Fix PR#25973 : 'basic_string::assign(InputIt, InputIt) doesn't provide the strong exception safety guarantee'. This turned out to be a pervasive problem in <string>, which required a fair amount of rework. Add in an optimization for when iterators provide noexcept increment/comparison/assignment/dereference (which covers many of the iterators in libc++). Reviewed as http://reviews.llvm.org/D15862

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@257682 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/strings/basic.string/string.modifiers/string_assign/initializer_list.pass.cpp

@@ -24,7 +24,7 @@ int main()
         s.assign({'a', 'b', 'c'});
         assert(s == "abc");
     }
-#if __cplusplus >= 201103L
+#if TEST_STD_VER >= 11
     {
         typedef std::basic_string<char, std::char_traits<char>, min_allocator<char>> S;
         S s("123");

test/std/strings/basic.string/string.modifiers/string_assign/iterator.pass.cpp

@@ -15,7 +15,7 @@
 #include <string>
 #include <cassert>
 
-#include "../../input_iterator.h"
+#include "test_iterators.h"
 #include "min_allocator.h"
 
 template <class S, class It>
@@ -27,6 +27,20 @@ test(S s, It first, It last, S expected)
     assert(s == expected);
 }
 
+template <class S, class It>
+void
+test_exceptions(S s, It first, It last)
+{
+	S aCopy = s;
+    try {
+   	    s.assign(first, last);
+    	assert(false);
+    	}
+    catch (...) {}
+    assert(s.__invariants());
+    assert(s == aCopy);
+}
+
 int main()
 {
     {
@@ -147,4 +161,17 @@ int main()
          S("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"));
     }
 #endif
+	{ // test iterator operations that throw
+    typedef std::string S;
+    typedef ThrowingIterator<char> TIter;
+    typedef input_iterator<TIter> IIter;
+    const char* s = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
+    test_exceptions(S(), IIter(TIter(s, s+10, 4, TIter::TAIncrement)), IIter());
+    test_exceptions(S(), IIter(TIter(s, s+10, 5, TIter::TADereference)), IIter());
+    test_exceptions(S(), IIter(TIter(s, s+10, 6, TIter::TAComparison)), IIter());
+
+    test_exceptions(S(), TIter(s, s+10, 4, TIter::TAIncrement), TIter());
+    test_exceptions(S(), TIter(s, s+10, 5, TIter::TADereference), TIter());
+    test_exceptions(S(), TIter(s, s+10, 6, TIter::TAComparison), TIter());
+	}
 }

test/std/strings/basic.string/string.modifiers/string_assign/pointer.pass.cpp

@@ -43,7 +43,7 @@ int main()
     test(S("12345678901234567890"), "12345678901234567890",
          S("12345678901234567890"));
     }
-#if __cplusplus >= 201103L
+#if TEST_STD_VER >= 11
     {
     typedef std::basic_string<char, std::char_traits<char>, min_allocator<char>> S;
     test(S(), "", S());

test/std/strings/basic.string/string.modifiers/string_assign/pointer_size.pass.cpp

@@ -48,7 +48,7 @@ int main()
     test(S("12345678901234567890"), "12345678901234567890", 20,
          S("12345678901234567890"));
     }
-#if __cplusplus >= 201103L
+#if TEST_STD_VER >= 11
     {
     typedef std::basic_string<char, std::char_traits<char>, min_allocator<char>> S;
     test(S(), "", 0, S());

test/std/strings/basic.string/string.modifiers/string_assign/rv_string.pass.cpp

@@ -52,7 +52,7 @@ int main()
     test(S("12345678901234567890"), S("12345678901234567890"),
          S("12345678901234567890"));
     }
-#if __cplusplus >= 201103L
+#if TEST_STD_VER >= 11
     {
     typedef std::basic_string<char, std::char_traits<char>, min_allocator<char>> S;
     test(S(), S(), S());

test/std/strings/basic.string/string.modifiers/string_assign/size_char.pass.cpp

@@ -43,7 +43,7 @@ int main()
     test(S("12345678901234567890"), 1, 'a', S(1, 'a'));
     test(S("12345678901234567890"), 10, 'a', S(10, 'a'));
     }
-#if __cplusplus >= 201103L
+#if TEST_STD_VER >= 11
     {
     typedef std::basic_string<char, std::char_traits<char>, min_allocator<char>> S;
     test(S(), 0, 'a', S());

test/std/strings/basic.string/string.modifiers/string_assign/string.pass.cpp

@@ -51,7 +51,7 @@ int main()
     test(S("12345678901234567890"), S("12345678901234567890"),
          S("12345678901234567890"));
     }
-#if __cplusplus >= 201103L
+#if TEST_STD_VER >= 11
     {
     typedef std::basic_string<char, std::char_traits<char>, min_allocator<char>> S;
     test(S(), S(), S());

test/std/strings/basic.string/string.modifiers/string_assign/string_size_size.pass.cpp

@@ -80,7 +80,7 @@ int main()
     test(S("12345678901234567890"), S("12345678901234567890"), 5, 10,
          S("6789012345"));
     }
-#if __cplusplus >= 201103L
+#if TEST_STD_VER >= 11
     {
     typedef std::basic_string<char, std::char_traits<char>, min_allocator<char>> S;
     test(S(), S(), 0, 0, S());