更大尺寸的strcpy崩溃（iPhone使用rapidXML）

Question

我正在关注iOS5上的rapidxml教程，不幸的是我的c有点生疏。下面的代码适用于较小的字符大小，但当我拉下较大的大小时，我会使用

EXC_BAD_ACCESS

崩溃（我正在从RESTful接口中提取XML）。

# pragma mark - parser methods
-(void)parseIncomingFeed:(NSData *)xmlData:(NSString*)tag {

    NSString *xmlStringOrg = [[NSString alloc] initWithData:xmlData encoding:NSASCIIStringEncoding];
    NSLog(@"[xmlStringOrg length] = %-10d  [xmlData length] = %d", [xmlStringOrg length],[xmlData length]);
    char xmlString[[xmlStringOrg length]];
    strcpy(xmlString, [xmlStringOrg UTF8String]);  // <--- crashes here
    ...

以下是结果：

[xmlStringOrg length] = 13580       [xmlData length] = 13580
[xmlStringOrg length] = 115476      [xmlData length] = 115476
[xmlStringOrg length] = 154589      [xmlData length] = 154589
[xmlStringOrg length] = 1902        [xmlData length] = 1902
[xmlStringOrg length] = 23402       [xmlData length] = 23402
[xmlStringOrg length] = 93037       [xmlData length] = 93037
[xmlStringOrg length] = 1723        [xmlData length] = 1723
[xmlStringOrg length] = 172329      [xmlData length] = 172329
[xmlStringOrg length] = 3470671     [xmlData length] = 3470671

(boom! with EXE_BAD_ACCESS leading to:  0x3234af6e:  push.w {r3, r4})

盲目地，我尝试了以下但没有运气：

 NSString *xmlStringOrg = [[NSString alloc] initWithData:xmlData encoding:NSASCIIStringEncoding];
 char xmlString[3600000];
 strcpy(xmlString, [xmlStringOrg UTF8String]);

和

 NSString *xmlStringOrg = [[NSString alloc] initWithData:xmlData encoding:NSASCIIStringEncoding];
 char xmlString[[xmlStringOrg length]];
 strncpy(xmlString, [xmlStringOrg UTF8String], [xmlStringOrg length]);

有什么想法吗？从很久以前的c类开始，感觉就像我需要大小超过X的块大小并单独处理它们但是我不知道从哪里开始.R

编辑1 - 工作

感谢@ RichardJ.RossIII，以下作品：

# pragma mark - parser methods
-(void)parseIncomingFeed:(NSData *)xmlData:(NSString*)tag {

    NSString *xmlStringOrg = [[NSString alloc] initWithData:xmlData encoding:NSASCIIStringEncoding];
    NSLog(@"[xmlStringOrg length] = %-10d  [xmlData length] = %d", [xmlStringOrg length],[xmlData length]);
    char *xmlString = (char*) malloc([xmlStringOrg length]);
    strcpy(xmlString, [xmlStringOrg UTF8String]);  // no more tears
    ...
    free(xmlString);
  }