[lldb-dev] How to deal with STL type names in C++ code?

[Enrico Granata via lldb-dev]

> On Aug 6, 2015, at 3:33 PM, Siva Chandra <sivachandra at google.com> wrote:
> 
> 
> 
> On Thu, Aug 6, 2015 at 2:43 PM, Enrico Granata <egranata at apple.com <mailto:egranata at apple.com>> wrote:
> To be honest, my favorite approach would be to modify clang’s TypePrinter to do this, and then hooking up GetDisplayTypeName() to use whatever flags would be necessary to invoke that bit of magic
> 
> Do you mean that clang's "pretty printer" should be made extensible by a script?
>  

Nope, what I am imagining is not an extensible system

When LLDB goes to print a type it asks the compiler “what is the name of this type that I should display?”
By default, clang prints the fully specialized template, including type arguments that have their default value. My theory is that we would want to add a mode to the type printer to say “simplify type name”, and that would do sensible things to get a display name that is more compact

That seems more interesting than a set of regular expression heuristics on the type name, which is probably all you could do without specialized compiler-y knowledge of types

> 
>> On Aug 6, 2015, at 2:33 PM, Siva Chandra <sivachandra at google.com <mailto:sivachandra at google.com>> wrote:
>> 
>> FWIW, GDB has a similar concept called type-printers:
>> https://sourceware.org/gdb/current/onlinedocs/gdb/Type-Printing-API.html <https://sourceware.org/gdb/current/onlinedocs/gdb/Type-Printing-API.html>
>> 
>> On Thu, Aug 6, 2015 at 2:24 PM, Siva Chandra <sivachandra at google.com <mailto:sivachandra at google.com>> wrote:
>>> Hi Enrico,
>>> 
>>> I was thinking about the same issue today. Could we add a concept
>>> called "TypeNameModifier" and provide ability to define modifiers in
>>> scripts and command line? With this, a name like
>>> std::__1::basic_string<...> can be modified into a more friendly name
>>> like std::string? We could ofcourse have more complex modifications.
>>> 
>>> I think it is doable, but what is your (and the community's) opinion
>>> about adding such a feature? If you are OK, I would like to take up
>>> adding such a feature.
>>> 
>>> Thanks,
>>> Siva Chandra
>>> 
>>> On Thu, Aug 6, 2015 at 2:15 PM, Enrico Granata via lldb-dev
>>> <lldb-dev at lists.llvm.org <mailto:lldb-dev at lists.llvm.org>> wrote:
>>>> Hi Eugene,
>>>> 
>>>> On Aug 6, 2015, at 2:02 PM, Eugene Birukov via lldb-dev
>>>> <lldb-dev at lists.llvm.org <mailto:lldb-dev at lists.llvm.org>> wrote:
>>>> 
>>>> Hi,
>>>> 
>>>> I am using LLDB C++ API to create custom debugger and trying to dump
>>>> variables with their types. To do that I am using SBValue.GetTypeName() API.
>>>> Some types are OK, but some others - especially ones related to STL - are
>>>> quite unreadable:
>>>> 
>>>> 
>>>> those type names are the actual fully-specialized STL type names. I am not
>>>> sure how to control GDB to stop truncating your string formatting, but after
>>>> the “…” there actually is more text
>>>> It looks like what you have is std::unique_ptr<std::vector<std::string> > >
>>>> and those templates all take more arguments which are defaulted so you don’t
>>>> have to type them in code - but are reflected in the type name
>>>> 
>>>> (gdb) p value.GetTypeName()
>>>> $1 = 0x7fffe419be40
>>>> "std::__1::unique_ptr<std::__1::vector<std::__1::basic_string<char,
>>>> std::__1::char_traits<char>, std::__1::allocator<char> >,
>>>> std::__1::allocator<std::__1::basic_string<char,
>>>> std::__1::char_traits<char"...
>>>> (gdb) p value.GetDisplayTypeName()
>>>> $2 = 0x7fffe419be40
>>>> "std::__1::unique_ptr<std::__1::vector<std::__1::basic_string<char,
>>>> std::__1::char_traits<char>, std::__1::allocator<char> >,
>>>> std::__1::allocator<std::__1::basic_string<char,
>>>> std::__1::char_traits<char"...
>>>> (gdb)
>>>> 
>>>> 
>>>> So, is there any way to convert them into some more human-friendly form?
>>>> 
>>>> 
>>>> Not currently. What one would have to do is hook into the C++ type printing
>>>> logic such that it would know to leave out these extra template arguments
>>>> when they have a default value
>>>> 
>>>> 
>>>> Thanks,
>>>> Eugene
>>>> _______________________________________________
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>>>> lldb-dev at lists.llvm.org <mailto:lldb-dev at lists.llvm.org>
>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev <http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev>
>>>> 
>>>> 
>>>> 
>>>> Thanks,
>>>> - Enrico
>>>> 📩 egranata@.com ️ 27683
>>>> 
>>>> 
>>>> _______________________________________________
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>>>> 
> 
> 
> Thanks,
> - Enrico
> 📩 egranata@.com ☎️ 27683
> 
> 


Thanks,
- Enrico
📩 egranata@.com ☎️ 27683

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