[PATCH] Avoid signed overflow in num_get::_M_extract_int (PR libstdc++/67214)

[Xi Ruoyao]

This UB has been hiding so long...

2017-03-11  Xi Ruoyao  <r...@stu.xidian.edu.cn>

        PR libstdc++/67214
        * include/bits/locale_facets.tcc (_M_extract_int):
          Add explicit conversion to avoid signed overflow.
---
 libstdc++-v3/include/bits/locale_facets.tcc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/bits/locale_facets.tcc 
b/libstdc++-v3/include/bits/locale_facets.tcc
index 351190c..5f85d15 100644
--- a/libstdc++-v3/include/bits/locale_facets.tcc
+++ b/libstdc++-v3/include/bits/locale_facets.tcc
@@ -470,7 +470,8 @@ _GLIBCXX_BEGIN_NAMESPACE_LDBL
        bool __testoverflow = false;
        const __unsigned_type __max =
          (__negative && __gnu_cxx::__numeric_traits<_ValueT>::__is_signed)
-         ? -__gnu_cxx::__numeric_traits<_ValueT>::__min
+         ? -static_cast<__unsigned_type>(__gnu_cxx::
+                        __numeric_traits<_ValueT>::__min)
          : __gnu_cxx::__numeric_traits<_ValueT>::__max;
        const __unsigned_type __smax = __max / __base;
        __unsigned_type __result = 0;
-- 
2.7.1

-- 
Xi Ruoyao <r...@stu.xidian.edu.cn>
School of Aerospace Science and Technology, Xidian University