Add USE association details to COMMON blocks

Author: eugeneepshteyn

flang/include/flang/Semantics/scope.h

@@ -189,6 +189,7 @@ class Scope {
   mapType &commonBlocks() { return commonBlocks_; }
   const mapType &commonBlocks() const { return commonBlocks_; }
   Symbol &MakeCommonBlock(SourceName, SourceName location);
+  bool AddCommonBlock(const SourceName &name, Symbol &cbSymbol);
 
   /// Find COMMON block in the current scope
   Symbol *FindCB(const SourceName &name) const {

flang/lib/Semantics/check-declarations.cpp

@@ -2782,7 +2782,10 @@ void CheckHelper::Check(const Scope &scope) {
       Check(*scope.symbol());
     }
     for (const auto &pair : scope.commonBlocks()) {
-      CheckCommonBlock(*pair.second);
+      if (pair.second->has<CommonBlockDetails>()) {
+        // Only process actual COMMON block objects, not their uses
+        CheckCommonBlock(*pair.second);
+      }
     }
     int mainProgCnt{0};
     for (const Scope &child : scope.children()) {

flang/lib/Semantics/compute-offsets.cpp

@@ -207,7 +207,10 @@ void ComputeOffsetsHelper::Compute(Scope &scope) {
   // where COMMON blocks are illegal (C1107 and C1108).
   if (scope.kind() != Scope::Kind::BlockConstruct) {
     for (auto &pair : scope.commonBlocks()) {
-      DoCommonBlock(*pair.second);
+      // Only process actual COMMON block objects, not their uses
+      if (pair.second->has<CommonBlockDetails>()) {
+        DoCommonBlock(*pair.second);
+      }
     }
   }
   for (auto &[symbol, dep] : dependents_) {

flang/lib/Semantics/resolve-names.cpp

@@ -3627,6 +3627,17 @@ void ModuleVisitor::Post(const parser::UseStmt &x) {
       }
     }
   }
+  // Go through the list of COMMON block symbols in the module scope and add
+  // their USE association to the current scope's COMMON blocks.
+  for (const auto &[name, symbol] : useModuleScope_->commonBlocks()) {
+    if (auto *localCB{currScope().FindCommonBlockInScopes(name)}; !localCB) {
+      // Make a symbol, but don't add it to the Scope, since it needs to
+      // be added to the COMMON blocks
+      localCB = &currScope().MakeSymbol(
+          name, symbol->attrs(), UseDetails{name, symbol->GetUltimate()});
+      currScope().AddCommonBlock(name, *localCB);
+    }
+  }
   useModuleScope_ = nullptr;
 }
 
@@ -7284,6 +7295,10 @@ void DeclarationVisitor::CheckCommonBlocks() {
   // check for empty common blocks
   for (const auto &pair : currScope().commonBlocks()) {
     const auto &symbol{*pair.second};
+    if (!pair.second->has<CommonBlockDetails>()) {
+      // Skip USE associated COMMON blocks
+      continue;
+    }
     if (symbol.get<CommonBlockDetails>().objects().empty() &&
         symbol.attrs().test(Attr::BIND_C)) {
       Say(symbol.name(),

flang/lib/Semantics/scope.cpp

@@ -144,9 +144,8 @@ void Scope::add_crayPointer(const SourceName &name, Symbol &pointer) {
 }
 
 Symbol &Scope::MakeCommonBlock(SourceName name, SourceName location) {
-  const auto it{commonBlocks_.find(name)};
-  if (it != commonBlocks_.end()) {
-    return *it->second;
+  if (auto *cb{FindCB(name)}) {
+    return *cb;
   } else {
     Symbol &symbol{MakeSymbol(
         name, Attrs{}, CommonBlockDetails{name.empty() ? location : name})};
@@ -191,6 +190,11 @@ Scope *Scope::FindSubmodule(const SourceName &name) const {
     return &*it->second;
   }
 }
+
+bool Scope::AddCommonBlock(const SourceName &name, Symbol &cbSymbol) {
+  return commonBlocks_.emplace(name, cbSymbol).second;
+}
+
 bool Scope::AddSubmodule(const SourceName &name, Scope &submodule) {
   return submodules_.emplace(name, submodule).second;
 }