[flang] Enforce F'2023 C1520 correctly (#82842)

When a procedure declaration statement has a binding label, it must
declare no more than one procedure.

Fixes https://github.com/llvm/llvm-project/issues/82528.

2 files changed, 5 insertions, 4 deletions

diff --git a/flang/lib/Semantics/resolve-names.cpp b/flang/lib/Semantics/resolve-names.cpp
index 7fa9b0d..b7b4625 100644
--- a/flang/lib/Semantics/resolve-names.cpp
+++ b/flang/lib/Semantics/resolve-names.cpp
@@ -1118,7 +1118,6 @@ private:
   // Set when walking DATA & array constructor implied DO loop bounds
   // to warn about use of the implied DO intex therein.
   std::optional<SourceName> checkIndexUseInOwnBounds_;
-  bool hasBindCName_{false};
   bool isVectorType_{false};
   UnorderedSymbolSet mustBeScalar_;
 
@@ -5589,7 +5588,10 @@ bool DeclarationVisitor::Pre(const parser::ProcedureDeclarationStmt &x) {
   for (const parser::ProcAttrSpec &procAttr : procAttrSpec) {
     if (auto *bindC{std::get_if<parser::LanguageBindingSpec>(&procAttr.u)}) {
       if (bindC->v.has_value()) {
-        hasBindCName_ = true;
+        if (std::get<std::list<parser::ProcDecl>>(x.t).size() > 1) {
+          Say(context().location().value(),
+              "A procedure declaration statement with a binding name may not declare multiple procedures"_err_en_US);
+        }
         break;
       }
     }
@@ -5598,7 +5600,6 @@ bool DeclarationVisitor::Pre(const parser::ProcedureDeclarationStmt &x) {
 }
 void DeclarationVisitor::Post(const parser::ProcedureDeclarationStmt &) {
   interfaceName_ = nullptr;
-  hasBindCName_ = false;
   EndDecl();
 }
 bool DeclarationVisitor::Pre(const parser::DataComponentDefStmt &x) {
diff --git a/flang/test/Semantics/bind-c04.f90 b/flang/test/Semantics/bind-c04.f90
index a4aaffb..27119e3 100644
--- a/flang/test/Semantics/bind-c04.f90
+++ b/flang/test/Semantics/bind-c04.f90
@@ -19,7 +19,7 @@ subroutine sub(x, y)
     end
   end interface
 
-  !Acceptable (as an extension)
+  !ERROR: A procedure declaration statement with a binding name may not declare multiple procedures
   procedure(proc), bind(c, name="aaa") :: pc1, pc2
 
   !ERROR: A procedure pointer may not have a BIND attribute with a name