[gcc(refs/users/giulianob/heads/autopar_rebase2)] Add a __nonnnull__ attribute to std::string's _CharT* constructor

[Giuliano Belinassi]

https://gcc.gnu.org/g:315b401c176329abce8aeee0462275323fbc56f0

commit 315b401c176329abce8aeee0462275323fbc56f0
Author: Ville Voutilainen <ville.voutilainen@gmail.com>
Date:   Mon Jun 29 00:47:05 2020 +0300

    Add a __nonnnull__ attribute to std::string's _CharT* constructor
    
            Add a __nonnnull__ attribute to std::string's _CharT* constructor
            * include/bits/basic_string.h (string(_CharT*, const _Alloc&)):
            Add a __nonnull__ attribute.
            * testsuite/21_strings/basic_string/cons/char/nonnull.cc: New.
            * testsuite/21_strings/basic_string/cons/wchar_t/nonnull.cc: Likewise.

Diff:
---
 libstdc++-v3/include/bits/basic_string.h           |  1 +
 .../21_strings/basic_string/cons/char/nonnull.cc   | 29 ++++++++++++++++++++++
 .../basic_string/cons/wchar_t/nonnull.cc           | 29 ++++++++++++++++++++++
 3 files changed, 59 insertions(+)

diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h
index bc0c256b65e..d5e5eb06e1b 100644
--- a/libstdc++-v3/include/bits/basic_string.h
+++ b/libstdc++-v3/include/bits/basic_string.h
@@ -522,6 +522,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
       // 3076. basic_string CTAD ambiguity
       template<typename = _RequireAllocator<_Alloc>>
 #endif
+      __attribute__((__nonnull__))
       basic_string(const _CharT* __s, const _Alloc& __a = _Alloc())
       : _M_dataplus(_M_local_data(), __a)
       { _M_construct(__s, __s ? __s + traits_type::length(__s) : __s+npos); }
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/cons/char/nonnull.cc b/libstdc++-v3/testsuite/21_strings/basic_string/cons/char/nonnull.cc
new file mode 100644
index 00000000000..1c09a1d2207
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/cons/char/nonnull.cc
@@ -0,0 +1,29 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-additional-options "-Wnonnull" }
+// { dg-do compile { target c++11 } }
+
+#include <string>
+
+void
+test01()
+{
+  std::string s((const char*)nullptr); // { dg-warning "null arg" }
+  std::string t((char*)nullptr);       // { dg-warning "null arg" }
+  std::string u(nullptr);	       // { dg-warning "null arg" }
+}
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/cons/wchar_t/nonnull.cc b/libstdc++-v3/testsuite/21_strings/basic_string/cons/wchar_t/nonnull.cc
new file mode 100644
index 00000000000..456efed6c8c
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/cons/wchar_t/nonnull.cc
@@ -0,0 +1,29 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-additional-options "-Wnonnull" }
+// { dg-do compile { target c++11 } }
+
+#include <string>
+
+void
+test01()
+{
+  std::wstring s((const wchar_t*)nullptr); // { dg-warning "null arg" }
+  std::wstring t((wchar_t*)nullptr);	   // { dg-warning "null arg" }
+  std::wstring u(nullptr);		   // { dg-warning "null arg" }
+}