Enforce restrictions that 'main' is not allowed to be deleted, or to be used by

the program, in C++. (We allow the latter as an extension, since we've always
permitted it, and GCC does the same, and our supported C++ ABIs don't do
anything special in main.)

llvm-svn: 199782

1 files changed, 6 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 3640c5ad24b..ff54b6b24e4 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -264,13 +264,18 @@ bool Sema::DiagnoseUseOfDecl(NamedDecl *D, SourceLocation Loc,
       SmallVectorImpl<PartialDiagnosticAt> &Suppressed = Pos->second;
       for (unsigned I = 0, N = Suppressed.size(); I != N; ++I)
         Diag(Suppressed[I].first, Suppressed[I].second);
-      
+
       // Clear out the list of suppressed diagnostics, so that we don't emit
       // them again for this specialization. However, we don't obsolete this
       // entry from the table, because we want to avoid ever emitting these
       // diagnostics again.
       Suppressed.clear();
     }
+
+    // C++ [basic.start.main]p3:
+    //   The function 'main' shall not be used within a program.
+    if (cast<FunctionDecl>(D)->isMain())
+      Diag(Loc, diag::ext_main_used);
   }
 
   // See if this is an auto-typed variable whose initializer we are parsing.