[flang] Check for invalid BIND(C) names

[klausler]

Summary

Require BIND(C) interoperable names to be valid C identifiers.

[jeanPerier]

Looks good

flang/lib/Semantics/check-declarations.cpp

 //===-- lib/Semantics/check-declarations.cpp ------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // Static declaration checking
 
 #include "check-declarations.h"
 #include "pointer-assignment.h"
 #include "flang/Evaluate/check-expression.h"
 #include "flang/Evaluate/fold.h"
 #include "flang/Evaluate/tools.h"
+#include "flang/Parser/characters.h"
 #include "flang/Semantics/scope.h"
 #include "flang/Semantics/semantics.h"
 #include "flang/Semantics/symbol.h"
 #include "flang/Semantics/tools.h"
 #include "flang/Semantics/type.h"
 #include <algorithm>
 #include <map>
 #include <string>

 }
 
 void CheckHelper::CheckBindC(const Symbol &symbol) {
   if (!symbol.attrs().test(Attr::BIND_C)) {
     return;
   }
   CheckConflicting(symbol, Attr::BIND_C, Attr::PARAMETER);
   CheckConflicting(symbol, Attr::BIND_C, Attr::ELEMENTAL);
+  if (const std::string * bindName{symbol.GetBindName()};
+      bindName && !bindName->empty()) {
+    bool ok{bindName->front() == '_' || parser::IsLetter(bindName->front())};
+    for (char ch : *bindName) {
+      ok &= ch == '_' || parser::IsLetter(ch) || parser::IsDecimalDigit(ch);
+    }
+    if (!ok) {
+      messages_.Say(symbol.name(),
+          "Symbol has a BIND(C) name that is not a valid C language identifier"_err_en_US);
+      context_.SetError(symbol);
+    }
+  }
   if (symbol.has<ObjectEntityDetails>() && !symbol.owner().IsModule()) {
     messages_.Say(symbol.name(),
         "A variable with BIND(C) attribute may only appear in the specification part of a module"_err_en_US);
     context_.SetError(symbol);
   }
   if (const auto *proc{symbol.detailsIf<ProcEntityDetails>()}) {
     if (!proc->procInterface() ||
         !proc->procInterface()->attrs().test(Attr::BIND_C)) {

flang/test/Semantics/bind-c10.f90

+! RUN: %python %S/test_errors.py %s %flang_fc1
+!ERROR: Symbol has a BIND(C) name that is not a valid C language identifier
+subroutine bang() bind(C,name='!')
+end
+!ERROR: Symbol has a BIND(C) name that is not a valid C language identifier
+subroutine cr() bind(C,name=achar(13))
+end
+!ERROR: Symbol has a BIND(C) name that is not a valid C language identifier
+subroutine beast() bind(C,name="666")
+end