[libc++] Fix error flags and exceptions propagated from input stream operations

Summary:
Before this patch, we would only ever throw an exception if the badbit
was set on the stream. The Standard is currently very unclear on how
exceptions should be propagated and what error flags should be set by
the input stream operations. This commit changes libc++ to behave under
a different (but valid) interpretation of the Standard. This interpretation
of the Standard matches what other implementations are doing.

I will submit a paper in San Diego to clarify the Standard such that the
interpretation used in this commit (and other implementations) is the only
possible one.

PR21586
PR15949
rdar://problem/15347558

Reviewers: mclow.lists, EricWF

Subscribers: christof, dexonsmith, cfe-commits

Differential Revision: https://reviews.llvm.org/D49863

llvm-svn: 357531

3 files changed, 200 insertions, 2 deletions

diff --git a/libcxx/test/std/strings/basic.string/string.nonmembers/string.io/get_line.pass.cpp b/libcxx/test/std/strings/basic.string/string.nonmembers/string.io/get_line.pass.cpp
index 8e663cb4f60..6069f8e377e 100644
--- a/libcxx/test/std/strings/basic.string/string.nonmembers/string.io/get_line.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.nonmembers/string.io/get_line.pass.cpp
@@ -18,6 +18,7 @@
 #include <cassert>
 
 #include "min_allocator.h"
+#include "test_macros.h"
 
 int main(int, char**)
 {
@@ -77,6 +78,85 @@ int main(int, char**)
         assert(s == L"   ghij");
     }
 #endif
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    {
+        std::basic_stringbuf<char> sb("hello");
+        std::basic_istream<char> is(&sb);
+        is.exceptions(std::ios_base::eofbit);
+
+        std::basic_string<char> s;
+        bool threw = false;
+        try {
+            std::getline(is, s);
+        } catch (std::ios::failure const&) {
+            threw = true;
+        }
+
+        assert(!is.bad());
+        assert(!is.fail());
+        assert( is.eof());
+        assert(threw);
+        assert(s == "hello");
+    }
+    {
+        std::basic_stringbuf<wchar_t> sb(L"hello");
+        std::basic_istream<wchar_t> is(&sb);
+        is.exceptions(std::ios_base::eofbit);
+
+        std::basic_string<wchar_t> s;
+        bool threw = false;
+        try {
+            std::getline(is, s);
+        } catch (std::ios::failure const&) {
+            threw = true;
+        }
+
+        assert(!is.bad());
+        assert(!is.fail());
+        assert( is.eof());
+        assert(threw);
+        assert(s == L"hello");
+    }
+
+    {
+        std::basic_stringbuf<char> sb;
+        std::basic_istream<char> is(&sb);
+        is.exceptions(std::ios_base::failbit);
+
+        std::basic_string<char> s;
+        bool threw = false;
+        try {
+            std::getline(is, s);
+        } catch (std::ios::failure const&) {
+            threw = true;
+        }
+
+        assert(!is.bad());
+        assert( is.fail());
+        assert( is.eof());
+        assert(threw);
+        assert(s == "");
+    }
+    {
+        std::basic_stringbuf<wchar_t> sb;
+        std::basic_istream<wchar_t> is(&sb);
+        is.exceptions(std::ios_base::failbit);
+
+        std::basic_string<wchar_t> s;
+        bool threw = false;
+        try {
+            std::getline(is, s);
+        } catch (std::ios::failure const&) {
+            threw = true;
+        }
+
+        assert(!is.bad());
+        assert( is.fail());
+        assert( is.eof());
+        assert(threw);
+        assert(s == L"");
+    }
+#endif // TEST_HAS_NO_EXCEPTIONS
 
-  return 0;
+    return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.nonmembers/string.io/get_line_delim.pass.cpp b/libcxx/test/std/strings/basic.string/string.nonmembers/string.io/get_line_delim.pass.cpp
index b081b55c920..d7d271bf02c 100644
--- a/libcxx/test/std/strings/basic.string/string.nonmembers/string.io/get_line_delim.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.nonmembers/string.io/get_line_delim.pass.cpp
@@ -18,6 +18,7 @@
 #include <cassert>
 
 #include "min_allocator.h"
+#include "test_macros.h"
 
 int main(int, char**)
 {
@@ -89,6 +90,84 @@ int main(int, char**)
         assert(s == L"   ghij");
     }
 #endif
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    {
+        std::basic_stringbuf<char> sb("hello");
+        std::basic_istream<char> is(&sb);
+        is.exceptions(std::ios::eofbit);
+
+        std::basic_string<char> s;
+        bool threw = false;
+        try {
+            std::getline(is, s, '\n');
+        } catch (std::ios::failure const&) {
+            threw = true;
+        }
+
+        assert(!is.bad());
+        assert(!is.fail());
+        assert( is.eof());
+        assert(threw);
+        assert(s == "hello");
+    }
+    {
+        std::basic_stringbuf<wchar_t> sb(L"hello");
+        std::basic_istream<wchar_t> is(&sb);
+        is.exceptions(std::ios::eofbit);
+
+        std::basic_string<wchar_t> s;
+        bool threw = false;
+        try {
+            std::getline(is, s, L'\n');
+        } catch (std::ios::failure const&) {
+            threw = true;
+        }
+
+        assert(!is.bad());
+        assert(!is.fail());
+        assert( is.eof());
+        assert(threw);
+        assert(s == L"hello");
+    }
+    {
+        std::basic_stringbuf<char> sb;
+        std::basic_istream<char> is(&sb);
+        is.exceptions(std::ios::failbit);
+
+        std::basic_string<char> s;
+        bool threw = false;
+        try {
+            std::getline(is, s, '\n');
+        } catch (std::ios::failure const&) {
+            threw = true;
+        }
+
+        assert(!is.bad());
+        assert( is.fail());
+        assert( is.eof());
+        assert(threw);
+        assert(s == "");
+    }
+    {
+        std::basic_stringbuf<wchar_t> sb;
+        std::basic_istream<wchar_t> is(&sb);
+        is.exceptions(std::ios::failbit);
+
+        std::basic_string<wchar_t> s;
+        bool threw = false;
+        try {
+            std::getline(is, s, L'\n');
+        } catch (std::ios::failure const&) {
+            threw = true;
+        }
+
+        assert(!is.bad());
+        assert( is.fail());
+        assert( is.eof());
+        assert(threw);
+        assert(s == L"");
+    }
+#endif // TEST_HAS_NO_EXCEPTIONS
 
-  return 0;
+    return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.nonmembers/string.io/stream_extract.pass.cpp b/libcxx/test/std/strings/basic.string/string.nonmembers/string.io/stream_extract.pass.cpp
index 389701d1d51..92061e2c476 100644
--- a/libcxx/test/std/strings/basic.string/string.nonmembers/string.io/stream_extract.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.nonmembers/string.io/stream_extract.pass.cpp
@@ -18,6 +18,7 @@
 #include <cassert>
 
 #include "min_allocator.h"
+#include "test_macros.h"
 
 int main(int, char**)
 {
@@ -65,6 +66,44 @@ int main(int, char**)
         in >> s;
         assert(in.fail());
     }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    {
+        std::stringbuf sb;
+        std::istream is(&sb);
+        is.exceptions(std::ios::failbit);
+
+        bool threw = false;
+        try {
+            std::string s;
+            is >> s;
+        } catch (std::ios::failure const&) {
+            threw = true;
+        }
+
+        assert(!is.bad());
+        assert(is.fail());
+        assert(is.eof());
+        assert(threw);
+    }
+    {
+        std::stringbuf sb;
+        std::istream is(&sb);
+        is.exceptions(std::ios::eofbit);
+
+        bool threw = false;
+        try {
+            std::string s;
+            is >> s;
+        } catch (std::ios::failure const&) {
+            threw = true;
+        }
+
+        assert(!is.bad());
+        assert(is.fail());
+        assert(is.eof());
+        assert(threw);
+    }
+#endif // TEST_HAS_NO_EXCEPTIONS
 #if TEST_STD_VER >= 11
     {
         typedef std::basic_string<char, std::char_traits<char>, min_allocator<char>> S;