Decorate string_view members with nonnull attribute

The C++ committee has confirmed that passing a null pointer to the
unary basic_string_view constructor is undefined. This removes the check
from our implementation, and adds the nonnull attribute to warn when the
compiler can detect undefined input.

	* include/std/string_view (basic_string_view(const CharT*)): Remove
	check for null pointer and add nonnull attribute.
	(compare(const CharT*), compare(size_type, size_type, const CharT*))
	(find(const CharT*, size_type), rfind(const CharT*, size_type))
	(find_first_of(const CharT*, size_type))
	(find_last_of(const CharT*, size_type))
	(find_first_not_of(const CharT*, size_type))
	(find_last_not_of(const CharT*, size_type)): Add nonnull attribute.
	* testsuite/21_strings/basic_string_view/cons/char/nonnull.cc: New.
	* testsuite/21_strings/basic_string_view/operations/compare/char/
	nonnull.cc: New.
	* testsuite/21_strings/basic_string_view/operations/find/char/
	nonnull.cc: New.
	* testsuite/21_strings/basic_string_view/operations/rfind/char/
	nonnull.cc: New.

From-SVN: r261638

libstdc++-v3/ChangeLog

 2018-06-15  Jonathan Wakely  <jwakely@redhat.com>
 
+	* include/std/string_view (basic_string_view(const CharT*)): Remove
+	check for null pointer and add nonnull attribute.
+	(compare(const CharT*), compare(size_type, size_type, const CharT*))
+	(find(const CharT*, size_type), rfind(const CharT*, size_type))
+	(find_first_of(const CharT*, size_type))
+	(find_last_of(const CharT*, size_type))
+	(find_first_not_of(const CharT*, size_type))
+	(find_last_not_of(const CharT*, size_type)): Add nonnull attribute.
+	* testsuite/21_strings/basic_string_view/cons/char/nonnull.cc: New.
+	* testsuite/21_strings/basic_string_view/operations/compare/char/
+	nonnull.cc: New.
+	* testsuite/21_strings/basic_string_view/operations/find/char/
+	nonnull.cc: New.
+	* testsuite/21_strings/basic_string_view/operations/rfind/char/
+	nonnull.cc: New.
+
 	PR libstdc++/86168
 	* include/bits/random.h (random_device(const string&)): Remove
 	default argument.

libstdc++-v3/include/std/string_view

@@ -96,8 +96,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
       constexpr basic_string_view(const basic_string_view&) noexcept = default;
 
-      constexpr basic_string_view(const _CharT* __str) noexcept
-      : _M_len{__str == nullptr ? 0 : traits_type::length(__str)},
+      __attribute__((__nonnull__)) constexpr
+      basic_string_view(const _CharT* __str) noexcept
+      : _M_len{traits_type::length(__str)},
 	_M_str{__str}
       { }
 
@@ -270,11 +271,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	return this->substr(__pos1, __n1).compare(__str.substr(__pos2, __n2));
       }
 
-      constexpr int
+      __attribute__((__nonnull__)) constexpr int
       compare(const _CharT* __str) const noexcept
       { return this->compare(basic_string_view{__str}); }
 
-      constexpr int
+      __attribute__((__nonnull__)) constexpr int
       compare(size_type __pos1, size_type __n1, const _CharT* __str) const
       { return this->substr(__pos1, __n1).compare(basic_string_view{__str}); }
 
@@ -296,7 +297,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       constexpr size_type
       find(const _CharT* __str, size_type __pos, size_type __n) const noexcept;
 
-      constexpr size_type
+      __attribute__((__nonnull__)) constexpr size_type
       find(const _CharT* __str, size_type __pos = 0) const noexcept
       { return this->find(__str, __pos, traits_type::length(__str)); }
 
@@ -310,7 +311,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       constexpr size_type
       rfind(const _CharT* __str, size_type __pos, size_type __n) const noexcept;
 
-      constexpr size_type
+      __attribute__((__nonnull__)) constexpr size_type
       rfind(const _CharT* __str, size_type __pos = npos) const noexcept
       { return this->rfind(__str, __pos, traits_type::length(__str)); }
 
@@ -323,9 +324,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       { return this->find(__c, __pos); }
 
       constexpr size_type
-      find_first_of(const _CharT* __str, size_type __pos, size_type __n) const noexcept;
+      find_first_of(const _CharT* __str, size_type __pos,
+		    size_type __n) const noexcept;
 
-      constexpr size_type
+      __attribute__((__nonnull__)) constexpr size_type
       find_first_of(const _CharT* __str, size_type __pos = 0) const noexcept
       { return this->find_first_of(__str, __pos, traits_type::length(__str)); }
 
@@ -342,7 +344,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       find_last_of(const _CharT* __str, size_type __pos,
 		   size_type __n) const noexcept;
 
-      constexpr size_type
+      __attribute__((__nonnull__)) constexpr size_type
       find_last_of(const _CharT* __str, size_type __pos = npos) const noexcept
       { return this->find_last_of(__str, __pos, traits_type::length(__str)); }
 
@@ -358,7 +360,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       find_first_not_of(const _CharT* __str,
 			size_type __pos, size_type __n) const noexcept;
 
-      constexpr size_type
+      __attribute__((__nonnull__)) constexpr size_type
       find_first_not_of(const _CharT* __str, size_type __pos = 0) const noexcept
       {
 	return this->find_first_not_of(__str, __pos,
@@ -377,7 +379,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       find_last_not_of(const _CharT* __str,
 		       size_type __pos, size_type __n) const noexcept;
 
-      constexpr size_type
+      __attribute__((__nonnull__)) constexpr size_type
       find_last_not_of(const _CharT* __str,
 		       size_type __pos = npos) const noexcept
       {

libstdc++-v3/testsuite/21_strings/basic_string_view/cons/char/nonnull.cc

+// Copyright (C) 2018 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-options "-std=gnu++17 -Wnonnull" }
+// { dg-do compile { target c++17 } }
+
+#include <string_view>
+
+void
+test01()
+{
+  std::string_view s((const char*)nullptr); // { dg-warning "null arg" }
+  std::string_view t((char*)nullptr);	    // { dg-warning "null arg" }
+  std::string_view u(nullptr);		    // { dg-warning "null arg" }
+}

libstdc++-v3/testsuite/21_strings/basic_string_view/cons/wchar_t/nonnull.cc

+// Copyright (C) 2018 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-options "-std=gnu++17 -Wnonnull" }
+// { dg-do compile { target c++17 } }
+
+#include <string_view>
+
+void
+test01()
+{
+  std::wstring_view s((const wchar_t*)nullptr);	// { dg-warning "null arg" }
+  std::wstring_view t((wchar_t*)nullptr);	// { dg-warning "null arg" }
+  std::wstring_view u(nullptr);			// { dg-warning "null arg" }
+}

libstdc++-v3/testsuite/21_strings/basic_string_view/operations/compare/char/nonnull.cc

+// Copyright (C) 2018 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-options "-std=gnu++17 -Wnonnull" }
+// { dg-do compile { target c++17 } }
+
+#include <string_view>
+
+int
+test01()
+{
+  std::string_view s = "abcd";
+  return s.compare((const char*)nullptr);	// { dg-warning "null arg" }
+  return s.compare(0, 2, (const char*)nullptr);	// { dg-warning "null arg" }
+}

libstdc++-v3/testsuite/21_strings/basic_string_view/operations/find/char/nonnull.cc

+// Copyright (C) 2018 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-options "-std=gnu++17 -Wnonnull" }
+// { dg-do compile { target c++17 } }
+
+#include <string_view>
+
+int
+test01()
+{
+  std::string_view s = "abcd";
+  return s.find((const char*)nullptr);		// { dg-warning "null arg" }
+  return s.find((const char*)nullptr, 1);	// { dg-warning "null arg" }
+  return s.find_first_of((const char*)nullptr);	// { dg-warning "null arg" }
+  return s.find_first_of((const char*)nullptr, 1); // { dg-warning "null arg" }
+  return s.find_first_not_of((const char*)nullptr); // { dg-warning "null arg" }
+  return s.find_first_not_of((const char*)nullptr, 1); // { dg-warning "null arg" }
+}

libstdc++-v3/testsuite/21_strings/basic_string_view/operations/rfind/char/nonnull.cc

+// Copyright (C) 2018 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-options "-std=gnu++17 -Wnonnull" }
+// { dg-do compile { target c++17 } }
+
+#include <string_view>
+
+int
+test01()
+{
+  std::string_view s = "abcd";
+  return s.rfind((const char*)nullptr);		// { dg-warning "null arg" }
+  return s.rfind((const char*)nullptr, 1);	// { dg-warning "null arg" }
+}