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List:       cfe-commits
Subject:    [PATCH] D11658: [Sema] main can't be declared as global variable
From:       Davide Italiano <dccitaliano () gmail ! com>
Date:       2015-07-30 19:01:22
Message-ID: differential-rev-PHID-DREV-xxfrdy4wzcadmzoaeleu-req () reviews ! llvm ! org
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davide created this revision.
davide added reviewers: aaron.ballman, rsmith.
davide added a subscriber: cfe-commits.

I modeled it in this way: every time we act on a variable declaration, we \
check if it's main and it's global, and in case it's true we emit a \
diagnostic. Actually, to completely fulfill the standard requirements we \
should also consider ill-formed anything that declares the name "main" with \
C linkage, but I'd like to tackle this separately. In particular I'm not \
sure if "name" refers only to variables or also to e.g. function names \
etc.. For reference, this was reported in PR24309. 

http://reviews.llvm.org/D11658

Files:
  include/clang/Basic/DiagnosticSemaKinds.td
  lib/Sema/SemaDecl.cpp
  test/CXX/basic/basic.start/basic.start.main/p3.cpp

Index: test/CXX/basic/basic.start/basic.start.main/p3.cpp
===================================================================
--- test/CXX/basic/basic.start/basic.start.main/p3.cpp
+++ test/CXX/basic/basic.start/basic.start.main/p3.cpp
@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+int main; // expected-error{{main can't be declared as global variable}}
+
+int f () {
+  int main; // OK
+  (void)main;
+}
Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp
+++ lib/Sema/SemaDecl.cpp
@@ -6105,6 +6105,13 @@
     }
   }
 
+  // [basic.start.main]p3
+  // A program that declares a variable main at global scope is \
ill-formed. +  if (getLangOpts().CPlusPlus && Name.getAsString() == "main" \
&& +      NewVD->isFileVarDecl()) {
+      Diag(D.getLocStart(), diag::err_main_global_variable);
+  }
+
   if (D.isRedeclaration() && !Previous.empty()) {
     checkDLLAttributeRedeclaration(
         *this, dyn_cast<NamedDecl>(Previous.getRepresentativeDecl()), \
                NewVD,
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -510,6 +510,7 @@
 def err_main_arg_wrong : Error<"%select{first|second|third|fourth}0 "
     "parameter of 'main' (%select{argument count|argument \
array|environment|"  "platform-specific data}0) must be of type %1">;
+def err_main_global_variable : Error<"main can't be declared as global \
variable">;  def ext_main_used : Extension<
   "ISO C++ does not allow 'main' to be used by a program">, InGroup<Main>;
 


["D11658.31063.patch" (text/x-patch)]

Index: test/CXX/basic/basic.start/basic.start.main/p3.cpp
===================================================================
--- test/CXX/basic/basic.start/basic.start.main/p3.cpp
+++ test/CXX/basic/basic.start/basic.start.main/p3.cpp
@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+int main; // expected-error{{main can't be declared as global variable}}
+
+int f () {
+  int main; // OK
+  (void)main;
+}
Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp
+++ lib/Sema/SemaDecl.cpp
@@ -6105,6 +6105,13 @@
     }
   }
 
+  // [basic.start.main]p3
+  // A program that declares a variable main at global scope is ill-formed.
+  if (getLangOpts().CPlusPlus && Name.getAsString() == "main" &&
+      NewVD->isFileVarDecl()) {
+      Diag(D.getLocStart(), diag::err_main_global_variable);
+  }
+
   if (D.isRedeclaration() && !Previous.empty()) {
     checkDLLAttributeRedeclaration(
         *this, dyn_cast<NamedDecl>(Previous.getRepresentativeDecl()), NewVD,
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -510,6 +510,7 @@
 def err_main_arg_wrong : Error<"%select{first|second|third|fourth}0 "
     "parameter of 'main' (%select{argument count|argument array|environment|"
     "platform-specific data}0) must be of type %1">;
+def err_main_global_variable : Error<"main can't be declared as global variable">;
 def ext_main_used : Extension<
   "ISO C++ does not allow 'main' to be used by a program">, InGroup<Main>;
 


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