Add pragma to perform module import and use it in -E output.

Many of our supported configurations support modules but do not have any
first-class syntax to perform a module import. This leaves us with a problem:
there is no way to represent the expansion of a #include that imports a module
in the -E output for such languages. (We don't want to just leave it as a
#include because that requires the consumer of the preprocessed source to have
the same file system layout and include paths as the creator.)

This patch adds a new pragma:

  #pragma clang module import MODULE.NAME.HERE

that imports a module, and changes -E and -frewrite-includes to use it when
rewriting a #include that maps to a module import. We don't make any attempt
to use a native language syntax import if one exists, to get more consistent
output. (If in the future, @import and #include have different semantics in
some way, the pragma will track the #include semantics.)


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@301725 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 2 insertions, 0 deletions

diff --git a/include/clang/Basic/DiagnosticLexKinds.td b/include/clang/Basic/DiagnosticLexKinds.td
index 653be75a76..cd284e9430 100644
--- a/include/clang/Basic/DiagnosticLexKinds.td
+++ b/include/clang/Basic/DiagnosticLexKinds.td
@@ -475,6 +475,8 @@ def warn_pragma_pop_macro_no_push : Warning<
 def warn_pragma_message : Warning<"%0">,
    InGroup<PoundPragmaMessage>, DefaultWarnNoWerror;
 def err_pragma_message : Error<"%0">;
+def err_pragma_module_import_expected_module_name : Error<
+  "expected %select{identifier in|'.' or end of directive after}0 module name">;
 def warn_pragma_ignored : Warning<"unknown pragma ignored">,
    InGroup<UnknownPragmas>, DefaultIgnore;
 def ext_stdc_pragma_ignored : ExtWarn<"unknown pragma in STDC namespace">,