<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hi Guoping,<div><br></div><div>I thought that you saw an assertion failure by running $ clang --analyze. I did not realize that you are running custom code to build up the UninitializedVariables. I am not familiar enough with that code to know what's wrong without debugging it.</div><div><br></div><div>Most likely there is some issue with the way you build the analysis in your code; you should probably look at other uses of UninitializedVariables to see what you are missing. Also, try to find out at which step the first symptoms of the problem occur - for example, do you get a CFG different from what you see when dumping the CFG with a debug checker? (See the command from Ted's reply below.)</div><div><br></div><div>I noticed that you do not pass CFGBuildOptions when constructing the <span class="Apple-style-span" style="font-family: Menlo; font-size: 11px; ">AnalysisContext. </span>Here is some code from AnalysisBasedWarnings.cpp, which implies that you might need to request linearized CFG.</div><div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 11px/normal Monaco; color: rgb(77, 144, 114); "><span style="color: rgb(0, 0, 0); "> </span>// Unreachable code analysis requires a linearized CFG.</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 11px/normal Monaco; "> AC.getCFGBuildOptions().setAllAlwaysAdd();</div></div><div><br></div><div>Also, what are you trying to do? Maybe just writing a checker would be a simpler solution.</div><div><br></div><div>Hope this helps,</div><div>Anna.</div><div><div>On Oct 9, 2011, at 5:32 PM, Guoping Long wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">Hi, Anna<div><br></div><div> Here are steps on how I got this error:</div><div>1 Get the latest code:</div><div> A. <span class="Apple-style-span" style="font-family: monospace; line-height: 15px; background-color: rgb(255, 255, 255); ">svn co <a href="http://llvm.org/svn/llvm-project/llvm/trunk">http://llvm.org/svn/llvm-project/llvm/trunk</a> llvm</span></div>
<div> B. <span class="Apple-style-span" style="font-family: monospace; line-height: 15px; background-color: rgb(255, 255, 255); ">svn co <a href="http://llvm.org/svn/llvm-project/cfe/trunk">http://llvm.org/svn/llvm-project/cfe/trunk</a> clang</span></div>
<div>2. Configure & Make</div><div> A. make a separate directory for build: makedir llvm-build</div><div> B. In llvm-build/, using cmake to generate the Makefile:</div><div> cmake ../llvm -DCMAKE_BUILD_TYPE=Debug</div>
<div> C. make & make install</div><div>3. Add a test:</div><div> A. create a directory: tools/clang/examples/Debug</div><div> B. write a test file, as attached.</div><div> C. Modify tools/clang/CMakeLists.txt to build the examples/ directory. </div>
<div> D. Add CMakeLists.txt in tools/clang/examples/Debug to build the newly added test program.</div><div> E. when the program is built, run it with the previous test program to get this error.</div><div><br></div>
<div>I am using MacOS 10.6.8, x86-64 Intel platform.</div><div>It seems my source tree is not in the right configuration? Please let me know what's wrong in my environment. I will be deeply appreciated. Thanks.</div><div>
<br></div><div>-------</div><div>Guoping<br><br><div class="gmail_quote">2011/10/9 Anna Zaks <span dir="ltr"><<a href="mailto:ganna@apple.com">ganna@apple.com</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div style="word-wrap:break-word">Hi Guoping,<div><br></div><div>I cannot reproduce the assertion failure.</div><div><br></div><div>Is it still reproducible with the latest revision of Clang/LLVM? If yes, can you send the command line you used.</div>
<div><br></div><div>Thanks,</div><div>Anna.</div><div><div></div><div class="h5"><div><br></div><div><div><div>On Oct 9, 2011, at 10:23 AM, Guoping Long wrote:</div><br><blockquote type="cite">Also, it seems there is an assert error in UninitializedValues.cpp. Giving this test program:<div>
<div> 1 int main(int argc, char *argv[])</div><div> 2 {</div><div> 3 int x=3, y = 5, z = 6;</div><div> 4 </div><div> 5 if(x<0) {</div>
<div> 6 while(y>0){</div><div> 7 y--;</div><div> 8 x = z+1;</div><div> 9 }</div><div> 10 }else x = y;</div><div> 11 return 0;</div><div> 12 }</div><div>Here is the assert error: </div><div>
<div>
Assertion failed: (res.getDeclRefExpr() == lastDR), function VisitUnaryOperator, file /Users/gplong/llvm/tools/clang/lib/Analysis/UninitializedValues.cpp, line 529.</div></div><div>This message is triggered in call VisitUnaryOperator(). The line number may not be correct because I added some print statements.</div>
<div><br></div><div>-----</div><div>Guoping</div><br><div class="gmail_quote">2011/10/8 Guoping Long <span dir="ltr"><<a href="mailto:longguoping@gmail.com" target="_blank">longguoping@gmail.com</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
On my testing environment, the UninitializedValues.cpp has the same problem (do not have any output). Both analyses are based on the StmtVisitor interface. I think there may be a version mismatch, that is these two analyses are based on an older version of StmtVisitor class to work? I just downloaded a new version from website and did all tests again and still have this problem.<div>
<br></div><div>----</div><div>Guoping<div><div></div><div><br><br><div class="gmail_quote">2011/10/8 Guoping Long <span dir="ltr"><<a href="mailto:longguoping@gmail.com" target="_blank">longguoping@gmail.com</a>></span><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi, Ted<div><br></div><div> I will be very curious why results in your environment are correct. Attached is my test code. I stepped into the program using GDB, it turned out that no live variables can be found. Take the last return statement in my previous example program as an example: return b * d + c. The transfer function eventually called the default StmtVisit function which did not recognize variables b, d, c which are actually used.The only function in LiveVariables.cpp that can generate live variables is VisitDeclRefExpr(), but when running the program this function is never called. </div>
<div><br></div><div> I am using the newest version of Clang/LLVM. Is it because my environment setup is wrong? </div><div><br></div><div>----</div><div>Guoping</div><div><div></div><div><div><br><div class="gmail_quote">
2011/10/7 Ted Kremenek <span dir="ltr"><<a href="mailto:kremenek@apple.com" target="_blank">kremenek@apple.com</a>></span><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word">This is what I am seeing:<div><br></div><div><div>$ clang -cc1 -analyze -analyzer-checker=debug.DumpLiveVars t.c</div>
<div><br></div><div>[ B0 (live variables at block exit) ]</div><div><br></div><div>[ B1 (live variables at block exit) ]</div><div><br></div><div>[ B2 (live variables at block exit) ]</div><div> b <t.c:2:10></div><div>
d <t.c:2:16></div><div><br></div><div>[ B3 (live variables at block exit) ]</div><div> a <t.c:2:7></div><div> b <t.c:2:10></div><div> d <t.c:2:16></div><div><br></div><div>[ B4 (live variables at block exit) ]</div>
<div><br></div><div><br></div><div>I also think the number of the blocks is not quite right in your example, or at least how they correspond to Clang's CFG:</div><div><br></div><div><div>$ clang -cc1 -analyze -analyzer-checker=debug.DumpCFG t.c</div>
<div><br></div><div> [ B4 (ENTRY) ]</div><div> Predecessors (0):</div><div> Successors (1): B3</div><div><br></div><div> [ B1 ]</div><div> 1: 4</div><div> 2: c</div><div> 3: [B1.2] = [B1.1]</div><div>
4: b</div><div> 5: [B1.4]</div><div> 6: d</div><div> 7: [B1.6]</div><div> 8: [B1.5] * [B1.7]</div><div> 9: c</div><div> 10: [B1.9]</div><div> 11: [B1.8] + [B1.10]</div><div> 12: return [B1.11];</div>
<div> Predecessors (2): B2 B3</div><div> Successors (1): B0</div><div><br></div><div> [ B2 ]</div><div> 1: a</div><div> 2: [B2.1]</div><div> 3: b</div><div> 4: [B2.3]</div><div> 5: [B2.2] + [B2.4]</div>
<div> 6: c</div><div> 7: [B2.6] = [B2.5]</div><div> 8: 2</div><div> 9: d</div><div> 10: [B2.9] = [B2.8]</div><div> Predecessors (1): B3</div><div> Successors (1): B1</div><div><br></div><div>
[ B3 ]</div><div> 1: int a;</div><div> 2: int b;</div><div> 3: int c;</div><div> 4: int d;</div><div> 5: int x;</div><div> 6: 3</div><div> 7: a</div><div> 8: [B3.7] = [B3.6]</div>
<div>
9: 5</div><div> 10: b</div><div> 11: [B3.10] = [B3.9]</div><div> 12: 4</div><div> 13: d</div><div> 14: [B3.13] = [B3.12]</div><div> 15: 100</div><div> 16: x</div><div> 17: [B3.16] = [B3.15]</div>
<div> 18: a</div><div> 19: [B3.18]</div><div> 20: b</div><div> 21: [B3.20]</div><div> 22: [B3.19] > [B3.21]</div><div> T: if [B3.22]</div><div> Predecessors (1): B4</div><div> Successors (2): B2 B1</div>
<div><br></div><div> [ B0 (EXIT) ]</div><div> Predecessors (1): B1</div><div> Successors (0):</div></div><div><br></div><div><br></div><div>Block B3 is actually the entrance block, since the CFG is built bottom-up.</div>
<div><br></div><div>Perhaps there is something not quite right with how you are running the checkers?</div><div><br></div><div><div><div></div><div><div>On Oct 7, 2011, at 9:32 PM, Guoping Long wrote:</div><br>
</div></div><blockquote type="cite"><div><div></div><div>Hi, <div><br></div><div> While LiveVariables analysis (tools/clang/lib/Analysis/LiveVariables.cpp) does not generate any output? Specifically, for this simple program:</div>
<div><div> 1 int main(int argc, char *argv[])</div>
<div> 2 {</div><div> 3 int a,b,c,d,x;</div><div> 4 </div><div> 5 a = 3; //Basic block B1</div><div> 6 b = 5;</div><div> 7 d = 4;</div><div> 8 x = 100;</div><div> 9 </div><div> 10 if(a>b){ //Basic block B2</div>
<div> 11 c = a+b;</div><div> 12 d = 2;</div><div> 13 }</div><div> 14 </div><div> 15 c = 4; //Basic block B3</div><div> 16 return b * d + c;</div><div> 17 }</div></div><div>This simple example is taken from this wiki page illustrating live variables analysis (<a href="http://en.wikipedia.org/wiki/Live_variable_analysis" target="_blank">http://en.wikipedia.org/wiki/Live_variable_analysis</a>).</div>
<div>Both B2 and B3 should have live variables, but the output (using LiveVariables::dumpBlockLiveness(SourceManager &)) says no live variables exist. I am trying to use this analysis as an example on how to write a good analysis algorithm for Clang, but really did not expect this behavior for this analysis.</div>
<div>Anybody who knows the answer please let me know. Many thanks!!!</div><div><br></div><div>--------</div><div>Guoping</div></div></div>
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