From 2b9e3e396a6f0b1ebd247cb204f20a319f6ae7f4 Mon Sep 17 00:00:00 2001
From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Fri, 18 Oct 2013 06:05:18 +0000
Subject: Basic ODR checking for C++ modules:

If we have multiple definitions of the same entity from different modules, we
nominate the first definition which we see as being the canonical definition.
If we load a declaration from a different definition and we can't find a
corresponding declaration in the canonical definition, issue a diagnostic.

This is insufficient to prevent things from going horribly wrong in all cases
-- we might be in the middle of emitting IR for a function when we trigger some
deserialization and discover that it refers to an incoherent piece of the AST,
by which point it's probably too late to bail out -- but we'll at least produce
a diagnostic.

llvm-svn: 192950
---
 clang/lib/Serialization/ASTReader.cpp | 61 ++++++++++++++++++++++++++++++++++-
 1 file changed, 60 insertions(+), 1 deletion(-)

(limited to 'clang/lib/Serialization/ASTReader.cpp')

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 9bb9a7a8632..bafe74b174a 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -7337,7 +7337,8 @@ void ASTReader::ReadComments() {
 
 void ASTReader::finishPendingActions() {
   while (!PendingIdentifierInfos.empty() || !PendingDeclChains.empty() ||
-         !PendingMacroIDs.empty() || !PendingDeclContextInfos.empty()) {
+         !PendingMacroIDs.empty() || !PendingDeclContextInfos.empty() ||
+         !PendingOdrMergeChecks.empty()) {
     // If any identifiers with corresponding top-level declarations have
     // been loaded, load those declarations now.
     typedef llvm::DenseMap<IdentifierInfo *, SmallVector<Decl *, 2> >
@@ -7400,6 +7401,64 @@ void ASTReader::finishPendingActions() {
       DeclContext *LexicalDC = cast<DeclContext>(GetDecl(Info.LexicalDC));
       Info.D->setDeclContextsImpl(SemaDC, LexicalDC, getContext());
     }
+
+    // For each declaration from a merged context, check that the canonical
+    // definition of that context also contains a declaration of the same
+    // entity.
+    while (!PendingOdrMergeChecks.empty()) {
+      NamedDecl *D = PendingOdrMergeChecks.pop_back_val();
+
+      // FIXME: Skip over implicit declarations for now. This matters for things
+      // like implicitly-declared special member functions. This isn't entirely
+      // correct; we can end up with multiple unmerged declarations of the same
+      // implicit entity.
+      if (D->isImplicit())
+        continue;
+
+      DeclContext *CanonDef = D->getDeclContext();
+      DeclContext::lookup_result R = CanonDef->lookup(D->getDeclName());
+
+      bool Found = false;
+      const Decl *DCanon = D->getCanonicalDecl();
+
+      llvm::SmallVector<const NamedDecl*, 4> Candidates;
+      for (DeclContext::lookup_iterator I = R.begin(), E = R.end();
+           !Found && I != E; ++I) {
+        for (Decl::redecl_iterator RI = (*I)->redecls_begin(),
+                                   RE = (*I)->redecls_end();
+             RI != RE; ++RI) {
+          if ((*RI)->getLexicalDeclContext() == CanonDef) {
+            // This declaration is present in the canonical definition. If it's
+            // in the same redecl chain, it's the one we're looking for.
+            if ((*RI)->getCanonicalDecl() == DCanon)
+              Found = true;
+            else
+              Candidates.push_back(cast<NamedDecl>(*RI));
+            break;
+          }
+        }
+      }
+
+      if (!Found) {
+        D->setInvalidDecl();
+
+        Module *CanonDefModule = cast<Decl>(CanonDef)->getOwningModule();
+        Diag(D->getLocation(), diag::err_module_odr_violation_missing_decl)
+          << D << D->getOwningModule()->getFullModuleName()
+          << CanonDef << !CanonDefModule
+          << (CanonDefModule ? CanonDefModule->getFullModuleName() : "");
+
+        if (Candidates.empty())
+          Diag(cast<Decl>(CanonDef)->getLocation(),
+               diag::note_module_odr_violation_no_possible_decls) << D;
+        else {
+          for (unsigned I = 0, N = Candidates.size(); I != N; ++I)
+            Diag(Candidates[I]->getLocation(),
+                 diag::note_module_odr_violation_possible_decl)
+              << Candidates[I];
+        }
+      }
+    }
   }
   
   // If we deserialized any C++ or Objective-C class definitions, any
-- 
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