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Untangle cast logic to not implicitly require castability (#1442)

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The current code requires implicitly that integral types are cast-able to floating point. In case of strongly-typed integrals (e.g. as explained at http://www.ilikebigbits.com/blog/2014/5/6/type-safe-identifiers-in-c) this is not always the case.

This commit uses SFINAE to move the numeric conversions into separate `cast()` implementations to avoid the issue.
This commit is contained in:
Dennis Luxen 2018-07-17 15:48:51 +02:00 committed by Jason Rhinelander
parent 534b756cb3
commit 221fb1e11e
1 changed files with 29 additions and 15 deletions
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44
include/pybind11/cast.h
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@ -17,6 +17,7 @@
#include <array> #include <array>
#include <limits> #include <limits>
#include <tuple> #include <tuple>
#include <type_traits>
#if defined(PYBIND11_CPP17) #if defined(PYBIND11_CPP17)
# if defined(__has_include) # if defined(__has_include)
@ -1009,21 +1010,34 @@ public:
return true; return true;
} }
static handle cast(T src, return_value_policy /* policy */, handle /* parent */) { template<typename U = T>
if (std::is_floating_point<T>::value) { static typename std::enable_if<std::is_floating_point<U>::value, handle>::type
return PyFloat_FromDouble((double) src); cast(U src, return_value_policy /* policy */, handle /* parent */) {
} else if (sizeof(T) <= sizeof(ssize_t)) { return PyFloat_FromDouble((double) src);
// This returns a long automatically if needed }
if (std::is_signed<T>::value)
return PYBIND11_LONG_FROM_SIGNED(src); template<typename U = T>
else static typename std::enable_if<!std::is_floating_point<U>::value && std::is_signed<U>::value && (sizeof(U) <= sizeof(long)), handle>::type
return PYBIND11_LONG_FROM_UNSIGNED(src); cast(U src, return_value_policy /* policy */, handle /* parent */) {
} else { return PYBIND11_LONG_FROM_SIGNED((long) src);
if (std::is_signed<T>::value) }
return PyLong_FromLongLong((long long) src);
else template<typename U = T>
return PyLong_FromUnsignedLongLong((unsigned long long) src); static typename std::enable_if<!std::is_floating_point<U>::value && std::is_unsigned<U>::value && (sizeof(U) <= sizeof(unsigned long)), handle>::type
} cast(U src, return_value_policy /* policy */, handle /* parent */) {
return PYBIND11_LONG_FROM_UNSIGNED((unsigned long) src);
}
template<typename U = T>
static typename std::enable_if<!std::is_floating_point<U>::value && std::is_signed<U>::value && (sizeof(U) > sizeof(long)), handle>::type
cast(U src, return_value_policy /* policy */, handle /* parent */) {
return PyLong_FromLongLong((long long) src);
}
template<typename U = T>
static typename std::enable_if<!std::is_floating_point<U>::value && std::is_unsigned<U>::value && (sizeof(U) > sizeof(unsigned long)), handle>::type
cast(U src, return_value_policy /* policy */, handle /* parent */) {
return PyLong_FromUnsignedLongLong((unsigned long long) src);
} }
PYBIND11_TYPE_CASTER(T, _<std::is_integral<T>::value>("int", "float")); PYBIND11_TYPE_CASTER(T, _<std::is_integral<T>::value>("int", "float"));