[flang] Catch calls to impure intrinsics from PURE subprograms (#160947)

The code in expression semantics that catches a call to an impure
procedure in a PURE context misses calls to impure intrinsics, since
their designators have a SpecificIntrinsic rather than a Symbol. Replace
the current check with a new one that uses the characteristics of the
called procedure, which works for both intrinsic and non-intrinsic
cases.

Testing this change revealed that an explicit INTRINSIC statement wasn't
doing the right thing for extension "dual" intrinsics that can be called
as either a function or as a subroutine; the use of an INTRINSIC
statement would disallow its use as a subroutine. I've fixed that here
as well.

Fixes #157124.

Author: klausler

flang/include/flang/Evaluate/intrinsics.h

@@ -86,6 +86,7 @@ class IntrinsicProcTable {
   bool IsIntrinsic(const std::string &) const;
   bool IsIntrinsicFunction(const std::string &) const;
   bool IsIntrinsicSubroutine(const std::string &) const;
+  bool IsDualIntrinsic(const std::string &) const;
 
   // Inquiry intrinsics are defined in section 16.7, table 16.1
   IntrinsicClass GetIntrinsicClass(const std::string &) const;

flang/lib/Evaluate/intrinsics.cpp

@@ -1674,7 +1674,7 @@ static const IntrinsicInterface intrinsicSubroutine[]{
             {"to", SameIntOrUnsigned, Rank::elemental, Optionality::required,
                 common::Intent::Out},
             {"topos", AnyInt}},
-        {}, Rank::elemental, IntrinsicClass::elementalSubroutine}, // elemental
+        {}, Rank::elemental, IntrinsicClass::elementalSubroutine},
     {"random_init",
         {{"repeatable", AnyLogical, Rank::scalar},
             {"image_distinct", AnyLogical, Rank::scalar}},
@@ -2903,7 +2903,7 @@ bool IntrinsicProcTable::Implementation::IsDualIntrinsic(
   // Collection for some intrinsics with function and subroutine form,
   // in order to pass the semantic check.
   static const std::string dualIntrinsic[]{{"chdir"}, {"etime"}, {"fseek"},
-      {"ftell"}, {"getcwd"}, {"hostnm"}, {"putenv"s}, {"rename"}, {"second"},
+      {"ftell"}, {"getcwd"}, {"hostnm"}, {"putenv"}, {"rename"}, {"second"},
       {"system"}, {"unlink"}};
   return llvm::is_contained(dualIntrinsic, name);
 }
@@ -3766,6 +3766,9 @@ bool IntrinsicProcTable::IsIntrinsicFunction(const std::string &name) const {
 bool IntrinsicProcTable::IsIntrinsicSubroutine(const std::string &name) const {
   return DEREF(impl_.get()).IsIntrinsicSubroutine(name);
 }
+bool IntrinsicProcTable::IsDualIntrinsic(const std::string &name) const {
+  return DEREF(impl_.get()).IsDualIntrinsic(name);
+}
 
 IntrinsicClass IntrinsicProcTable::GetIntrinsicClass(
     const std::string &name) const {

flang/lib/Semantics/expression.cpp

@@ -3644,19 +3644,24 @@ std::optional<characteristics::Procedure> ExpressionAnalyzer::CheckCall(
       Say(callSite,
           "Assumed-length character function must be defined with a length to be called"_err_en_US);
     }
+    if (!chars->IsPure()) {
+      if (const semantics::Scope *pure{semantics::FindPureProcedureContaining(
+              context_.FindScope(callSite))}) {
+        std::string name;
+        if (procSymbol) {
+          name = "'"s + procSymbol->name().ToString() + "'";
+        } else if (const auto *intrinsic{proc.GetSpecificIntrinsic()}) {
+          name = "'"s + intrinsic->name + "'";
+        }
+        Say(callSite,
+            "Procedure %s referenced in pure subprogram '%s' must be pure too"_err_en_US,
+            name, DEREF(pure->symbol()).name());
+      }
+    }
     ok &= semantics::CheckArguments(*chars, arguments, context_,
         context_.FindScope(callSite), treatExternalAsImplicit,
         /*ignoreImplicitVsExplicit=*/false, specificIntrinsic);
   }
-  if (procSymbol && !IsPureProcedure(*procSymbol)) {
-    if (const semantics::Scope *
-        pure{semantics::FindPureProcedureContaining(
-            context_.FindScope(callSite))}) {
-      Say(callSite,
-          "Procedure '%s' referenced in pure subprogram '%s' must be pure too"_err_en_US,
-          procSymbol->name(), DEREF(pure->symbol()).name());
-    }
-  }
   if (ok && !treatExternalAsImplicit && procSymbol &&
       !(chars && chars->HasExplicitInterface())) {
     if (const Symbol *global{FindGlobal(*procSymbol)};

flang/lib/Semantics/resolve-names.cpp

@@ -5726,7 +5726,8 @@ void DeclarationVisitor::DeclareIntrinsic(const parser::Name &name) {
       }
     }
     if (!symbol.test(Symbol::Flag::Function) &&
-        !symbol.test(Symbol::Flag::Subroutine)) {
+        !symbol.test(Symbol::Flag::Subroutine) &&
+        !context().intrinsics().IsDualIntrinsic(name.source.ToString())) {
       if (context().intrinsics().IsIntrinsicFunction(name.source.ToString())) {
         symbol.set(Symbol::Flag::Function);
       } else if (context().intrinsics().IsIntrinsicSubroutine(

flang/test/Semantics/bug157124.f90

@@ -0,0 +1,11 @@
+! RUN: %python %S/test_errors.py %s %flang_fc1
+pure subroutine puresub
+  intrinsic sleep, chdir, get_command
+  character(80) str
+  !ERROR: Procedure 'impureexternal' referenced in pure subprogram 'puresub' must be pure too
+  call impureExternal ! implicit interface
+  !ERROR: Procedure 'sleep' referenced in pure subprogram 'puresub' must be pure too
+  call sleep(1) ! intrinsic subroutine, debatably impure
+  !ERROR: Procedure 'chdir' referenced in pure subprogram 'puresub' must be pure too
+  call chdir('.') ! "dual" function/subroutine, impure
+end