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When objects are imported for modules, there is a chance that a name collision will cause an ODR violation. Previously, only a small number of such violations were detected. This patch provides a stronger check based on AST nodes. The information needed to uniquely identify an object is taked from the AST and put into a one-dimensional byte stream. This stream is then hashed to give a value to represent the object, which is stored with the other object data in the module. When modules are loaded, and Decl's are merged, the hash values of the two Decl's are compared. Only Decl's with matched hash values will be merged. Mismatch hashes will generate a module error, and if possible, point to the first difference between the two objects. The transform from AST to byte stream is a modified depth first algorithm. Due to references between some AST nodes, a pure depth first algorithm could generate loops. For Stmt nodes, a straight depth first processing occurs. For Type and Decl nodes, they are replaced with an index number and only on first visit will these nodes be processed. As an optimization, boolean values are saved and stored together in reverse order at the end of the byte stream to lower the ammount of data that needs to be hashed. Compile time impact was measured at 1.5-2.0% during module building, and negligible during builds without module building. Differential Revision: https://reviews.llvm.org/D21675 llvm-svn: 293585
//===----------------------------------------------------------------------===// // C Language Family Front-end //===----------------------------------------------------------------------===// Welcome to Clang. This is a compiler front-end for the C family of languages (C, C++, Objective-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 web sites. Here are some pointers: Information on Clang: http://clang.llvm.org/ Building and using Clang: http://clang.llvm.org/get_started.html Clang Static Analyzer: http://clang-analyzer.llvm.org/ Information on the LLVM project: http://llvm.org/ If you have questions or comments about Clang, a great place to discuss them is on the Clang development mailing list: http://lists.llvm.org/mailman/listinfo/cfe-dev If you find a bug in Clang, please file it in the LLVM bug tracker: http://llvm.org/bugs/