In theory what you're doing looks like it should be supported. I am not sure
why your example is failing the way it is.
Is your variable a global maybe?
Also, using the variable name is the wrong thing to do. If you have a class
with a std::string member, the name is going to return the wrong thing. You
would want to at least use the expression path - and even then there are some
cases where we can't cons up a proper expression path.
Sent from my iPhone
> On Apr 13, 2016, at 11:02 AM, Jeffrey Tan <jeffrey.fu...@gmail.com> wrote:
>
> I did a quick testing to call SBFrame.EvaluateExpression('string.c_str()')
> for the summary. The result shows valobj.GetFrame() returns None so does this
> mean this is not supported?
>
> def DoTest(valobj,internal_dict):
> print "valobj: %s" % valobj
> print "valobj.GetFrame(): %s" % valobj.GetFrame()
> summaryValue = valobj.GetFrame().EvaluateExpression(valobj.name +
> '.c_str()')
> print "summaryValue: %s" % summaryValue
> return 'Summary from c_str(): %s ' % summaryValue.GetSummary()
>
> type summary add -F DoTest -x "std::fbstring_core<char>"
>
> Output:
> valobj.GetFrame(): No value
> summaryValue: No value
> valobj: (std::string) $6 = {
> store_ = Summary from c_str(): None
> }
>
> Jeffrey
>
>> On Wed, Apr 13, 2016 at 10:11 AM, Jeffrey Tan <jeffrey.fu...@gmail.com>
>> wrote:
>> One quick question: do we support getting type summary string from inferior
>> method call? After reading our own fbstring_core code, I found I need to
>> mirror a lot of what fbstring_core.c_str() method is doing in python. I
>> wonder if we can just call ${var.c_str()} as the type summary? I suspect one
>> of the concern is side-effect(the inferior method may throw exception or
>> cause problems) but I would not see why this can't be done. By allowing this
>> we can keep the data formatter truth one copy(in source code) instead of
>> potential out-of-sync(let say the std::string author decided to change it
>> implementation, the python data formatter associated with it needs to be
>> modified at the same time which is a maintain nightmare).
>>
>> Jeffrey
>>
>>> On Thu, Apr 7, 2016 at 10:33 AM, Enrico Granata <egran...@apple.com> wrote:
>>>
>>>> On Apr 6, 2016, at 7:31 PM, Jeffrey Tan <jeffrey.fu...@gmail.com> wrote:
>>>>
>>>> Thanks Enrico. This is very detailed! I will take a look.
>>>> Btw: originally, I was hoping that data formatter can be added without
>>>> changing the source code. Like giving a xml/json format file telling lldb
>>>> the memory layout/structure of the data structure, lldb can parse the
>>>> xml/json and deduce the formatting. This is approach used by data
>>>> visualizer in VS debugger:
>>>> https://msdn.microsoft.com/en-us/library/jj620914.aspx
>>>> This will make adding data formatter more extensible/flexible. Any reason
>>>> we did not take this approach?
>>>
>>> The way I understand the Natvis system, it allows one to provide a bunch of
>>> expressions that describe how the debugger would go about retrieving the
>>> interesting data bits
>>> This has the bonus of being really easy, since you’re writing code in the
>>> same language/context of the types you’re formatting
>>> On the other hand it has a few drawbacks, in terms of performance as well
>>> as safety (imagine trying to run code on an object when said object is in
>>> an incoherent state)
>>> The LLDB approach, on the other hand, is that you should try to not run
>>> code when providing these data formatters. In order to do that, we vend an
>>> API that can do things such as retrieve child values, read memory, cast
>>> values, …, all without code execution
>>> Once you have this kind of API that is not expressed in your source
>>> language, you might just as well describe it in a scripting language. Hence
>>> were born the Python data formatters.
>>> In order for us to gain even more performance for native system types that
>>> we know we’re gonna run into all the time, we then switched a bunch of the
>>> “mission critical” formatters from Python to C++
>>> The Python extension points are still available, as Jim pointed out, and
>>> you are more than welcome to use those instead of modifying the debugger
>>> core
>>>
>>>> Jeffrey
>>>>
>>>>> On Wed, Apr 6, 2016 at 11:49 AM, Enrico Granata <egran...@apple.com>
>>>>> wrote:
>>>>>
>>>>>> On Apr 5, 2016, at 2:42 PM, Jeffrey Tan <jeffrey.fu...@gmail.com> wrote:
>>>>>>
>>>>>> Hi Enrico,
>>>>>>
>>>>>> Any suggestion/example how to add a data formatter for our own STL
>>>>>> string? From the output below I can see we are using our own
>>>>>> "fbstring_core" which I assume I need to write a type summary for this
>>>>>> type:
>>>>>>
>>>>>> frame variable corpus -T
>>>>>> (const string &const) corpus = error: summary string parsing error: {
>>>>>> (std::fbstring_core<char>) store_ = {
>>>>>> (std::fbstring_core<char>::(anonymous union)) = {
>>>>>> (char [24]) small_ = "www"
>>>>>> (std::fbstring_core<char>::MediumLarge) ml_ = {
>>>>>> (char *) data_ = 0x0000000000777777
>>>>>> "H\x89U\xa8H\x89M\xa0L\x89E\x98H\x8bE\xa8H\x89��_U��D\x88e�H\x8bE\xa0H\x89��]U��H\x89�H\x8dE�H\x89�H\x89���
>>>>>> ��L\x8dm�H\x8bE\x98H\x89��IU��\x88]�L\x8be\xb0L\x89��
>>>>>> (std::size_t) size_ = 0
>>>>>> (std::size_t) capacity_ = 1441151880758558720
>>>>>> }
>>>>>> }
>>>>>> }
>>>>>> }
>>>>>
>>>>> Admittedly, this is going to be a little vague since I haven’t really
>>>>> seen your code and I am only working off of one sample
>>>>>
>>>>> There’s going to be two parts to getting this to work:
>>>>>
>>>>> Part 1 - Formatting fbstring_core
>>>>>
>>>>> At a glance, an fbstring_core<char> can be backed by two representations.
>>>>> A “small” representation (a char array), and a “medium/large"
>>>>> representation (a char* + a size)
>>>>> I assume that the way you tell one from the other is
>>>>>
>>>>> if (size == 0) small
>>>>> else medium-large
>>>>>
>>>>> If my assumption is not correct, you’ll need to discover what the correct
>>>>> discriminator logic is - the class has to know, and so do you :-)
>>>>>
>>>>> Armed with that knowledge, look in lldb
>>>>> source/Plugins/Language/CPlusPlus/Formatters/LibCxx.cpp
>>>>> There’s a bunch of code that deals with formatting llvm’s libc++
>>>>> std::string - which follows a very similar logic to your class
>>>>>
>>>>> ExtractLibcxxStringInfo() is the function that handles discovering which
>>>>> layout the string uses - where the data lives - and how much data there is
>>>>>
>>>>> Once you have told yourself how much data there is (the size) and where
>>>>> it lives (array or pointer), LibcxxStringSummaryProvider() has the easy
>>>>> task - it sets up a StringPrinter, tells it how much data to print, where
>>>>> to get it from, and then delegates the StringPrinter to do the grunt work
>>>>> StringPrinter is a nifty little tool - it can handle generating summaries
>>>>> for different kinds of strings (UTF8? UTF16? we got it - is a \0 a
>>>>> terminator? what quote character would you like? …) - you point it at
>>>>> some data, set up a few options, and it will generate a printable
>>>>> representation for you - if your string type is doing anything out of the
>>>>> ordinary, let’s talk - I am definitely open to extending StringPrinter to
>>>>> handle even more magic
>>>>>
>>>>> Part 2 - Teaching std::string that it can be backed by an fbstring_core
>>>>>
>>>>> At the end of part 1, you’ll probably end up with a
>>>>> FBStringCoreSummaryProvider() - now you need to teach LLDB about it
>>>>> The obvious thing you could do would be to go in
>>>>> CPlusPlusLanguage::GetFormatters() add a
>>>>> LoadFBStringFormatter(g_category) to it - and then imitate - say -
>>>>> LoadLibCxxFormatters()
>>>>>
>>>>> AddCXXSummary(cpp_category_sp,
>>>>> lldb_private::formatters::FBStringCoreSummaryProvider, “fbstringcore
>>>>> summary provider", ConstString(“std::fbstring_core<.+>"),
>>>>> stl_summary_flags, true);
>>>>>
>>>>> That will work - but what you would see is:
>>>>>
>>>>>> (const string &const) corpus = error: summary string parsing error: {
>>>>>> (std::fbstring_core<char>) store_ = “www"
>>>>>
>>>>> You wanna do
>>>>>
>>>>> (lldb) log enable lldb formatters
>>>>> (lldb) frame variable -T corpus
>>>>>
>>>>> It will list one or more typenames - the most specific one is the one you
>>>>> like (e.g. for libc++ we get std::__1::string - this is how we tell
>>>>> ourselves this is the std::string from libc++)
>>>>> Once you find that typename, you’ll make a new formatter -
>>>>> FBStringSummaryProvider() - and register that formatter with that very
>>>>> specific typename
>>>>>
>>>>> All that FBStringSummaryProvider() has to do is get the “store_” member
>>>>> (ValueObject::GetChildMemberWithName() is your friend) - and pass it down
>>>>> to FBStringCoreSummaryProvider()
>>>>>
>>>>>
>>>>> I understand this may seem a little convoluted and arcane at first - but
>>>>> feel free to ask more questions, and I’ll try to help out!
>>>>>
>>>>>> Thanks.
>>>>>> Jeffrey
>>>>>>
>>>>>>> On Mon, Mar 28, 2016 at 11:38 AM, Enrico Granata <egran...@apple.com>
>>>>>>> wrote:
>>>>>>> This is kind of orthogonal to your problem, but the reason why you are
>>>>>>> not seeing the kind of simplified printing Greg is suggesting, is
>>>>>>> because your std::string doesn’t look like any of the kinds we recognize
>>>>>>>
>>>>>>> Specifically, LLDB data formatters work by matching against type names,
>>>>>>> and once they recognize a typename, then they try to inspect the
>>>>>>> variable in order to grab a summary
>>>>>>> In your example, your std::string exposes a layout that we are not
>>>>>>> handling - hence we bail out of the formatter and we fall back to the
>>>>>>> raw view
>>>>>>>
>>>>>>> If you want pretty printing to work, you’ll need to write a data
>>>>>>> formatter
>>>>>>>
>>>>>>> There are a few avenues. The obvious easy one is to extend the existing
>>>>>>> std::string formatter to recognize your type’s internal layout.
>>>>>>> If one were signing up for more infrastructure work, they could decide
>>>>>>> to try and detect shared library loads and load formatters that match
>>>>>>> with whatever libraries are being loaded.
>>>>>>>
>>>>>>>> On Mar 28, 2016, at 9:47 AM, Greg Clayton via lldb-dev
>>>>>>>> <lldb-dev@lists.llvm.org> wrote:
>>>>>>>>
>>>>>>>> So you need to be prepared to escape any text that can have special
>>>>>>>> characters. A "std::string" or any container can contain special
>>>>>>>> characters. If you are encoding stuff into JSON, you will either need
>>>>>>>> to escape any special characters, or hex encode the string into ASCII
>>>>>>>> hex bytes.
>>>>>>>>
>>>>>>>> In debuggers we often get bogus data because variables are not
>>>>>>>> initialized, but the compiler tells us that a variable is valid in
>>>>>>>> address range [0x1000-0x2000), but it actually is [0x1200-0x2000). If
>>>>>>>> we read a variable in this case, a std::string might contain bogus
>>>>>>>> data and the bytes might not make sense. So you always have to be
>>>>>>>> prepared for bad data.
>>>>>>>>
>>>>>>>> If we look at:
>>>>>>>>
>>>>>>>> store_ = {
>>>>>>>> = {
>>>>>>>> small_ = "www"
>>>>>>>> ml_ = (data_ =
>>>>>>>> "��UH\x89�H�}�H\x8bE�]ÐUH\x89�H��H\x89}�H\x8bE�H\x89��~\xb4��\x90��UH\x89�SH\x83�H\x89}�H�u�H�E�H���\x9e���H\x8b\x18H\x8bE�H���O\xb4��H\x89ƿ\b",
>>>>>>>> size_ = 0, capacity_ = 1441151880758558720)
>>>>>>>> }
>>>>>>>> }
>>>>>>>> }
>>>>>>>>
>>>>>>>> We can see the "size_" is zero, and capacity_ is 1441151880758558720
>>>>>>>> (which is 0x1400000000000000). "data_" seems to be some random
>>>>>>>> pointer.
>>>>>>>>
>>>>>>>> On MacOSX, we have a special formatting code that displays std::string
>>>>>>>> in CPlusPlusLanguage.cpp that gets installed in the
>>>>>>>> LoadLibCxxFormatters() or LoadLibStdcppFormatters() functions with
>>>>>>>> code like:
>>>>>>>>
>>>>>>>> lldb::TypeSummaryImplSP std_string_summary_sp(new
>>>>>>>> CXXFunctionSummaryFormat(stl_summary_flags,
>>>>>>>> lldb_private::formatters::LibcxxStringSummaryProvider, "std::string
>>>>>>>> summary provider"));
>>>>>>>>
>>>>>>>> cpp_category_sp->GetTypeSummariesContainer()->Add(ConstString("std::__1::string"),
>>>>>>>> std_string_summary_sp);
>>>>>>>>
>>>>>>>> Special flags are set on std::string to say "don't show children of
>>>>>>>> this and just show a summary" So if a std::string contained "hello".
>>>>>>>> So for the following code:
>>>>>>>>
>>>>>>>> std::string h ("hello");
>>>>>>>>
>>>>>>>> You should just see:
>>>>>>>>
>>>>>>>> (lldb) fr var h
>>>>>>>> (std::__1::string) h = "hello"
>>>>>>>>
>>>>>>>> If you take a look at the normal value in the raw we see:
>>>>>>>>
>>>>>>>> (lldb) fr var --raw h
>>>>>>>> (std::__1::string) h = {
>>>>>>>> __r_ = {
>>>>>>>> std::__1::__libcpp_compressed_pair_imp<std::__1::basic_string<char,
>>>>>>>> std::__1::char_traits<char>, std::__1::allocator<char> >::__rep,
>>>>>>>> std::__1::allocator<char>, 2> = {
>>>>>>>> __first_ = {
>>>>>>>> = {
>>>>>>>> __l = {
>>>>>>>> __cap_ = 122511465736202
>>>>>>>> __size_ = 0
>>>>>>>> __data_ = 0x0000000000000000
>>>>>>>> }
>>>>>>>> __s = {
>>>>>>>> = {
>>>>>>>> __size_ = '\n'
>>>>>>>> __lx = '\n'
>>>>>>>> }
>>>>>>>> __data_ = {
>>>>>>>> [0] = 'h'
>>>>>>>> [1] = 'e'
>>>>>>>> [2] = 'l'
>>>>>>>> [3] = 'l'
>>>>>>>> [4] = 'o'
>>>>>>>> [5] = '\0'
>>>>>>>> [6] = '\0'
>>>>>>>> [7] = '\0'
>>>>>>>> [8] = '\0'
>>>>>>>> [9] = '\0'
>>>>>>>> [10] = '\0'
>>>>>>>> [11] = '\0'
>>>>>>>> [12] = '\0'
>>>>>>>> [13] = '\0'
>>>>>>>> [14] = '\0'
>>>>>>>> [15] = '\0'
>>>>>>>> [16] = '\0'
>>>>>>>> [17] = '\0'
>>>>>>>> [18] = '\0'
>>>>>>>> [19] = '\0'
>>>>>>>> [20] = '\0'
>>>>>>>> [21] = '\0'
>>>>>>>> [22] = '\0'
>>>>>>>> }
>>>>>>>> }
>>>>>>>> __r = {
>>>>>>>> __words = {
>>>>>>>> [0] = 122511465736202
>>>>>>>> [1] = 0
>>>>>>>> [2] = 0
>>>>>>>> }
>>>>>>>> }
>>>>>>>> }
>>>>>>>> }
>>>>>>>> }
>>>>>>>> }
>>>>>>>> }
>>>>>>>>
>>>>>>>> So the main question is why are our "std::string" formatters not
>>>>>>>> kicking in for you. That comes down to a typename match, or the format
>>>>>>>> of the string isn't what the formatter is expecting.
>>>>>>>>
>>>>>>>> But again, since you std::string can contain anything, you will need
>>>>>>>> to escape any and all text that is encoded into JSON to ensure it
>>>>>>>> doesn't contain anything JSON can't deal with.
>>>>>>>>
>>>>>>>>> On Mar 27, 2016, at 9:20 PM, Jeffrey Tan via lldb-dev
>>>>>>>>> <lldb-dev@lists.llvm.org> wrote:
>>>>>>>>>
>>>>>>>>> Thanks Siva. All the DW_TAG_member related errors seems to go away
>>>>>>>>> after patching with your fix. The current problem is handling the
>>>>>>>>> decoding.
>>>>>>>>>
>>>>>>>>> Here is the correct decoding from gdb whic might be useful:
>>>>>>>>> (gdb) p corpus
>>>>>>>>> $3 = (const std::string &) @0x7fd133cfb888: {
>>>>>>>>> static npos = 18446744073709551615, store_ = {
>>>>>>>>> static kIsLittleEndian = <optimized out>,
>>>>>>>>> static kIsBigEndian = <optimized out>, {
>>>>>>>>> small_ = "www", '\000' <repeats 20 times>, "\024", ml_ = {
>>>>>>>>> data_ = 0x777777 <std::_Any_data::_M_access<void
>>>>>>>>> folly::fibers::Baton::waitFiber<folly::fibers::FirstArgOf<facebook::servicerouter::RequestDispatcherBase<facebook::servicerouter::ThriftDispatcher>::prepareForSelection(facebook::servicerouter::DispatchContext&)::{lambda(folly::fibers::Promise<facebook::servicerouter::RequestDispatcherBase<facebook::servicerouter::ThriftDispatcher>::prepareForSelection(facebook::servicerouter::DispatchContext&)::SelectionResult>)#1},
>>>>>>>>> void>::type::value_type
>>>>>>>>> folly::fibers::await<facebook::servicerouter::RequestDispatcherBase<facebook::servicerouter::ThriftDispatcher>::prepareForSelection(facebook::servicerouter::DispatchContext&)::{lambda(folly::fibers::Promise<facebook::servicerouter::RequestDispatcherBase<facebook::servicerouter::ThriftDispatcher>::prepareForSelection(facebook::servicerouter::DispatchContext&)::SelectionResult>)#1}>(folly::fibers::FirstArgOf&&)::{lambda()#1}>(folly::fibers::FiberManager&,
>>>>>>>>>
>>>>>>>>> folly::fibers::FirstArgOf<folly::fibers::FirstArgOf<facebook::servicerouter::RequestDispatcherBase<facebook::servicerouter::ThriftDispatcher>::prepareForSelection(facebook::servicerouter::DispatchContext&)::{lambda(folly::fibers::Promise<facebook::servicerouter::RequestDispatcherBase<facebook::servicerouter::ThriftDispatcher>::prepareForSelection(facebook::servicerouter::DispatchContext&)::SelectionResult>)#1},
>>>>>>>>> void>::type::value_type
>>>>>>>>> folly::fibers::await<facebook::servicerouter::RequestDispatcherBase<facebook::servicerouter::ThriftDispatcher>::prepareForSelection(facebook::servicerouter::DispatchContext&)::{lambda(folly::fibers::Promise<facebook::servicerouter::RequestDispatcherBase<facebook::servicerouter::ThriftDispatcher>::prepareForSelection(facebook::servicerouter::DispatchContext&)::SelectionResult>)#1}>(folly::fibers::FirstArgOf&&)::{lambda()#1},
>>>>>>>>> void>::type::value_type)::{lambda(folly::fibers::Fiber&)#1}*>()
>>>>>>>>> const+25>
>>>>>>>>> "\311\303UH\211\345H\211}\370H\213E\370]ÐUH\211\345H\203\354\020H\211}\370H\213E\370H\211\307\350~\264\312\377\220\311\303UH\211\345SH\203\354\030H\211}\350H\211u\340H\213E\340H\211\307\350\236\377\377\377H\213\030H\213E\350H\211\307\350O\264\312\377H\211ƿ\b",
>>>>>>>>> size_ = 0,
>>>>>>>>> capacity_ = 1441151880758558720}}}}
>>>>>>>>>
>>>>>>>>> Utf-16 does not seem to decode it, while 'latin-1' does:
>>>>>>>>>>>> '\xc9'.decode('utf-16')
>>>>>>>>> Traceback (most recent call last):
>>>>>>>>> File "<stdin>", line 1, in <module>
>>>>>>>>> File
>>>>>>>>> "/mnt/gvfs/third-party2/python/55c1fd79d91c77c95932db31a4769919611c12bb/2.7.8/centos6-native/da39a3e/lib/python2.7/encodings/utf_16.py",
>>>>>>>>> line 16, in decode
>>>>>>>>> return codecs.utf_16_decode(input, errors, True)
>>>>>>>>> UnicodeDecodeError: 'utf16' codec can't decode byte 0xc9 in position
>>>>>>>>> 0: truncated data
>>>>>>>>>>>> '\xc9'.decode('latin-1')
>>>>>>>>> u'\xc9'
>>>>>>>>>
>>>>>>>>> Instead of guessing what kind of decoding I should use, I would use
>>>>>>>>> 'ensure_ascii=False' to prevent the crash for now.
>>>>>>>>>
>>>>>>>>> I tried to reproduce this crash, but it seems that the crash might be
>>>>>>>>> related with some internal stl implementation we are using. I will
>>>>>>>>> see if I can narrow down to a small repro later.
>>>>>>>>>
>>>>>>>>> Thanks
>>>>>>>>> Jeffrey
>>>>>>>>>
>>>>>>>>> On Sun, Mar 27, 2016 at 2:49 PM, Siva Chandra <sivachan...@gmail.com>
>>>>>>>>> wrote:
>>>>>>>>>> On Sat, Mar 26, 2016 at 11:58 PM, Jeffrey Tan
>>>>>>>>>> <jeffrey.fu...@gmail.com> wrote:
>>>>>>>>>> Btw: after patching with Siva's fix http://reviews.llvm.org/D18008,
>>>>>>>>>> the
>>>>>>>>>> first field 'small_' is fixed, however the second field 'ml_' still
>>>>>>>>>> emits
>>>>>>>>>> garbage:
>>>>>>>>>>
>>>>>>>>>> (lldb) fr v corpus
>>>>>>>>>> (const string &const) corpus = error: summary string parsing error: {
>>>>>>>>>> store_ = {
>>>>>>>>>> = {
>>>>>>>>>> small_ = "www"
>>>>>>>>>> ml_ = (data_ =
>>>>>>>>>> "��UH\x89�H�}�H\x8bE�]ÐUH\x89�H��H\x89}�H\x8bE�H\x89��~\xb4��\x90��UH\x89�SH\x83�H\x89}�H�u�H�E�H���\x9e���H\x8b\x18H\x8bE�H���O\xb4��H\x89ƿ\b",
>>>>>>>>>> size_ = 0, capacity_ = 1441151880758558720)
>>>>>>>>>> }
>>>>>>>>>> }
>>>>>>>>>> }
>>>>>>>>>
>>>>>>>>> Do you still see the DW_TAG_member related error?
>>>>>>>>>
>>>>>>>>> A wild (and really wild at that) guess: Is it utf16 data that is being
>>>>>>>>> decoded as utf8?
>>>>>>>>>
>>>>>>>>> As David Blaikie mentioned on the other thread, it would really help
>>>>>>>>> if you provide us with a minimal example to repro this. Atleast, repro
>>>>>>>>> instructions.
>>>>>>>>>
>>>>>>>>> _______________________________________________
>>>>>>>>> lldb-dev mailing list
>>>>>>>>> lldb-dev@lists.llvm.org
>>>>>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
>>>>>>>>
>>>>>>>> _______________________________________________
>>>>>>>> lldb-dev mailing list
>>>>>>>> lldb-dev@lists.llvm.org
>>>>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
>>>>>>>
>>>>>>>
>>>>>>> Thanks,
>>>>>>> - Enrico
>>>>>>> 📩 egranata@.com ☎️ 27683
>>>>>
>>>>>
>>>>>
>>>>> Thanks,
>>>>> - Enrico
>>>>> 📩 egranata@.com ☎️ 27683
>>>
>>>
>>>
>>> Thanks,
>>> - Enrico
>>> 📩 egranata@.com ☎️ 27683
>
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