ChuanqiXu added a comment. In D139168#4026799 <https://reviews.llvm.org/D139168#4026799>, @ben.boeckel wrote:
> In D139168#4025277 <https://reviews.llvm.org/D139168#4025277>, @ChuanqiXu > wrote: > >> Currently we will detect `-MF` in the command line and we will write the >> make-format dependency output to the corresponding file once we find `-MF`. > > Which is fine, but docs need to mention that some clang-looking flags are > actually for `clang-scan-deps` and that, as such, these flags cannot just be > grabbed blindly from a compilation database. Sure, agreed. I'll add docs for the series patches once they got accepted (otherwise we might do many useless works). > When using clang-scan-deps with a compdb with multiple command lines, which > depfile path will it use? Or must all agree on the same path and options? > Because there should be a single one for all scanning that is performed > (e.g., in batch mode). Currently, clang-scan-deps won't check for this. If we have multiple command lines with different `-MF` value, the make-style dependency information will be written to these different depfiles. If all the command lines use the same depfile, then the make-style dependency information will be written to the depfile. (BTW, We have a lock for this so we don't need to worry about data racing). > Is this really simpler than just adding -MF and friends to clang-scan-deps > directly? Personally, I feel the complexity of both methods are acceptable. I rewrite the patch since it looks like @jansvoboda11 don't like to add new command line options to clang-scan-deps. I feel like we have 2 (or 3) options 1. (The current way) Extract `-MF` in the command line of clang (from compilation database or from the args after `--`) 2. (The original way) Specify `-MF` in the command line of clang-scan-deps. 3. (Not good) Do nothing. I feel like it is possible for build systems to get the make-style dependency information by scanning twice. One for P1689 <https://reviews.llvm.org/P1689> format and one for make-format. It may be workable but it sounds a little bit silly. Personally, I feel the first (current) style is cleaner. > I'll note that I'm becoming more and more convinced that > `compilation_database.json` is being abused for this as we are quite > contorting it from its intended use case: listing the command lines to > compile sources. Instead, we are using it as a source of *related* > information that differs from the *real* command line in some important ways. > Namely: > > - dependency information extraction is re-used and therefore must be > different from the *real* command > - module information must be missing from the scanning command line as it > cannot be known at this point as scanning is used to discover those flags in > the first place (usually a response file) Agreed. But this may beyond the scope of the current patch. 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
