[PATCH] D113880: [clang][modules] Infer framework modules in explicit builds

[Jan Svoboda via Phabricator via cfe-commits]

jansvoboda11 created this revision.
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When the dependency scanner discovers dependency on an inferred module, it correctly reports the original modulemap path (instead of the virtual `__inferred_module.map` file) as the input file for building the module.

However, during explicit build, `-fimplicit-module-maps` is necessary to successfully build such module. Without the flag, the module is not inferred:

  // HeaderSearch.cpp:1681
    case LMM_InvalidModuleMap:
      // Try to infer a module map from the framework directory.
      if (HSOpts->ImplicitModuleMaps)
        ModMap.inferFrameworkModule(Dir, IsSystem, /*Parent=*/nullptr);
      break;

... and the build fails with "unknown module" error.

To support explicit builds of inferred modules, D102495 <https://reviews.llvm.org/D102495> stopped removing the `-fimplicit-module-maps` from the command lines produced by dependency scanner.

While this works, implicit module maps don't seem like a good fit for explicit modules: since the module map necessary to build a module is already known, we don't need to discover `.modulemap` files in search paths.

Besides the possibility of performing unnecessary filesystem operations, `-fimplicit-module-maps` can uncover different semantics between explicit and implicit modules: D113775 <https://reviews.llvm.org/D113775>.

This patch tries attempts to infer modules even in explicit builds if possible, which also enables the dependency scanner to always disable the implicit module maps feature.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D113880

Files:
  clang/include/clang/Lex/ModuleMap.h
  clang/lib/Frontend/FrontendAction.cpp
  clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
  clang/test/ClangScanDeps/modules-full.cpp
  clang/test/ClangScanDeps/modules-inferred.m
  clang/test/ClangScanDeps/modules-pch.c
  clang/test/Modules/explicit-build-inferred.cpp

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