[PATCH] D22636: Module: retry building modules that were just compiled by the same instance and are are out of date

[Ben Langmuir via cfe-commits]

benlangmuir added a comment.

> Can you point me to the source codes where we use rename to replace the file? I am curious on how this all works out.


This is the same as clang's handling of other output files.  See {{CompilerInstance::createOutputFile}} and {{clearOutputFiles}}.  When we are performing the GenerateModuleAction, the .pcm file will be the output file.

> What I described is a scenario I thought possible that can cause "out-of-date" error:

>  module "B" is out of date and needs to be rebuilt

>  note: imported by module "A"

>  The only invocation of ReadAST that reads a module file and can't handle out-of-date modules, is the path where we just built module "A" and tries to load module "A" (here ModuleLoadCapabilities will be ARR_Missing).


Right, here and in PCH loading (I assume your case doesn't involve a PCH).  I'm concerned about adding this loop, because it removes the guarantee of progress.  We should never need to build a module more than once in the same compilation.  If we have a bug that's causing us to not be able to load a module that we just compiled, I think we need to fix the underlying problem, not just retry the build.


https://reviews.llvm.org/D22636