動作環境

RAD Studio 10.2 Tokyo Update 2

c++ builder XE4 > エラー > 長すぎたため切り捨てられた行があります。. > 3200文字はだめ > 文字列リテラル255文字制限

XE4では255文字での制限がかかっていた。

10.2 Tokyo + Windows 10 Proだとどうなるか試した。
3500程度の文字列をstatic const Stringで定義してみたが、問題なかった。
TMemoに代入して、クリップボードにコピーする処理で問題がなかった。

Unit1.cpp

//---------------------------------------------------------------------------

#include <vcl.h>
#pragma hdrstop

#include "Unit1.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------

static const String kDummyText =
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"

"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"

"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"

"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"

"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"

"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"

"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
"1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890""1234567890"
;

__fastcall TForm1::TForm1(TComponent* Owner)
	: TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
	ShowMessage(kDummyText);

	Memo1->Lines->Add(kDummyText);

	Memo1->SelectAll();
    Memo1->CopyToClipboard();
}