Delphi 单位中的无穷大在 .hpp 文件中转换为 +INF

Infinity in Delphi unit is translated to +INF in .hpp file

我正在使用 C++Builder XE6 并编写了以下 Delphi 单元:

unit JSONUtils;

interface

uses
  System.JSON, System.Math;

function GetJSONDouble (Value: TJSONValue; Path: string; Default: Double = Infinity): Double;

implementation

function GetJSONDouble (Value: TJSONValue; Path: string; Default: Double): Double;
begin
  Result := Value.GetValue<Double>(Path, Default);
end;

end.

编译后生成如下.hpp文件:

// CodeGear C++Builder
// Copyright (c) 1995, 2014 by Embarcadero Technologies, Inc.
// All rights reserved

// (DO NOT EDIT: machine generated header) 'JSONUtils.pas' rev: 27.00 (Windows)

#ifndef JsonutilsHPP
#define JsonutilsHPP

#pragma delphiheader begin
#pragma option push
#pragma option -w-      // All warnings off
#pragma option -Vx      // Zero-length empty class member 
#pragma pack(push,8)
#include <System.hpp>   // Pascal unit
#include <SysInit.hpp>  // Pascal unit
#include <System.JSON.hpp>  // Pascal unit
#include <System.Math.hpp>  // Pascal unit

//-- user supplied -----------------------------------------------------------

namespace Jsonutils
{
//-- type declarations -------------------------------------------------------
//-- var, const, procedure ---------------------------------------------------
extern DELPHI_PACKAGE double __fastcall GetJSONDouble(System::Json::TJSONValue* Value, System::UnicodeString Path, double Default = +INF);
}   /* namespace Jsonutils */
#if !defined(DELPHIHEADER_NO_IMPLICIT_NAMESPACE_USE) && !defined(NO_USING_NAMESPACE_JSONUTILS)
using namespace Jsonutils;
#endif
#pragma pack(pop)
#pragma option pop

#pragma delphiheader end.
//-- end unit ----------------------------------------------------------------
#endif  // JsonutilsHPP

请注意,.pas 文件中 Infinity 的默认值在 .hpp 文件中转换为 +INF

当我在 C++ 单元中包含 .hpp 文件时,出现以下编译器错误:

[bcc32 Error] JSONUtils.hpp(26): E2451 Undefined symbol 'INF'

可以理解,因为INFSystem.Math.hpp中没有定义,而Infinity是。

如何让编译器将 Infinity(或 HUGE_VAL)输出到 .hpp 文件而不是 +INF

How do I get the compiler to output Infinity (or HUGE_VAL) to the .hpp file instead of +INF?

AFAIK,你不知道。这就是 Delphi 编译器选择为 C++ 翻译 Infinity 的方式。随意 submit a bug report to Embarcadero 关于它。

同时,作为一种解决方法,您可以尝试用 {$NODEFINE} or {$EXTERNALSYM} to avoid the Delphi compiler from outputting a default declaration in the .hpp, and then use {$HPPEMIT} 声明 GetJSONDouble 来自己声明 GetJSONDouble(),例如:

unit JSONUtils;

interface

uses
  System.JSON, System.Math;

{$EXTERNALSYM GetJSONDouble}
function GetJSONDouble (Value: TJSONValue; Path: string; Default: Double = Infinity): Double;

{$HPPEMIT OPENNAMESPACE}
{$HPPEMIT 'extern DELPHI_PACKAGE double __fastcall GetJSONDouble(System::Json::TJSONValue* Value, System::UnicodeString Path, double Default = System::Math::Infinity);'}
{$HPPEMIT CLOSENAMESPACE}

implementation

function GetJSONDouble (Value: TJSONValue; Path: string; Default: Double): Double;
begin
  Result := Value.GetValue<Double>(Path, Default);
end;

end.