On Apr 3, 2014, at 7:49 PM, Richard Smith <[email protected]> wrote:
> On Thu, Apr 3, 2014 at 3:40 PM, Ben Langmuir <[email protected]> wrote: > > On Mar 28, 2014, at 2:45 PM, Richard Smith <[email protected]> wrote: > >> On Fri, Mar 28, 2014 at 1:12 PM, Ben Langmuir <[email protected]> wrote: >> This patch allows multiple modules that have the same name to coexist in the >> module cache. To differentiate between two modules with the same name, we >> will consider the path the module map file that they are defined by* part of >> the ‘key’ for looking up the precompiled module (pcm file). Specifically, >> this patch renames the precompiled module (pcm) files from >> >> cache-path/<module hash>/Foo.pcm >> >> to >> >> cache-path/<module hash>/Foo-<hash of module map path>.pcm >> >> From a high level, I don't really see why we need a second hash here. >> Shouldn't the -I options be included in the <module hash>? If I build the >> same module with different -I flags, that should resolve to different .pcm >> files, regardless of whether it makes the module name resolve to a different >> module.map file. >> >> Are you trying to cope with the case where the -I path finds multiple >> module.map files defining the same module (where it's basically chance which >> one will get built and used)? I don't really feel like this is the right >> solution to that problem either -- we should remove the 'luck' aspect and >> use some sane mechanism to determine which module.map files are loaded, and >> in what order. >> >> Is this addressing some other case? >> >> >> In addition, I’ve taught the ASTReader to re-resolve the names of imported >> modules during module loading so that if the header search context changes >> between when a module was originally built and when it is loaded we can >> rebuild it if necessary. For example, if module A imports module B >> >> first time: >> clang -I /path/to/A -I /path/to/B … >> >> second time: >> clang -I /path/to/A -I /different/path/to/B … >> >> will now rebuild A as expected. >> >> >> * in the case of inferred modules, we use the module map file that *allowed* >> the inference, not the __inferred_module.map file, since the inferred file >> path is the same for every inferred module. >> >> >> Review comments on the patch itself: >> >> + /// the inferrence (e.g. contained 'module *') rather than the virtual >> >> Typo 'inference', 'Module *'. >> >> + /// For an explanaition of \p ModuleMap, see Module::ModuleMap. >> >> Typo 'explanation'. >> >> + // safe becuase the FileManager is shared between the compiler instances. >> >> Typo 'because' >> >> + // the inferred module. If this->ModuleMap is nullptr, then we are using >> + // -emit-module directly, and we cannot have an inferred module. >> >> I don't understand what this comment is trying to say. If we're using >> -emit-module, then we were given a module map on the command-line; should >> that not be referred to by this->ModuleMap? (Also, why 'this->'?) How can a >> top-level module be inferred? Is that a framework-specific thing? >> >> + StringRef ModuleMap = this->ModuleMap ? this->ModuleMap->getName() : >> InFile; >> >> Please pick a different variable name rather than shadowing a member of >> '*this' here. >> >> + // Construct the name <ModuleName>-<hash of ModuleMapPath>.pcm which >> should >> + // be globally unique to this particular module. >> + llvm::APInt Code(64, llvm::hash_value(ModuleMapPath)); >> + SmallString<128> HashStr; >> + Code.toStringUnsigned(HashStr); >> >> Use base 36, like the module hash. > > > I’ve attached an updated patch. Changes since the previous one: > 1. Fixed the typos and other issues Richard pointed out > 2. I’ve added code to canonicalize the module map path (using realpath); I > was getting spurious failures on case-intensitive filesystems. > > This part is probably not OK, because it'll do the wrong thing on some build > farms (where the canonical path is not predictable, but the path that > make_absolute returns is, by careful control of $PWD). I'll look into this > more, but will be traveling for the next couple of days. Okay, I have a better idea: I already store the actual module map path in MODULE_MAP_FILE, so when that is read, we can just get a FileEntry for it and compare to what header search finds for the current module (since FileEntries are uniqued by inode). That also means I can give a better diagnostic with the module map paths rather than the pcm filenames. > > 3. I’ve moved the initialization of the MainFileID (in source manager) from > Execute() to BeginSourceFile(), since we are now potentially creating file > ids for module map files during pch loading and need to be able to find the > main file reliably to construct a correct include stack.
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