bb27d5e5c6
This commit ensures that if the loop condition is opaque (the analyzer cannot determine whether it's true or false) and there were at least two iterations, then the analyzer doesn't make the unjustified assumption that it can enter yet another iteration. Note that the presence of a loop suggests that the developer thought that two iterations can happen (otherwise an `if` would've been sufficient), but it does not imply that the developer expected three or four iterations -- and in fact there are many false positives where a loop iterates over a two-element (or three-element) data structure, but the analyzer cannot understand the loop condition and blindly assumes that there may be three or more iterations. (In particular, analyzing the FFMPEG project produces 100+ such false positives.) Moreover, this provides some performance improvements in the sense that the analyzer won't waste time on traversing the execution paths with 3 or 4 iterations in a loop (which are very similar to the paths with 2 iterations) and therefore will be able to traverse more branches elsewhere on the `ExplodedGraph`. This logic is disabled if the user enables the widen-loops analyzer option (which is disabled by default), because the "simulate one final iteration after the invalidation" execution path would be suppressed by the "exit the loop if the loop condition is opaque and there were at least two iterations" logic. If we want to support loop widening, we would need to create a follow-up commit which ensures that it "plays nicely" with this logic.
C language Family Front-end
Welcome to Clang.
This is a compiler front-end for the C family of languages (C, C++ and Objective-C) which is built as part of the LLVM compiler infrastructure project.
Unlike many other compiler frontends, Clang is useful for a number of things beyond just compiling code: we intend for Clang to be host to a number of different source-level tools. One example of this is the Clang Static Analyzer.
If you're interested in more (including how to build Clang) it is best to read the relevant websites. Here are some pointers:
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Information on Clang: http://clang.llvm.org/
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Building and using Clang: http://clang.llvm.org/get_started.html
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Clang Static Analyzer: http://clang-analyzer.llvm.org/
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Information on the LLVM project: http://llvm.org/
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If you have questions or comments about Clang, a great place to discuss them is on the Clang forums:
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If you find a bug in Clang, please file it in the LLVM bug tracker: