compiler-warning-c4439.md

description	title	ms.date	f1_keywords	helpviewer_keywords
Learn more about: Compiler Warning (level 1, error) C4439	Compiler warning (level 1, error) C4439	1/22/2025	C4439	C4439

Compiler warning C4439

'function name': function definition with a managed type in the signature must have a __clrcall calling convention

The compiler implicitly replaced a calling convention with __clrcall. To resolve this warning, remove the __cdecl or __stdcall calling convention.

C4439 is always issued as an error. You can turn off this warning with the #pragma warning or /wd. For more information, see warning or /w, /W0, /W1, /W2, /W3, /W4, /w1, /w2, /w3, /w4, /Wall, /wd, /we, /wo, /Wv, /WX (Warning Level).

Example

The following sample generates C4439:

// C4439.cpp
// compile with: /clr
void __stdcall f( System::String^ arg ) {}   // C4439
void __clrcall f2( System::String^ arg ) {}   // OK
void f3( System::String^ arg ) {}   // OK