ChuanqiXu added a comment. In D139168#4036850 <https://reviews.llvm.org/D139168#4036850>, @tahonermann wrote:
>> Header units have even more need to be involved in the build graph than >> named units. ODR violations and cache invalidation problems await anyone >> just winging it on header units (at least that's the understanding I've >> gotten from SG15 meetings). > > I think that latter claim applies equally to all module units. The ODR > violation and cache invalidation concerns sometimes associated with header > units occur in implicit module build systems in which a header unit might be > built multiple times with different sets of options that result in an ODR > violation. The same problem can occur with other kinds of module units if > they are built multiple times with different options and then imported by > distinct TUs that are then linked together. The general rule is, given a set > of TUs that will be linked together, all imported module units should be > built exactly one time. I think the option set will be naturally a unique set for a single module-unit since a module-unit is an actual translation unit. But the header units are synthesized units so it is not the same case. I am pretty interested about the topic indeed but I guess we'd better to find another place to discuss this. ================ Comment at: clang/tools/clang-scan-deps/ClangScanDeps.cpp:775 + static llvm::StringMap<llvm::raw_fd_ostream> OSs; + std::unique_lock<std::mutex> LockGuard(Lock); + ---------------- jansvoboda11 wrote: > How will this work when a different process tries to write the same file? > Could we write into a temporary file and then do atomic rename? It may be problematic if another process tries to write the same file at the same time. But I feel it is an overkill to defend such cases otherwise many existing codes need to be refactored. CHANGES SINCE LAST ACTION https://reviews.llvm.org/D139168/new/ https://reviews.llvm.org/D139168 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
