[PATCH] Ensure std::getline always 0-terminates string.

[Reimar Döffinger via cfe-commits]

If the sentinel failed (e.g. due to having reached
EOF before) or an exception was caught it failed to
do that.
The C++14 standard says:
"In any case, if n is greater than zero, it then stores
a null character (using charT()) into the next
successive location of the array."
Other implementations like libstdc++ do 0-terminate and
not doing so may lead security issues in applications.
---
 include/istream | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/istream b/include/istream
index 0b8e05d95..5c73df38f 100644
--- a/include/istream
+++ b/include/istream
@@ -1069,16 +1069,18 @@ basic_istream<_CharT, _Traits>::getline(char_type* __s, streamsize __n, char_typ
                 this->rdbuf()->sbumpc();
                 ++__gc_;
             }
-            if (__n > 0)
-                *__s = char_type();
             if (__gc_ == 0)
                __err |= ios_base::failbit;
             this->setstate(__err);
         }
+        if (__n > 0)
+            *__s = char_type();
 #ifndef _LIBCPP_NO_EXCEPTIONS
     }
     catch (...)
     {
+        if (__n > 0)
+            *__s = char_type();
         this->__set_badbit_and_consider_rethrow();
     }
 #endif  // _LIBCPP_NO_EXCEPTIONS
-- 
2.14.2