Reinstate r213348, reverted in r213395, with an additional bug fix and more

thorough tests.

Original commit message:

[modules] Fix macro hiding bug exposed if:

 * A submodule of module A is imported into module B
 * Another submodule of module A that is not imported into B exports a macro
 * Some submodule of module B also exports a definition of the macro, and
   happens to be the first submodule of B that imports module A.

In this case, we would incorrectly determine that A's macro redefines B's
macro, and so we don't need to re-export B's macro at all.

This happens with the 'assert' macro in an LLVM self-host. =(

llvm-svn: 213416

1 files changed, 14 insertions, 0 deletions

diff --git a/clang/test/Modules/Inputs/macro-hiding/module.modulemap b/clang/test/Modules/Inputs/macro-hiding/module.modulemap
new file mode 100644
index 00000000000..14ca9af86ab
--- /dev/null
+++ b/clang/test/Modules/Inputs/macro-hiding/module.modulemap
@@ -0,0 +1,14 @@
+module a {
+  module a1 { header "a1.h" export * }
+  module a2 { header "a2.h" export * }
+}
+module b {
+  module b1 { header "b1.h" export * }
+  module b2 { header "b2.h" export * }
+}
+module c {
+  module c1 { header "c1.h" export * }
+}
+module d {
+  module d1 { header "d1.h" export * }
+}