正如标题所说,我知道 new 抛出一个可以被捕获的异常,但是指针到底发生了什么?它变成NULL?我检查了一些关于 SO 的答案,但没有人解释它。检查下面的示例,指针保持在堆上?请提供有关此模式的完整信息
#include <windows.h>
#include <cstdlib>
#include <iostream>
using namespace std;
enum eReadMode
{
// READ_ONLY,
READ_WRITE,
// CREATE_FILE,
// CREATE_WRITE_FILE,
};
class CFileStatic
{
private:
FILE *m_File;
public:
CFileStatic( LPCTSTR szFileName, eReadMode eMode );
virtual ~CFileStatic() {};
bool IsValidFile() const { return( m_File != NULL ); };
void PrintFile( unsigned int uLine = 0 );
};
CFileStatic::CFileStatic( LPCTSTR szFileName, eReadMode eMode )
{
if( szFileName )
{
if( eMode == READ_WRITE )
m_File = fopen( szFileName, "r+" );
else
printf( "Valid usage of: READ_WRITE only" );
}
else
m_File = NULL;
}
void CFileStatic::PrintFile( unsigned int uLine )
{
static unsigned uFindNumber;
if( uLine == 0 )
{
char szBuffer[1024];
while( fgets( szBuffer, 1024, m_File ) )
{
std::cout << szBuffer;
}
}
else
{
char szBuffer[1024];
while( fgets( szBuffer, 1024, m_File ) )
{
uFindNumber++;
if( uFindNumber == uLine )
{
std::cout << szBuffer;
}
}
}
}
int main( int argc, char *argv[] )
{
//if new fails, what 'pFile' turns out to be? and do I need to delete
//it later?
CFileStatic *pFile = new CFileStatic( "Console.h", READ_WRITE );
if( pFile->IsValidFile() )
{
pFile->PrintFile(2);
}
CFileStatic *pConsoleCpp = new CFileStatic( "Console.cpp", READ_WRITE );
if( pConsoleCpp->IsValidFile() )
{
pConsoleCpp->PrintFile();
}
system("pause>nul");
return EXIT_SUCCESS;
}