[英]C# to F# Interop: How to specify a C# method's optional parameter in F# function type signature?
[英]F# interop with C# class that has an optional nullable parameter set to anything but null causes NullReferenceException / AccessViolationException
我有以下C#類
public class BadClass
{
public BadClass(int? bad = 1)
{
}
}
public class GoodClass
{
public GoodClass(int? good = null)
{
}
}
正如您所看到的,它們都具有可選的可空參數作為其構造函數的一部分,唯一的區別是BadClass將參數default設置為null以外的其他值。
如果我嘗試在F#中創建這些類的實例,這就是我得到的:
這很好用:
let g = GoodClass()
這會拋出NullReferenceException:
let b = BadClass()
這會引發AccessViolationException
let asyncB = async { return BadClass() } |> Async.RunSynchronously
知道為什么會這樣嗎?
編輯
使用ILSpy對其進行反編譯,這是F#的輸出
C#類位於一個名為InteopTest的程序集中[原文如此]
ILSpy到C#
GoodClass g = new GoodClass(null);
BadClass b = new BadClass(1);
FSharpAsyncBuilder defaultAsyncBuilder = ExtraTopLevelOperators.DefaultAsyncBuilder;
FSharpAsync<BadClass> fSharpAsync = defaultAsyncBuilder.Delay<BadClass>(new Program.asyncB@10(defaultAsyncBuilder));
FSharpAsync<BadClass> computation = fSharpAsync;
BadClass asyncB = FSharpAsync.RunSynchronously<BadClass>(computation, null, null);
FSharpFunc<string[], Unit> fSharpFunc = ExtraTopLevelOperators.PrintFormatLine<FSharpFunc<string[], Unit>>(new PrintfFormat<FSharpFunc<string[], Unit>, TextWriter, Unit, Unit, string[]>("%A"));
fSharpFunc.Invoke(argv);
return 0;
這就是IL
.method public static
int32 main (
string[] argv
) cil managed
{
.custom instance void [FSharp.Core]Microsoft.FSharp.Core.EntryPointAttribute::.ctor() = (
01 00 00 00
)
// Method begins at RVA 0x2050
// Code size 92 (0x5c)
.maxstack 5
.entrypoint
.locals init (
[0] class [InteopTest]InteopTest.GoodClass g,
[1] valuetype [mscorlib]System.Nullable`1<int32>,
[2] class [InteopTest]InteopTest.BadClass b,
[3] class [InteopTest]InteopTest.BadClass asyncB,
[4] class [FSharp.Core]Microsoft.FSharp.Control.FSharpAsync`1<class [InteopTest]InteopTest.BadClass>,
[5] class [FSharp.Core]Microsoft.FSharp.Control.FSharpAsyncBuilder builder@,
[6] class [FSharp.Core]Microsoft.FSharp.Control.FSharpAsync`1<class [InteopTest]InteopTest.BadClass>,
[7] class [FSharp.Core]Microsoft.FSharp.Core.FSharpFunc`2<string[], class [FSharp.Core]Microsoft.FSharp.Core.Unit>,
[8] string[]
)
IL_0000: nop
IL_0001: ldloca.s 1
IL_0003: initobj valuetype [mscorlib]System.Nullable`1<int32>
IL_0009: ldloc.1
IL_000a: newobj instance void [InteopTest]InteopTest.GoodClass::.ctor(valuetype [mscorlib]System.Nullable`1<int32>)
IL_000f: stloc.0
IL_0010: ldc.i4.1
IL_0011: newobj instance void [InteopTest]InteopTest.BadClass::.ctor(valuetype [mscorlib]System.Nullable`1<int32>)
IL_0016: stloc.2
IL_0017: call class [FSharp.Core]Microsoft.FSharp.Control.FSharpAsyncBuilder [FSharp.Core]Microsoft.FSharp.Core.ExtraTopLevelOperators::get_DefaultAsyncBuilder()
IL_001c: stloc.s builder@
IL_001e: ldloc.s builder@
IL_0020: ldloc.s builder@
IL_0022: newobj instance void Program/asyncB@10::.ctor(class [FSharp.Core]Microsoft.FSharp.Control.FSharpAsyncBuilder)
IL_0027: callvirt instance class [FSharp.Core]Microsoft.FSharp.Control.FSharpAsync`1<!!0> [FSharp.Core]Microsoft.FSharp.Control.FSharpAsyncBuilder::Delay<class [InteopTest]InteopTest.BadClass>(class [FSharp.Core]Microsoft.FSharp.Core.FSharpFunc`2<class [FSharp.Core]Microsoft.FSharp.Core.Unit, class [FSharp.Core]Microsoft.FSharp.Control.FSharpAsync`1<!!0>>)
IL_002c: stloc.s 4
IL_002e: ldloc.s 4
IL_0030: stloc.s 6
IL_0032: ldloc.s 6
IL_0034: ldnull
IL_0035: ldnull
IL_0036: call !!0 [FSharp.Core]Microsoft.FSharp.Control.FSharpAsync::RunSynchronously<class [InteopTest]InteopTest.BadClass>(class [FSharp.Core]Microsoft.FSharp.Control.FSharpAsync`1<!!0>, class [FSharp.Core]Microsoft.FSharp.Core.FSharpOption`1<int32>, class [FSharp.Core]Microsoft.FSharp.Core.FSharpOption`1<valuetype [mscorlib]System.Threading.CancellationToken>)
IL_003b: stloc.3
IL_003c: ldstr "%A"
IL_0041: newobj instance void class [FSharp.Core]Microsoft.FSharp.Core.PrintfFormat`5<class [FSharp.Core]Microsoft.FSharp.Core.FSharpFunc`2<string[], class [FSharp.Core]Microsoft.FSharp.Core.Unit>, class [mscorlib]System.IO.TextWriter, class [FSharp.Core]Microsoft.FSharp.Core.Unit, class [FSharp.Core]Microsoft.FSharp.Core.Unit, string[]>::.ctor(string)
IL_0046: call !!0 [FSharp.Core]Microsoft.FSharp.Core.ExtraTopLevelOperators::PrintFormatLine<class [FSharp.Core]Microsoft.FSharp.Core.FSharpFunc`2<string[], class [FSharp.Core]Microsoft.FSharp.Core.Unit>>(class [FSharp.Core]Microsoft.FSharp.Core.PrintfFormat`4<!!0, class [mscorlib]System.IO.TextWriter, class [FSharp.Core]Microsoft.FSharp.Core.Unit, class [FSharp.Core]Microsoft.FSharp.Core.Unit>)
IL_004b: stloc.s 7
IL_004d: ldarg.0
IL_004e: stloc.s 8
IL_0050: ldloc.s 7
IL_0052: ldloc.s 8
IL_0054: callvirt instance !1 class [FSharp.Core]Microsoft.FSharp.Core.FSharpFunc`2<string[], class [FSharp.Core]Microsoft.FSharp.Core.Unit>::Invoke(!0)
IL_0059: pop
IL_005a: ldc.i4.0
IL_005b: ret
} // end of method Program::main
對我來說,這看起來像是F#編譯器中的一個錯誤。 如果你寫一些額外的C#:
public class OtherClass
{
private static BadClass _bc = new BadClass();
}
看看IL,你會看到這個:
// push 1 on the stack
IL_0000: ldc.i4.1
// call Nullable<int32> constructor, leaving object on stack
IL_0001: newobj instance void valuetype [mscorlib]System.Nullable`1<int32>::.ctor(!0)
// call BadClass constructor with int?
IL_0006: newobj instance void Nullabool.BadClass::.ctor(valuetype [mscorlib]System.Nullable`1<int32>)
// store in _bc
IL_000b: stsfld class Nullabool.BadClass Nullabool.OtherClass::_bc
其中明確地將Nullable`1實例化為1。
而b的F#代碼最終會像這樣:
// push a 1 on the stack
IL_0016: ldc.i4.1
// call BadClass constructor with 1 - this fails IL verification
IL_0017: newobj instance void [Nullabool]Nullabool.BadClass::.ctor(valuetype [mscorlib]System.Nullable`1<int32>)
哪個在堆棧上留下一個int
而不是int?
。 當我嘗試運行此代碼時,由於類型不匹配,我收到IL驗證錯誤。
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.