forked from OSchip/llvm-project
0290c9ca5c
Patch by Rafael Auler! This patch addresses PR15171 and teaches Clang how to call other tools with response files, when the command line exceeds system limits. This is a problem for Windows systems, whose maximum command-line length is 32kb. I introduce the concept of "response file support" for each Tool object. A given Tool may have full support for response files (e.g. MSVC's link.exe) or only support file names inside response files, but no flags (e.g. Apple's ld64, as commented in PR15171), or no support at all (the default case). Therefore, if you implement a toolchain in the clang driver and you want clang to be able to use response files in your tools, you must override a method (getReponseFileSupport()) to tell so. I designed it to support different kinds of tools and internationalisation needs: - VS response files ( UTF-16 ) - GNU tools ( uses system's current code page, windows' legacy intl. support, with escaped backslashes. On unix, fallback to UTF-8 ) - Clang itself ( UTF-16 on windows, UTF-8 on unix ) - ld64 response files ( only a limited file list, UTF-8 on unix ) With this design, I was able to test input file names with spaces and international characters for Windows. When the linker input is large enough, it creates a response file with the correct encoding. On a Mac, to test ld64, I temporarily changed Clang's behavior to always use response files regardless of the command size limit (avoiding using huge command line inputs). I tested clang with the LLVM test suite (compiling benchmarks) and it did fine. Test Plan: A LIT test that tests proper response files support. This is tricky, since, for Unix systems, we need a 2MB response file, otherwise Clang will simply use regular arguments instead of a response file. To do this, my LIT test generate the file on the fly by cloning many -DTEST parameters until we have a 2MB file. I found out that processing 2MB of arguments is pretty slow, it takes 1 minute using my notebook in a debug build, or 10s in a Release build. Therefore, I also added "REQUIRES: long_tests", so it will only run when the user wants to run long tests. In the full discussion in http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20130408/171463.html, Rafael Espindola discusses a proper way to test llvm::sys::argumentsFitWithinSystemLimits(), and, there, Chandler suggests to use 10 times the current system limit (20MB resp file), so we guarantee that the system will always use response file, even if a new linux comes up that can handle a few more bytes of arguments. However, by testing with a 20MB resp file, the test takes long 8 minutes just to perform a silly check to see if the driver will use a response file. I found it to be unreasonable. Thus, I discarded this approach and uses a 2MB response file, which should be enough. Reviewers: asl, rafael, silvas Reviewed By: silvas Subscribers: silvas, rnk, thakis, cfe-commits Differential Revision: http://reviews.llvm.org/D4897 llvm-svn: 217792 |
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| README.txt | ||
README.txt
//===----------------------------------------------------------------------===// // 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.cs.uiuc.edu/mailman/listinfo/cfe-dev If you find a bug in Clang, please file it in the LLVM bug tracker: http://llvm.org/bugs/