Smart converter error cannot convert6/27/2023 The C2440 errors on lines 15 and 16 of the next sample are qualified with the Incompatible calling conventions for UDT return value message. Return static_cast(d) // error C2440: 'static_cast' : cannot convert from 'Derived *' to 'Base *' Struct Derived // Forward declaration, not defined This sample generates C2440: // c2440a.cpp The compiler emits C2440 if you attempt to cast from a type that's only forward declared but not defined. The next sample generates C2440: // C2440.cpp You may see C2440 if you attempt to convert a pointer to member to void*. reinterpret_cast, C-style cast or function-style cast)Ĭonst char* s1 = u8"test" // C2440 under /std:c++20 or /Zc:char8_t, OK in C++17Ĭonst char8_t* s2 = u8"test" // OK under /std:c++20 or /Zc:char8_t, C4430 in C++17Ĭonst char* s3 = reinterpret_cast(u8"test") // OK note: Types pointed to are unrelated conversion requires ![]() error C2440: 'initializing' : cannot convert from 'const char8_t ' This sample shows how compiler behavior changes between C++17 and C++20: // C2440u8.cpp In C++20 or under /Zc:char8_t, a UTF-8 literal character or string (such as u8'a' or u8"String") is of type const char8_t or const char8_t, respectively. ![]() Conversion from string literal loses const qualifier (see error C2440: 'initializing' : cannot convert from 'const char ' Build: cl /Zc:strictStrings /W3 C2440s.cpp This sample generates C2440: // C2440s.cpp In C, the type of a string literal is array of char, but in C++, it's array of const char. ![]() Examples C++ string literals are constĬ2440 can be caused if you attempt to initialize a non-const char* (or wchar_t*) by using a string literal in C++ code, when the compiler conformance option /Zc:strictStrings is set. We've listed some common ones in the Examples section. There are many ways to generate this error. The compiler generates C2440 when it can't convert from one type to another, either implicitly or by using the specified cast or conversion operator. The compiler can't implicitly convert from *type1* to *type2*, or can't use the specified cast or conversion operator. ' conversion' : cannot convert from ' type1' to ' type2' ' initializing' : cannot convert from ' type1' to ' type2'
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