I'm using C Builder XE6 and wrote the following Delphi unit:

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.

When compiled, the following .hpp file is generated:

// 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

Note that the default value of Infinity in the .pas file is translated to INF in the .hpp file.

When I include the .hpp file in a C unit, I get the following compiler error:

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

Understandable, because INF is not defined in System.Math.hpp, but Infinity is.

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

CodePudding user response：

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

AFAIK, you don't. That is simply how the Delphi compiler chose to translate Infinity for C . Feel free to submit a bug report to Embarcadero about it.

In the meantime, as a workaround, what you could try instead is declaring GetJSONDouble with {$NODEFINE} or {$EXTERNALSYM} to avoid the Delphi compiler from outputting a default declaration in the .hpp, and then use {$HPPEMIT} to declare GetJSONDouble() yourself, eg:

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.