[flang] Fixed a crash with undeclared variable in implicit-do loop

[eugeneepshteyn]

Fixed a crash in the following example:

subroutine sub()
  implicit none
  print *, (i, i = 1, 2)  ! Problem: using undefined var in implied-do loop
end subroutine sub

The error message was already generated, but the compiler crashed before it could display it.

[llvmbot]

@llvm/pr-subscribers-flang-semantics

Author: Eugene Epshteyn (eugeneepshteyn)

Changes

Fixed a crash in the following example:

subroutine sub()
  implicit none
  print *, (i, i = 1, 2)  ! Problem: using undefined var in implied-do loop
end subroutine sub

The error message was already generated, but the compiler crashed before it could display it.

---

Full diff: https://github.com/llvm/llvm-project/pull/149513.diff

3 Files Affected:

• (modified) flang/lib/Semantics/check-do-forall.cpp (+3-1)
• (modified) flang/lib/Semantics/resolve-names.cpp (+1-1)
• (modified) flang/test/Semantics/resolve40.f90 (+7)

diff --git a/flang/lib/Semantics/check-do-forall.cpp b/flang/lib/Semantics/check-do-forall.cpp
index cc1d4bf58745a..e258df86a4b1c 100644
--- a/flang/lib/Semantics/check-do-forall.cpp
+++ b/flang/lib/Semantics/check-do-forall.cpp
@@ -1180,7 +1180,9 @@ void DoForallChecker::Leave(const parser::IoControlSpec &ioControlSpec) {
 void DoForallChecker::Leave(const parser::OutputImpliedDo &outputImpliedDo) {
   const auto &control{std::get<parser::IoImpliedDoControl>(outputImpliedDo.t)};
   const parser::Name &name{control.name.thing.thing};
-  context_.CheckIndexVarRedefine(name.source, *name.symbol);
+  if (name.symbol) {
+    context_.CheckIndexVarRedefine(name.source, *name.symbol);
+  }
 }
 
 void DoForallChecker::Leave(const parser::StatVariable &statVariable) {
diff --git a/flang/lib/Semantics/resolve-names.cpp b/flang/lib/Semantics/resolve-names.cpp
index b3268605e7c0c..deafdbd269c78 100644
--- a/flang/lib/Semantics/resolve-names.cpp
+++ b/flang/lib/Semantics/resolve-names.cpp
@@ -8700,7 +8700,7 @@ const parser::Name *DeclarationVisitor::ResolveName(const parser::Name &name) {
     return &name;
   }
   if (isImplicitNoneType() && !deferImplicitTyping_) {
-    Say(name, "No explicit type declared for '%s'"_err_en_US);
+    Say(name, "No explicit type declared for '%s'"_err_en_US, name.source);
     return nullptr;
   }
   // Create the symbol, then ensure that it is accessible
diff --git a/flang/test/Semantics/resolve40.f90 b/flang/test/Semantics/resolve40.f90
index a91507aa62282..81bb5f989ec48 100644
--- a/flang/test/Semantics/resolve40.f90
+++ b/flang/test/Semantics/resolve40.f90
@@ -96,3 +96,10 @@ subroutine s12(x)
   !BECAUSE: 'x' is an INTENT(IN) dummy argument
   read(*,nml=nl)
 end
+
+subroutine s13()
+  implicit none
+  !ERROR: No explicit type declared for 'i'
+  !ERROR: No explicit type declared for 'i'
+  print *, (i, i = 1, 2)
+end