en Copyright 2015 Java http://172.16.0.5:8080/history/llvm-project-15.0.7/clang/test/Modules/preprocess-missing.modulemap#040e1266 Support lazy stat'ing of files referenced by module maps.This patch adds support for a `header` declaration in a module map to specifycertain `stat` information (currently, size and mtime) about that header file.This has two purposes:- It removes the need to eagerly `stat` every file referenced by a module map. Instead, we track a list of unresolved header files with each size / mtime (actually, for simplicity, we track submodules with such headers), and when attempting to look up a header file based on a `FileEntry`, we check if there are any unresolved header directives with that `FileEntry`'s size / mtime and perform deferred `stat`s if so.- It permits a preprocessed module to be compiled without the original files being present on disk. The only reason we used to need those files was to get the `stat` information in order to do header -> module lookups when using the module. If we're provided with the `stat` information in the preprocessed module, we can avoid requiring the files to exist.Unlike most `header` directives, if a `header` directive with `stat`information has no corresponding on-disk file the enclosing module is *not*marked unavailable (so that behavior is consistent regardless of whether we'veresolved a header directive, and so that preprocessed modules don't get markedunavailable). We could actually do this for all `header` directives: the onlyreason we mark the module unavailable if headers are missing is to give adiagnostic slightly earlier (rather than waiting until we actually try to buildthe module / load and validate its .pcm file).Differential Revision: https://reviews.llvm.org/D33703llvm-svn: 304515 List of files: /llvm-project-15.0.7/clang/test/Modules/preprocess-missing.modulemap Fri, 02 Jun 2017 01:55:39 +0000 Richard Smith <richard-llvm@metafoo.co.uk>