[Modules] Make "#pragma weak" undeclared identifiers be tracked

deterministically.

This fixes a latent issue where even Clang's Sema (and diagnostics) were
non-deterministic in the face of this pragma. The fix is super simple --
just use a MapVector so we track the order in which these are parsed (or
imported). Especially considering how rare they are, this seems like the
perfect tradeoff. I've also simplified the client code with judicious
use of auto and range based for loops.

I've added some pretty hilarious code to my stress test which now
survives the binary diff without issue.

llvm-svn: 233261

3 files changed, 33 insertions, 0 deletions

diff --git a/clang/test/Modules/Inputs/stress1/common.h b/clang/test/Modules/Inputs/stress1/common.h
index d2fff1098d9..b158a8e6c1e 100644
--- a/clang/test/Modules/Inputs/stress1/common.h
+++ b/clang/test/Modules/Inputs/stress1/common.h
@@ -35,4 +35,18 @@ struct S01 {};
 struct S02 {};
 }
 
+#pragma weak pragma_weak00
+#pragma weak pragma_weak01
+#pragma weak pragma_weak02
+#pragma weak pragma_weak03
+#pragma weak pragma_weak04
+#pragma weak pragma_weak05
+
+extern "C" int pragma_weak00();
+extern "C" int pragma_weak01();
+extern "C" int pragma_weak02();
+extern "C" int pragma_weak03;
+extern "C" int pragma_weak04;
+extern "C" int pragma_weak05;
+
 #endif
diff --git a/clang/test/Modules/Inputs/stress1/merge00.h b/clang/test/Modules/Inputs/stress1/merge00.h
index c6dccdf5305..b769b0877dd 100644
--- a/clang/test/Modules/Inputs/stress1/merge00.h
+++ b/clang/test/Modules/Inputs/stress1/merge00.h
@@ -1,6 +1,14 @@
 #ifndef STRESS1_MERGE00_H
 #define STRESS1_MERGE00_H
 
+// These don't match the imported declarations because we import them from
+// modules which are built in isolation of the current header's pragma state
+// much like they are built in isolation of the incoming macro state.
+// FIXME: We should expect warnings here but we can't because verify doesn't
+// work for modules.
+//#pragma weak pragma_weak01 // expected-warning {{weak identifier 'pragma_weak01' never declared}}
+//#pragma weak pragma_weak04 // expected-warning {{weak identifier 'pragma_waek04' never declared}}
+
 #include "m00.h"
 #include "m01.h"
 #include "m02.h"
@@ -8,4 +16,10 @@
 
 inline int g() { return N00::S00('a').method00('b') + (int)N00::S00(42) + function00(42); }
 
+#pragma weak pragma_weak02
+#pragma weak pragma_weak05
+
+extern "C" int pragma_weak02();
+int pragma_weak05;
+
 #endif
diff --git a/clang/test/Modules/stress1.cpp b/clang/test/Modules/stress1.cpp
index 55d9533b7ae..e03e538a3ce 100644
--- a/clang/test/Modules/stress1.cpp
+++ b/clang/test/Modules/stress1.cpp
@@ -98,3 +98,8 @@
 #include "merge00.h"
 
 int f() { return N01::S00('a').method00('b') + (int)N00::S00(42) + function00(42) + g(); }
+
+int f2() {
+  return pragma_weak00() + pragma_weak01() + pragma_weak02() +
+         pragma_weak03 + pragma_weak04 + pragma_weak05;
+}