[flang] Fix bogus error about duplicate binding names (#89786)

Don't call SetBindNameOn() from DeclareUnknownEntity() unless there is
an explicit BIND(C) attribute.

Fixes #89439 and
#89558.

Author: klausler

flang/lib/Semantics/resolve-names.cpp

@@ -1779,7 +1779,6 @@ void AttrsVisitor::SetBindNameOn(Symbol &symbol) {
       !symbol.attrs().test(Attr::BIND_C)) {
     return;
   }
-
   std::optional<std::string> label{
       evaluate::GetScalarConstantValue<evaluate::Ascii>(bindName_)};
   // 18.9.2(2): discard leading and trailing blanks
@@ -1798,16 +1797,18 @@ void AttrsVisitor::SetBindNameOn(Symbol &symbol) {
   } else {
     label = symbol.name().ToString();
   }
-  // Check if a symbol has two Bind names.
+  // Checks whether a symbol has two Bind names.
   std::string oldBindName;
-  if (symbol.GetBindName()) {
-    oldBindName = *symbol.GetBindName();
+  if (const auto *bindName{symbol.GetBindName()}) {
+    oldBindName = *bindName;
   }
   symbol.SetBindName(std::move(*label));
   if (!oldBindName.empty()) {
     if (const std::string * newBindName{symbol.GetBindName()}) {
       if (oldBindName != *newBindName) {
-        Say(symbol.name(), "The entity '%s' has multiple BIND names"_err_en_US);
+        Say(symbol.name(),
+            "The entity '%s' has multiple BIND names ('%s' and '%s')"_err_en_US,
+            symbol.name(), oldBindName, *newBindName);
       }
     }
   }
@@ -4986,7 +4987,9 @@ Symbol &DeclarationVisitor::DeclareUnknownEntity(
     if (symbol.attrs().test(Attr::EXTERNAL)) {
       ConvertToProcEntity(symbol);
     }
-    SetBindNameOn(symbol);
+    if (attrs.test(Attr::BIND_C)) {
+      SetBindNameOn(symbol);
+    }
     return symbol;
   }
 }

flang/test/Semantics/declarations03.f90

@@ -19,7 +19,7 @@ module m
   common /blk4/ w
   bind(c, name="cc") :: t2, /blk4/
 
-  !ERROR: The entity 'blk5' has multiple BIND names
+  !ERROR: The entity 'blk5' has multiple BIND names ('dd' and 'ee')
   common /blk5/ i
   bind(c, name="dd") :: /blk5/
   bind(c, name="ee") :: /blk5/
@@ -29,7 +29,7 @@ module m
   bind(c, name="ff") :: /blk6/
   bind(c, name="ff") :: /blk7/
 
-  !ERROR: The entity 's1' has multiple BIND names
+  !ERROR: The entity 's1' has multiple BIND names ('gg' and 'hh')
   integer :: s1
   bind(c, name="gg") :: s1
   !ERROR: BIND_C attribute was already specified on 's1'
@@ -40,12 +40,12 @@ module m
   bind(c, name="ii") :: s2
   bind(c, name="ii") :: s3
 
-  !ERROR: The entity 's4' has multiple BIND names
+  !ERROR: The entity 's4' has multiple BIND names ('ss1' and 'jj')
   integer, bind(c, name="ss1") :: s4
   !ERROR: BIND_C attribute was already specified on 's4'
   bind(c, name="jj") :: s4
 
-  !ERROR: The entity 's5' has multiple BIND names
+  !ERROR: The entity 's5' has multiple BIND names ('kk' and 'ss2')
   bind(c, name="kk") :: s5
   !ERROR: BIND_C attribute was already specified on 's5'
   integer, bind(c, name="ss2") :: s5
@@ -72,3 +72,8 @@ module b
   !ERROR: Two entities have the same global name 'int'
   integer, bind(c, name="int") :: i
 end module
+
+module c
+  bind(c, name = "AAA") a
+  integer aaa ! ensure no bogus error about multiple binding names
+end module