[flang] Fix references to destroyed objects

ProgramTree instances are created as the value of a local
variable in the Pre(const parser::ProgramUnit &) member function
in name resolution.  But references to these ProgramTree instances
can persist in SubprogramNameDetails symbol table entries that
might survive that function call's lifetime, and lead to trouble
later when (e.g.) expression semantics needs to deal with a
possible forward reference in a function reference in an expression
being processed later in expression checking.

So put those ProgramTree instances into a longer-lived linked
list within the SemanticsContext.

Might fix some weird crashes reported on big-endian targets
(AIX & Solaris).

Author: klausler

flang/lib/Semantics/program-tree.h renamed to 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-utils.cpp

@@ -31,8 +31,6 @@ using common::NumericOperator;
 using common::RelationalOperator;
 using IntrinsicOperator = parser::DefinedOperator::IntrinsicOperator;
 
-static constexpr const char *operatorPrefix{"operator("};
-
 static GenericKind MapIntrinsicOperator(IntrinsicOperator);
 
 Symbol *Resolve(const parser::Name &name, Symbol *symbol) {
@@ -69,37 +67,6 @@ bool IsIntrinsicOperator(
   return false;
 }
 
-template <typename E>
-std::forward_list<std::string> GetOperatorNames(
-    const SemanticsContext &context, E opr) {
-  std::forward_list<std::string> result;
-  for (const char *name : context.languageFeatures().GetNames(opr)) {
-    result.emplace_front(std::string{operatorPrefix} + name + ')');
-  }
-  return result;
-}
-
-std::forward_list<std::string> GetAllNames(
-    const SemanticsContext &context, const SourceName &name) {
-  std::string str{name.ToString()};
-  if (!name.empty() && name.end()[-1] == ')' &&
-      name.ToString().rfind(std::string{operatorPrefix}, 0) == 0) {
-    for (int i{0}; i != common::LogicalOperator_enumSize; ++i) {
-      auto names{GetOperatorNames(context, LogicalOperator{i})};
-      if (llvm::is_contained(names, str)) {
-        return names;
-      }
-    }
-    for (int i{0}; i != common::RelationalOperator_enumSize; ++i) {
-      auto names{GetOperatorNames(context, RelationalOperator{i})};
-      if (llvm::is_contained(names, str)) {
-        return names;
-      }
-    }
-  }
-  return {str};
-}
-
 bool IsLogicalConstant(
     const SemanticsContext &context, const SourceName &name) {
   std::string str{name.ToString()};

flang/lib/Semantics/resolve-names-utils.h

@@ -51,11 +51,6 @@ parser::MessageFixedText WithSeverity(
 bool IsIntrinsicOperator(const SemanticsContext &, const SourceName &);
 bool IsLogicalConstant(const SemanticsContext &, const SourceName &);
 
-// Some intrinsic operators have more than one name (e.g. `operator(.eq.)` and
-// `operator(==)`). GetAllNames() returns them all, including symbolName.
-std::forward_list<std::string> GetAllNames(
-    const SemanticsContext &, const SourceName &);
-
 template <typename T>
 MaybeIntExpr EvaluateIntExpr(SemanticsContext &context, const T &expr) {
   if (MaybeExpr maybeExpr{

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 {

flang/lib/Semantics/tools.cpp

@@ -1654,6 +1654,37 @@ bool HasDefinedIo(common::DefinedIo which, const DerivedTypeSpec &derived,
   return parentType && HasDefinedIo(which, *parentType, scope);
 }
 
+template <typename E>
+std::forward_list<std::string> GetOperatorNames(
+    const SemanticsContext &context, E opr) {
+  std::forward_list<std::string> result;
+  for (const char *name : context.languageFeatures().GetNames(opr)) {
+    result.emplace_front("operator("s + name + ')');
+  }
+  return result;
+}
+
+std::forward_list<std::string> GetAllNames(
+    const SemanticsContext &context, const SourceName &name) {
+  std::string str{name.ToString()};
+  if (!name.empty() && name.end()[-1] == ')' &&
+      name.ToString().rfind("operator(", 0) == 0) {
+    for (int i{0}; i != common::LogicalOperator_enumSize; ++i) {
+      auto names{GetOperatorNames(context, common::LogicalOperator{i})};
+      if (llvm::is_contained(names, str)) {
+        return names;
+      }
+    }
+    for (int i{0}; i != common::RelationalOperator_enumSize; ++i) {
+      auto names{GetOperatorNames(context, common::RelationalOperator{i})};
+      if (llvm::is_contained(names, str)) {
+        return names;
+      }
+    }
+  }
+  return {str};
+}
+
 void WarnOnDeferredLengthCharacterScalar(SemanticsContext &context,
     const SomeExpr *expr, parser::CharBlock at, const char *what) {
   if (context.languageFeatures().ShouldWarn(