<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><br><div><div>On Nov 27, 2012, at 19:28 , Rajendra <<a href="mailto:rks@cse.iitb.ac.in">rks@cse.iitb.ac.in</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">Hi Jordon,<br><br>Are you saying that using visitor methods of RecursiveASTVisitor is not correct way for static analysis of conditions (if-else) and loops (while)? or not recommended?<br></blockquote><div><br></div><div>That's correct. It's the difference between <i>reading</i> your program and <i>running</i> it.</div><div><br></div><br><blockquote type="cite">What about getting control flow information from successors of a basic block for IfStmt, WhileStmt from CFGTerminator? I think this is the way basic blocks in CFG keep information about control flow. Please correct me if this doesn't sound good.<br></blockquote><div><br></div><div>Yes, that's what the CFG is for, and you can use that for flow-sensitive warnings (and we do). However, no path-sensitive information persists; that is, the CFG is perfectly happy to say you can go down both if-conditions here.</div><div><br></div><div>if (x > 1) {</div><div> foo();</div><div>}</div><div>if (x < 0) {</div><div> bar();</div><div>}</div><div><br></div><div>Again, AnalysisBasedWarnings has some very simple logic to do a <i>little</i> of this, but if you actually want to simulate program execution, that's what the static analyzer is for.</div><div><br></div><div>Best,</div><div>Jordan</div><div><br></div><br><blockquote type="cite">On 27-11-2012 11:09 PM, Jordan Rose wrote:<br><blockquote type="cite">Write a static analyzer plugin instead.<br><br>The RecursiveASTVisitor interface is for syntactic checking; it won't<br>be able to do a good job with propagating information forward with,<br>say, loops. If you're looking for a "fast" flow-sensitive analysis,<br>Sema's AnalysisBasedWarnings shows how it's done, but if you want more<br>precision in actually determining which paths are feasible, you're<br>going to need the full power of the static analyzer. You're basically<br>reinventing the entire analyzer core if you're trying to track the<br>flow of data from assignments to conditions and then to which branch<br>is taken.<br><br>Unfortunately, the documentation on how to write a static analyzer<br>"checker" is still a bit limited, but you can find information at<br><a href="http://clang-analyzer.llvm.org/checker_dev_manual.html">http://clang-analyzer.llvm.org/checker_dev_manual.html</a> and the slides<br>from our talk at the LLVM Develeopers' Meeting at<br><a href="http://llvm.org/devmtg/2012-11/Zaks-Rose-Checker24Hours.pdf">http://llvm.org/devmtg/2012-11/Zaks-Rose-Checker24Hours.pdf</a><br><br>Best,<br>Jordan<br><br><br>On Nov 27, 2012, at 1:24 , Rajendra <<a href="mailto:rks@cse.iitb.ac.in">rks@cse.iitb.ac.in</a>> wrote:<br><br><blockquote type="cite">Any suggestion on this topic, please?<br><br>- Rajendra<br><br>On 26-11-2012 03:21 PM, Rajendra wrote:<br><blockquote type="cite">Hi,<br><br>I have overridden VisitIfStmt(Stmt* s) and some visit methods for<br>binary operators:<br>- VisitBinAssign(),<br>- VisitBinAdd() and other arithmetic operators,<br>- VisitBinGT() and other relational operators<br><br>My dilemma is how do I return from different visit methods (or call<br>them explicitly)<br>so that I can perform some analysis on binary operators and use them<br>in condition part,<br>then clause and else clause for IfStmt? e.g. I want to analyze<br>following C program:<br>int main() {<br> int x, y;<br> x = 10;<br> if (x > 0)<br> y = 1;<br> else if (x == 0)<br> y = 0;<br> else<br> y = -1;<br> return 0;<br>}<br><br>Basic block contains:<br> 1: int x;<br> 2: int y;<br> 3: x = 10<br> 4: x > 0<br> T: if [B6.4]<br><br>Now, for condition x > 0 (line 3:) due to VisitBinGT() can get<br>following info:<br> Relational Op ><br> LHS identifier = x<br> type: int<br> RHS value: 0<br>From VisitIfStmt() I can get pointer to condition part, then and else<br>clauses.<br>so, how should I combine IfStmt and information I have due to visit<br>to other methods?<br><br>Please advise.<br><br>- Rajendra<br></blockquote><br>_______________________________________________<br>cfe-dev mailing list<br><a href="mailto:cfe-dev@cs.uiuc.edu">cfe-dev@cs.uiuc.edu</a><br>http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev<br></blockquote></blockquote><br></blockquote></div><br></body></html>