diff options
Diffstat (limited to 'basebmp')
| -rw-r--r-- | basebmp/inc/metafunctions.hxx | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/basebmp/inc/metafunctions.hxx b/basebmp/inc/metafunctions.hxx index 16ee2615f4d7..4e6efb44413f 100644 --- a/basebmp/inc/metafunctions.hxx +++ b/basebmp/inc/metafunctions.hxx @@ -25,6 +25,8 @@ #include <vigra/numerictraits.hxx> #include <functional> +#include <limits> +#include <type_traits> namespace basebmp { @@ -207,7 +209,15 @@ template< typename T > inline T shiftLeft( T v, int shift ) /// Shift right for positive shift value, and left otherwise template< typename T > inline T shiftRight( T v, int shift ) { - return shift > 0 ? v >> shift : v << (-shift); + // Avoid undefined behavior and only shift by less than the length in bits + // of the promoted left operand: + static_assert( + std::is_unsigned<T>::value, + "must be unsigned for promotedBits and the below ': 0' to be correct"); + auto const promotedBits = std::numeric_limits<decltype(+T())>::digits; + return shift >= 0 + ? shift < promotedBits ? v >> shift : 0 + : -shift < promotedBits ? v << (-shift) : 0; } } // namespace basebmp |