Zoltán Borók-Nagy, Viktor Májer, József Mihalicza, Norbert Pataki, … · 2019-11-08 · Introduction Templight Debugger Visualizer Conclusion Visualization of C++ Template Metaprograms1

Introduction Templight Debugger Visualizer Conclusion

Visualization of C++ Template Metaprograms1

Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Dept. Programming Languages and CompilersEötvös Loránd University, Budapest, Hungary

SCAM 2010

1TÁMOP-4.2.1/B-09/1/KMR-2010-0003Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Contents

1 Introduction

2 Templight

3 Debugger

4 Visualizer

5 Conclusion

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

C++ Templates

Different from Java / C# genericsJava / C#: type erasureC++: instantitation

Mainly used for libraries: STL, etc.Templates are skeletons, code generated on demandPossibility for specialisationRecursive templates are ok

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

C++ Template Metaprogram - example

template <int N>struct Factorial{enum { Value = N * Factorial<N-1>::Value};

};template <>struct Factorial<0>{enum { Value = 1 };

};

int main(){std::cout << Factorial<5>::Value;

}

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

C++ Template Metaprogram features

Executed at compilation-timeFunctional paradigmWhy we used them:

optimalizations of runtime programs, expression templatesstatic interface checking, concept checkingcompile-time code adoption, active librariesembedding DSLs

Turing complete

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Motivation

Metaprogramming is side effect of template constructTemplate syntax is not helpfulCompiler interprets metaprograms at compilation-timeNo user input, trivial printouts, etc.Maintenance is hopeless

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Motivation

Metaprogramming is side effect of template constructTemplate syntax is not helpfulCompiler interprets metaprograms at compilation-timeNo user input, trivial printouts, etc.Maintenance is hopeless

C++ template metaprogram code comprehension tools areessential

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Templight

Lightweight parser using boost wave and spiritInstruments template classes/functions injecting begin/endmarkersMarkers emit compilation warnings on instantiationCollects warnings generating a "stack-trace"Post-mortem wayTake advantage of compiler dependent implementationdetails (e.g. memoization)

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Debugger

Based on TemplightGUI is based on QTImplements "usual" debugger features:

Breakpoints, continueStep in/out/overLocals, watch

Backward execution

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Screenshot

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Visualizer

Based on TemplightTransform the instantiation chain into a directed graph:

nodes: types generated from templatesedges show the instantiation requests

Show corresponding codeFilter out irrevelant nodesExport to png, jpg etc,

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Unruh Example Demonstration

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Unruh Example Demonstration

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Unruh Example Demonstration

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Unruh Example Demonstration

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Unruh Example Demonstration

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Unruh Example Demonstration

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Unruh Example Demonstration

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Unruh Example Demonstration

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Unruh Example Demonstration

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Unruh Example Demonstration

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Unruh Example Demonstration

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Conclusion

It is hard to understand and maintain C++ templatemetaprogramsVisualization of programs is essentialWe have created a basic framework called TemplightWe have developed a graphical user interfacedpost-mortem debuggerWe have implemented a tool to visualize the C++ templatemetaprograms as graphs

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Controversial

template <int p, int i>struct is_prime {enum {prim = (p==2) ||

(p%i) &&is_prime<(i>2?p:0),i-1>::prim

};};template<>struct is_prime<0,0> {enum {prim=1};

};template<>struct is_prime<0,1> {enum {prim=1};

};Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Controversial

C++ source is the assembly of template metaprogram.

We have to use high level functional programming languages,like Haskell, to write metaprograms, and generate C++ source.

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb

Introduction Templight Debugger Visualizer Conclusion

Controversial

C++ source is the assembly of template metaprogram.

We have to use high level functional programming languages,like Haskell, to write metaprograms, and generate C++ source.

Thank you for attention

Visualization of C++ Template Metaprograms Zoltán Borók-Nagy, Viktor Májer, József Mihalicza,Norbert Pataki, Zoltán Porkoláb