[flang] Fix references to destroyed objects

flang/lib/Semantics/program-tree.h → flang/include/flang/Semantics/program-tree.h

@@ -9,8 +9,8 @@
 #ifndef FORTRAN_SEMANTICS_PROGRAM_TREE_H_
 #define FORTRAN_SEMANTICS_PROGRAM_TREE_H_
 
+#include "symbol.h"
 #include "flang/Parser/parse-tree.h"
-#include "flang/Semantics/symbol.h"
 #include <list>
 #include <variant>
 
@@ -35,7 +35,7 @@ class ProgramTree {
       std::list<common::Reference<const parser::GenericSpec>>;
 
   // Build the ProgramTree rooted at one of these program units.
-  static ProgramTree Build(const parser::ProgramUnit &, SemanticsContext &);
+  static ProgramTree &Build(const parser::ProgramUnit &, SemanticsContext &);
   static std::optional<ProgramTree> Build(
       const parser::MainProgram &, SemanticsContext &);
   static std::optional<ProgramTree> Build(

flang/include/flang/Semantics/semantics.h

@@ -9,6 +9,8 @@
 #ifndef FORTRAN_SEMANTICS_SEMANTICS_H_
 #define FORTRAN_SEMANTICS_SEMANTICS_H_
 
+#include "module-dependences.h"
+#include "program-tree.h"
 #include "scope.h"
 #include "symbol.h"
 #include "flang/Common/Fortran-features.h"
@@ -17,7 +19,6 @@
 #include "flang/Evaluate/intrinsics.h"
 #include "flang/Evaluate/target.h"
 #include "flang/Parser/message.h"
-#include "flang/Semantics/module-dependences.h"
 #include <iosfwd>
 #include <set>
 #include <string>
@@ -280,6 +281,9 @@ class SemanticsContext {
 
   void DumpSymbols(llvm::raw_ostream &);
 
+  // Top-level ProgramTrees are owned by the SemanticsContext for persistence.
+  ProgramTree &SaveProgramTree(ProgramTree &&);
+
 private:
   struct ScopeIndexComparator {
     bool operator()(parser::CharBlock, parser::CharBlock) const;
@@ -331,6 +335,7 @@ class SemanticsContext {
   ModuleDependences moduleDependences_;
   std::map<const Symbol *, SourceName> moduleFileOutputRenamings_;
   UnorderedSymbolSet isDefined_;
+  std::list<ProgramTree> programTrees_;
 };
 
 class Semantics {

flang/lib/Semantics/program-tree.cpp

@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "program-tree.h"
+#include "flang/Semantics/program-tree.h"
 #include "flang/Common/idioms.h"
 #include "flang/Parser/char-block.h"
 #include "flang/Semantics/scope.h"
@@ -130,13 +130,13 @@ static ProgramTree BuildModuleTree(
   return node;
 }
 
-ProgramTree ProgramTree::Build(
+ProgramTree &ProgramTree::Build(
     const parser::ProgramUnit &x, SemanticsContext &context) {
   return common::visit(
-      [&](const auto &y) {
+      [&](const auto &y) -> ProgramTree & {
         auto node{Build(y.value(), context)};
         CHECK(node.has_value());
-        return std::move(*node);
+        return context.SaveProgramTree(std::move(*node));
       },
       x.u);
 }

flang/lib/Semantics/resolve-names.cpp

@@ -10,7 +10,6 @@
 #include "definable.h"
 #include "mod-file.h"
 #include "pointer-assignment.h"
-#include "program-tree.h"
 #include "resolve-directives.h"
 #include "resolve-names-utils.h"
 #include "rewrite-parse-tree.h"
@@ -32,6 +31,7 @@
 #include "flang/Parser/tools.h"
 #include "flang/Semantics/attr.h"
 #include "flang/Semantics/expression.h"
+#include "flang/Semantics/program-tree.h"
 #include "flang/Semantics/scope.h"
 #include "flang/Semantics/semantics.h"
 #include "flang/Semantics/symbol.h"
@@ -2490,6 +2490,7 @@ Symbol &ScopeHandler::CopySymbol(const SourceName &name, const Symbol &symbol) {
 }
 
 // Look for name only in scope, not in enclosing scopes.
+
 Symbol *ScopeHandler::FindInScope(
     const Scope &scope, const parser::Name &name) {
   return Resolve(name, FindInScope(scope, name.source));
@@ -9120,7 +9121,7 @@ bool ResolveNamesVisitor::Pre(const parser::ProgramUnit &x) {
     ResolveAccParts(context(), x, &topScope_);
     return false;
   }
-  auto root{ProgramTree::Build(x, context())};
+  ProgramTree &root{ProgramTree::Build(x, context())};
   SetScope(topScope_);
   ResolveSpecificationParts(root);
   FinishSpecificationParts(root);

flang/lib/Semantics/semantics.cpp

@@ -663,6 +663,10 @@ void SemanticsContext::DumpSymbols(llvm::raw_ostream &os) {
   DoDumpSymbols(os, globalScope());
 }
 
+ProgramTree &SemanticsContext::SaveProgramTree(ProgramTree &&tree) {
+  return programTrees_.emplace_back(std::move(tree));
+}
+
 void Semantics::DumpSymbols(llvm::raw_ostream &os) { context_.DumpSymbols(os); }
 
 void Semantics::DumpSymbolsSources(llvm::raw_ostream &os) const {