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---++ Architecture

Lightweight program (which we call _filters_) operate on program source files and/or data files and produce data files. The filters can be stacked in pipelines, where each filter in the pipeline reads data files generated by prior filters and in turn generates new data files. The design motivation behind this structure is to allow pipelines of filter programs to be constructed to implement program analysis. This modular design is important to isolate the language-specific first pipeline stages from later language-independent modules and in this way support sophisticated analysis for multilingual condebases.

<img alt="Static_Analysis_diagram.png" height="801" src="%ATTACHURL%/Static_Analysis_diagram.png" title="Static_Analysis_diagram.png" width="1213" />

<img alt="Call_Graph_diagram.png" height="426" src="%ATTACHURL%/Call_Graph_diagram.png" title="Call_Graph_diagram.png" width="1203" />

The process starts with C, Python and JavaScript source code from which separate ASTs (Abstract Syntax Tree) are dumped using Clang-Check (for C files)

<img alt="C_AST.jpeg" height="121" src="%ATTACHURLPATH%/C_AST.jpeg" width="951" />

Figure 1: Portion of a C AST file

the AST module and the file [[https://github.com/Psycojoker/ast2json][ast2json.py]] (for Python files),

<img alt="pythonJSON.png" height="363" src="%ATTACHURL%/pythonJSON.png" title="pythonJSON.png" width="718" />

Figure 2: Portion of a Python AST json file

And [[https://developer.mozilla.org/en-US/docs/Mozilla/Projects/SpiderMonkey/Getting_SpiderMonkey_source_code][SpiderMonkey]] for JavaScript files.

<img alt="jsJSON.png" height="383" src="%ATTACHURL%/jsJSON.png" title="jsJSON.png" width="712" />

Figure 3: Portion of a JavaScript AST json file

%BLACK%<font face="arial, verdana, sans-serif"><font>The AST files have very different structures for C, Python and Javascript, but the parsers are designed to handle each kind of AST differently. Those parsers filter the AST files, detecting and recording function calls and their arguments. Initially, the program is capable of detecting literals and variables as arguments. Reaching Definition Analysis has been implemented for C/C++ programs that call Python programs (but none of the other languages) to handle statically assigned variables as arguments to functions. The current version of the program handles part of the Python.h interface between C and Python. It only analyzes “PyRun_SimpleFile” calls. Other mechanisms for calling Python from C will also be implemented in the future. The version can also handle PyV8 's eval function to call a JavaScript program from Python, and JQuerry's ajaz function to call a Python program from JavaScript. In the future, the program will be able to handle cases in which a JavaScript program is called from a C program, and both JavaScript and Python functions call C programs.</font></font>%ENDCOLOR%

<p align="left">%BLACK%<font face="arial, verdana, sans-serif"><font>When the designated function used to call another program of another language, such as “PyRun_SimpleFile” , JSContext().eval() or $.ajax(), is found, its argument (name of the Python or JavaScript file) is considered a function call and the executable portion of that file is represented as the main function in the original program. That creates the connection between the two files, which allows the subsequent programs to build the call graph.</font></font>%ENDCOLOR%</p> <p align="left">%BLACK%“mergeFunCall.<font face="arial, verdana, sans-serif"><font>py” combines all individual csv files from the list of source files into one. This file is then used as input to “generateDot.py”. This program translates the csv file to a dot file, which represents the csv file as a graph. The Dot program builds the final graph </font></font><font face="arial, verdana, sans-serif"><font>via GraphViz </font></font><font face="arial, verdana, sans-serif"><font>and saves it as a PDF file. Circular nodes represent C </font></font><font face="arial, verdana, sans-serif"><font>programs</font></font><font face="arial, verdana, sans-serif"><font>, </font></font><font face="arial, verdana, sans-serif"><font>r</font></font><font face="arial, verdana, sans-serif"><font>ectangular nodes represent Python </font></font><font face="arial, verdana, sans-serif"><font>programs, and hexagonal nodes represent JavaScript programs. Recursive functions are denoted by dashed nodes. Errors, such as circularity in a system or unidentifiable interoperability, are denoted by double-lined dashed nodes.</font></font>%ENDCOLOR%</p>

<img alt="test6_callgraph.png" height="891" src="%ATTACHURL%/test6_callgraph.png" title="test6_callgraph.png" width="1215" />

Figure 4: Example of a multilingual call graph

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Attachments

Topic attachments
I	Attachment	History	Action	Size	Date	Who	Comment
jpeg	C_AST.jpeg	r1	manage	35.9 K	2016-07-27 - 14:46	DamianLyons
png	Call_Graph_diagram.png	r1	manage	41.1 K	2017-04-11 - 15:28	MaggieGates
jpeg	PY_AST.jpeg	r1	manage	19.1 K	2016-07-27 - 14:46	DamianLyons
png	Static_Analysis_diagram.png	r1	manage	30.4 K	2017-07-12 - 14:34	AnneMarieBogar
png	call_graph.png	r1	manage	206.5 K	2017-04-07 - 19:36	DamianLyons
png	callgraph.png	r1	manage	39.2 K	2016-07-27 - 14:46	DamianLyons
png	jsJSON.png	r1	manage	25.7 K	2017-04-07 - 19:27	DamianLyons	javascript AST
png	process_diagram.png	r1	manage	43.9 K	2016-07-27 - 14:59	DamianLyons
png	pythonJSON.png	r1	manage	21.0 K	2017-04-07 - 19:25	DamianLyons	python AST
png	test6_callgraph.png	r1	manage	430.2 K	2017-07-11 - 20:45	AnneMarieBogar

Topic revision: r7 - 2017-07-12 - AnneMarieBogar

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