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<p class="MsoNormal">Hello all,<o:p></o:p></p>
<p class="MsoNormal">I’m writing a tool that uses the CFG with different functions.<o:p></o:p></p>
<p class="MsoNormal">I have a problem that when iterating over the elements of a CFGBlock, some of the statements appear twice.<o:p></o:p></p>
<p class="MsoNormal">It is most prevalent in function calls but I saw it in some other cases as well.<o:p></o:p></p>
<p class="MsoNormal">For example, the following code:<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">double i = pow(2.0, 3);
</span><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">will create two elements in the CFGBlock:<o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">[B1]</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> 1: pow(2., 3)</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> 2: double i = pow(2., 3);</span><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">And when I try to reproduce the code from this block (by iterating over the elements and pretty print them), I get two function calls:<o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">pow(2., 3);</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">double i = pow(2., 3);</span><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">I saw the same behavior also in binary operator when the opcode is a comma and in conditional operator.<o:p></o:p></p>
<p class="MsoNormal">Here are some examples:<o:p></o:p></p>
<p class="MsoNormal">1)<o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">int i, k = 10;</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">for (i = 0; i < 10; i++, k--){</span><o:p></o:p></p>
<p class="MsoNormal" style="text-indent:.5in"><span style="font-family:"Courier New"">// some code</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">}</span><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">The block that corresponds to the step of the for loop looks like that:<o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">[B2]</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> 1: i++</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> 2: k--</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> 3: [B2.1], [B2.2]</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> </span><o:p></o:p></p>
<p class="MsoNormal">Which creates the code:<o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">i++;</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">k--;</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">i++, k--;</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> </span><o:p></o:p></p>
<p class="MsoNormal">2)<o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">return a > 0? a : -a;</span><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Creates this block:<o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">1: [B4.2] ? [B2.1] : [B3.1]</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> 2: return [B1.1];</span><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Which pretty prints the following code:<o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">a > 0 ? a : -a;</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">return a > 0 ? a : -a;</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> </span><o:p></o:p></p>
<p class="MsoNormal">I suspect that the reason for this behavior is that the CFG is built recursively and some of the statements are visited and appended twice to the block.<o:p></o:p></p>
<p class="MsoNormal">In the case of the binary operator with comma, I solved this problem by removing the call to appendStmt in the code below (Which is in CFGBuilder::VisitBinaryOperator() in CFG.cpp file)<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">if (B->getOpcode() == BO_Comma) { // ,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> autoCreateBlock();</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> //appendStmt(Block, B);</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> addStmt(B->getRHS());</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> return addStmt(B->getLHS());</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> }</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> </span><o:p></o:p></p>
<p class="MsoNormal">I tried to solve the problem also by changing VisitCallExpr() and VisitConditioalOperator() but couldn’t solve it there.<o:p></o:p></p>
<p class="MsoNormal">I would appreciate any help and insights about this issue.<o:p></o:p></p>
<p class="MsoNormal">Thanks,<o:p></o:p></p>
<p class="MsoNormal">Rachel. <o:p></o:p></p>
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