[英]C++ can't delete char*, keeps corrupting heap
語言:C ++,編譯器:MSVS(/ Za)和g ++(是的,必須同時運行),級別:初學者
我試圖從char *中刪除數據,以便重新分配它並繼續執行程序。 我創建了一個新的char *,為其分配了命令行參數的值,進行了一些驗證,然后,如果驗證失敗,則應取消分配char *,然后讓我將新數據分配給var,但是我得到了“堆” Visual Studio中檢測到損壞”錯誤。 我對當前代碼的修復以及可以更清楚/簡潔地完成此操作的任何其他方式感到好奇。
在main()中:
//...
//make non constant versions to be messed with
char* ba = new char[ strlen(argv[4]) + 1 ];
char* num = new char[ strlen(argv[2]) + 1 ];
//make non constant versions of commandline stuff
nonConstant( argv[4], argv[2], ba, num );
//do the conversion and printing
convert( ba, num );
//...
轉換執行此操作:
//...
if( error ) {
getNew(ba, num, &error);
}
//...
這是getNew:
void getNew( char* ba, char* num, bool error ) {
//if there's an error in their numbers let them input new stuff and check to see if that's valid
while( error ) {
//tell the user that the input was bad an prompt for more, use getline because strings are weird
//cin stuff here (this part works, no problems)
//free up base and num so I can reassign them
delete[] ba; //<--this line fails
delete[] num;
//set lengths = to lengths of input + 1 for \0
ba = new char[ inputBa.length() + 1 ];
num = new char[ inputNum.length() + 1 ];
//do the assignment of new input back to base and num
inputBa.copy( ba, inputBa.length(), 0 );
inputNum.copy( num, inputNum.length(), 0 );
//ensure that the input was good this time
validateInput( ba, num, error );
}
停 ! 立即切換到std::string
。
這將修復您的代碼,並根據要求使其更加清晰/簡潔。
如果您的getNew
函數可以重新分配本地ba
和num
所指向的內存,即再次delete[]
和new[]
進行分配。
但是,在convert
中,調用ba
和num
呢? 另外, main
ba
和num
呢? 它們按值傳遞給getNew
,這意味着它們保持不變。 它們繼續指向其原始(現已失效)的存儲位置。 我猜想您會繼續在convert
和main
使用那些現在毫無意義的ba
和num
值,直到它們導致崩潰。 例如,如果您getNew
使用這些舊指針值調用getNew
,則getNew
可能會在delete[]
失敗。
同樣,還不能立即知道convert
什么error
。 當getNew
實際上需要一個bool
參數時,為什么將它作為&error
(可能是一個指針) getNew
呢? 它將編譯,但無論如何看起來還是一個問題。
通過char *&傳遞參數將解決此問題。
#include <stdio.h>
#include <string.h>
void reassgnReference( char * &ba, char * &num );
void reassgnPointerToPointer( char ** ba, char ** num );
int main( int argc, char ** argv )
{
if ( argc > 4 )
{
char * ba = new char[strlen( argv[ 4 ] ) + 1];
char * num = new char[strlen( argv[ 2 ] ) + 1];
strncpy( ba, argv[ 4 ], strlen( argv[ 4 ] ) );
strncpy( num, argv[ 2 ], strlen( argv[ 2 ] ) );
printf( "In the beginning, ba = %s, num = %s\n", ba, num );
reassgnReference( ba, num );
printf( "reassgnReference(), ba = %s, num = %s\n", ba, num );
reassgnPointerToPointer( &ba, &num );
printf( "reassgnPointerToPointer(), ba = %s, num = %s\n", ba, num );
}
else
{
printf( "%s Expects at least 4 arguments\n", argv[ 0 ] );
}
return( 0 );
}
void reassgnReference( char *& ba, char *& num )
{
delete[] ba;
delete[] num;
char const * const newBa = "ba from reference";
char const * const newNum = "num from reference";
ba = new char[strlen( newBa ) + 1];
num = new char[strlen( newNum ) + 1];
strncpy( ba, newBa, strlen( newBa ) );
strncpy( num, newNum, strlen( newNum ) );
}
void reassgnPointerToPointer( char ** ba, char ** num )
{
delete[] *ba;
delete[] *num;
char const * const newBa = "ba from pointer to pointer";
char const * const newNum = "num from pointer to pointer";
*ba = new char[strlen( newBa ) + 1];
*num = new char[strlen( newNum ) + 1];
strncpy( *ba, newBa, strlen( newBa ) );
strncpy( *num, newNum, strlen( newNum ) );
}
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