如何防止 strncpy_s 在调试版本中填充目标缓冲区? [英] How can I prevent strncpy_s from padding destination buffer in debug build?

问题描述

我维护了一段相当大的遗留代码，这些代码仍然大量使用 strncpy.我现在已经开始将 strncpy 的用法替换为其安全对应物 strncpy_s 的过程.我注意到 strncpy_s 正在用 -2 值填充目标缓冲区 - 但仅在调试版本中！在发布版本中不发生填充.

例如:

字符缓冲区[3];//缓冲区变为 00000000 00000000 00000000memset(buffer, 0, sizeof(buffer));//缓冲区变为 01100001 00000000 11111110//97 ('a') 0 -2strncpy_s(buffer, sizeof(buffer), "a", _TRUNCATE);//我是-2int i = 缓冲区[2];

MSDN 文档 没有提到这种填充行为，并且在我的情况确实是我不想要的东西，因为我的遗留代码依赖于这样一个事实，即缓冲区的归零部分保持归零并且在字符串复制期间不会被覆盖.

有什么方法可以防止 strncpy_s 在调试版本中填充目标字符串?

请注意，我已使用 Visual Studio 2010 和 Visual Studio 2013 对此进行了测试.

解决方案

strcpy_s() 只会在调试模式下用 'FE' 填充缓冲区.

您可以通过调用 _CrtSetDebugFillThreshold(0)

来明确关闭此功能

I maintain a fairly large piece of legacy code that still uses strncpy a lot. I have now started the process of replacing the usage of strncpy with its safe counterpart strncpy_s. I noticed that strncpy_s is padding the destination buffer with -2 values - but only in debug builds! In release builds no padding occurs.

For instance:

char buffer[3];
// buffer becomes 00000000  00000000  00000000
memset(buffer, 0, sizeof(buffer));
// buffer becomes 01100001  00000000  11111110
//                97 ('a')  0        -2
strncpy_s(buffer, sizeof(buffer), "a", _TRUNCATE);
// i is -2
int i = buffer[2];

The MSDN docs do not mention this padding behaviour, and in my case it's really something I don't want because my legacy code relies on the fact that the zeroed parts of the buffer remain zeroed and are not overwritten during string copying.

Is there a way how I can prevent strncpy_s from padding the destination string in debug builds?

Note that I have tested this with both Visual Studio 2010 and Visual Studio 2013.

解决方案

strcpy_s() will fill in the buffer with 'FE' in debug mode only.

You can turn this off explicitly by calling _CrtSetDebugFillThreshold(0)

这篇关于如何防止 strncpy_s 在调试版本中填充目标缓冲区?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！