> 6 ++v;
> 7 }
> 8 }
>
> Thank,
> Bogdan
> National Instruments Romania S.R.L.
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