entityMap|blocks|key|cf94e|text|if+(c+=+1)+//+insert+code+here|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript^0^^$0|$]|1|@$2|3|4|5|6|7|8|E|9|@]|A|@]|B|$C|D]]]]

<pre><code>if (c = 1) // insert code here
</code></pre>

entityMap|blocks|key|blfqf|text|for(int+i+=+0;+i<10;+%2B%2Bi)
++//code+here
++//code+added+later|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|dqall|请注意，稍后添加的代码不在for循环中。|unstyled^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|H|9|@]|A|@]|B|$C|D]]|$2|E|4|F|6|G|8|I|9|@]|A|@]|B|$]]]]

<pre><code>for(int i = 0; i&lt;10; ++i)
 //code here
 //code added later
</code></pre>

Note that the later added code is not in the for loop.

entityMap|blocks|key|56o18|text|需要注意的一件事是数组界限。如果你越界了，如果运气不好，你最终可能会覆盖用于其他数据的内存。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|a08ed|与此相关的一个令人讨厌的错误是函数中的静态数组变量越界。这最终成为了一个函数，它改变了调用函数的局部变量的值。这并不是很直接的调试..^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|E|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|F|9|@]|A|@]|B|$]]]]

One thing to look after are array bounds. If you go out of bounds, with bad luck you may end up overwriting memory that is used for other data.

One nasty bug related to this was going out of bounds for a static array variable in a function. That ended up as a function changing values of the local variables of the calling function. That wasn't so straight-forward to debug..

entityMap|blocks|key|bd9gb|text|几年前，我接到前同事的电话，告诉我他必须解决我的代码的问题，我的代码是信用卡交易的路由器。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|9kvhu|卡号前缀由6位BIN+(银行识别码)和银行自行决定使用的额外几位数字组成，例如银行为Visa+Classic卡456789预留BIN，并预留2位额外数字表示子产品，如01表示学生卡，02表示与当地百货商店的联合品牌卡等。在这种情况下，基本上是产品标识符的卡片前缀变成了8位数的长度。当我编写这部分代码时，我决定9位数字“对每个人来说都应该足够了”。它运行了两年，直到有一天银行制造了一个新的10位数前缀的卡产品(不知道他们为什么需要它)。不难想象发生了什么-路由器分段故障，整个系统因为没有交易路由器而无法工作，该银行(全国最大的银行之一)的所有自动取款机都在几个小时内无法操作，直到问题被发现和解决。|6o6an|我不能在这里发布代码，首先是因为我没有它，其次是它是公司的版权，但不难想象|3l667|而不检查目标缓冲区的大小。|c9ei0|就像|3h677|说：|5er30|如果strcpy()的目标字符串不够大(也就是说，如果程序员很愚蠢或懒惰，并且在复制之前没有检查大小)，那么可能会发生任何事情。溢出固定长度字符串是一种最受欢迎的破解技术。|aq0lh|4372m|我很尴尬。但我已经吸取了教训，不要忘记(通常是:)检查目标缓冲区的大小。我不建议你通过困难的方式来学习它--只需要养成在检查目标缓冲区之前检查一下目标缓冲区的习惯就行了。|423rh|和|6v7s8|..。|ehfm9|编辑:来自Healthcarel的好建议-使用|7pel2|而不是|vq37|..。它没有添加尾随的0，但我通常使用下面的宏来绕过它：^0|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|11|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|12|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|13|9|@]|A|@]|B|$]]|$2|G|4|H|6|7|8|14|9|@]|A|@]|B|$]]|$2|I|4|J|6|7|8|15|9|@]|A|@]|B|$]]|$2|K|4|L|6|7|8|16|9|@]|A|@]|B|$]]|$2|M|4|N|6|7|8|17|9|@]|A|@]|B|$]]|$2|O|4|-4|6|7|8|18|9|@]|A|@]|B|$]]|$2|P|4|Q|6|7|8|19|9|@]|A|@]|B|$]]|$2|R|4|S|6|7|8|1A|9|@]|A|@]|B|$]]|$2|T|4|U|6|7|8|1B|9|@]|A|@]|B|$]]|$2|V|4|W|6|7|8|1C|9|@]|A|@]|B|$]]|$2|X|4|Y|6|7|8|1D|9|@]|A|@]|B|$]]|$2|Z|4|10|6|7|8|1E|9|@]|A|@]|B|$]]]]

Few years ago I've got a call from my ex-colleague telling me about the problem he had to fix with my code, which was a router for credit card transactions.
Card number prefix consists of 6-digit BIN (Bank Identification Number) and extra few digits that banks use at own discretion, e.g. bank has BIN for Visa Classic card 456789, and reserve 2 extra digits to indicate sub-product, like 01 for student's card, 02 for co-branded card with local department store and so on. In this case card prefix, which is basically product identifier, becomes 8 digits long. When I coded this part, I decided that 9 digits &quot;ought to be enough for everyone&quot;. It was running ok for 2 years until one day bank make a new card products with 10-digit-long prefix (have no idea why they needed it). Not too hard to imagine what has happened - router segfaulted, the whole system halted because it cannot function without transaction router, all ATMs of that bank (one of the biggest in the country) became non-operational for few hours, until problem was found and fixed.
I cannot post the code here firstly because I don't have it and secondly it is copyrighted by the company, but it is not hard to imagine the <code>strcpy()</code> without checking size of target buffer.
Just like <code>man strcpy</code> says:
<blockquote>
If the destination string of a
strcpy() is not large enough (that
is, if the programmer was stupid
or lazy, and failed to check the size
before copying) then anything might
happen. Overflowing fixed length
strings is a favorite cracker
technique.
</blockquote>
I was very embarrassed. But I've learned the lesson and do not forget (usually :) ) to check size of target buffer. I wouldn't recommend you to learn it the hard way - just develop a habit to check target buffer before <code>strcpy()</code> and <code>strcat()</code>.
Edit: good suggestion from Healthcarel - use <code>strncpy()</code> rather than <code>strcpy()</code>. It doesn't add trailing 0 but I usually use following macro to get around it:
<code>#define STRNCPY(A,B,C) do {strncpy(A,B,C); A[C] = 0; } while (0)</code>

entityMap|blocks|key|89rul|text|已经很长一段时间了，但有些事情你永远不会忘记;-)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|79jc0|忘了|6ibpt|在字符串的末尾。|947c9|为n个字符的字符串分配n个字符。|cdbi8|忘记了switch语句中的中断符。|2cqtt|“创造性”宏用法。^0|0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|M|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|N|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|O|9|@]|A|@]|B|$]]|$2|G|4|H|6|7|8|P|9|@]|A|@]|B|$]]|$2|I|4|J|6|7|8|Q|9|@]|A|@]|B|$]]|$2|K|4|L|6|7|8|R|9|@]|A|@]|B|$]]]]

It has been a long time, but some things you never forget ;-).

<ul>
<li>forget the <code>\0</code> at the end of a string.</li>
<li>allocate n characters for a string with n characters.</li>
<li>forgetting the break in a switch statement.</li>
<li>'creative' macro use.</li>
</ul>

entityMap|blocks|key|b50kk|text|使用不受限制的字符串函数，如strcpy()或strcmp()，而不是安全版本，如strncpy()和strncmp()。|type|unstyled|depth|inlineStyleRanges|entityRanges|data^0^^$0|$]|1|@$2|3|4|5|6|7|8|C|9|@]|A|@]|B|$]]]]

Using non-limited string functions such as strcpy() or strcmp(), instead of safe versions like strncpy() and strncmp().

entityMap|blocks|key|264gi|text|将虚拟地址传递给DMA引擎是最糟糕的，与C语言无关，但我假设99%25的DMA相关内容都是用C编写的，所以这是一种匹配。这个小错误导致内存崩溃，我花了1.5个月才找到它。|type|unstyled|depth|inlineStyleRanges|entityRanges|data^0^^$0|$]|1|@$2|3|4|5|6|7|8|C|9|@]|A|@]|B|$]]]]

Passing virtual address to the DMA engine was a worst one, not exactly C related, but i assume that 99% of DMA related stuff written in C so it's kind of match. 
This small error lead to memory corruption that took me 1.5 month to find.

entityMap|blocks|key|5bd2r|text|你应该多担心一些小错误。大的/惊人的错误通常被记录在书中(有为什么它们是糟糕的原因，替代方法等)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|83htv|这些小的设计/编码错误会影响到你，因为它们往往会累积起来。|6o7o|因此，我的建议是尝试阅读Kernighan编写或合著的书籍(“C编程语言”、“编程实践”等)。因为它们充满了常识(对于有经验的C程序员来说很常见)，建议和列出的原则在避免小错误和大错误方面都非常有用。|3ljvq|它们还列出了许多潜在的大错误，因此它们回答了您最初的问题。^0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|I|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|J|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|K|9|@]|A|@]|B|$]]|$2|G|4|H|6|7|8|L|9|@]|A|@]|B|$]]]]

You should worry more about little mistakes. Big/spectacular mistakes are usually documented in books (with reasons why they are bad, alternative approaches etc.).

It's the little design/coding mistakes that get to you, because they tend to add up.

So my advice is to try and read the books Kernighan wrote or co-authored ("The C Programming Language", "Practice of Programming" etc.) because they are full of common-sense (common for experienced C programmers) advice and list principles that are very useful in avoiding both small and big mistakes.

They also list many potential big mistakes, so they answer your initial question.

entityMap|blocks|key|1fm1r|text|if(a+==+true);
{
++//Do+sth+when+it+is+true.+But+it+is+allways+executed.
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|ccjnk|编辑|unstyled|7b91n|：同一错误的另一个变体。|cvpi1|for(i=0;+i^0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|L|9|@]|A|@]|B|$C|D]]|$2|E|4|F|6|G|8|M|9|@]|A|@]|B|$]]|$2|H|4|I|6|G|8|N|9|@]|A|@]|B|$]]|$2|J|4|K|6|7|8|O|9|@]|A|@]|B|$C|D]]]]

<pre><code>if(a == true);
{
 //Do sth when it is true. But it is allways executed.
}
</code></pre>

Edit: Another variant of the same mistake.

<pre><code>for(i=0; i&lt;max_iterations;i++);
{
 //Do sth but unexpectedly only once
}
</code></pre>

entityMap|blocks|key|d0at1|text|我在C语言中做过的最危险的事情就是试图写出管理我自己内存的代码。实际上，这意味着|type|unstyled|depth|inlineStyleRanges|entityRanges|data|a8nuq|我在C语言中做过的最危险的事情就是写C代码|bu7g9|..。(我听说这几天你可以绕过它。臀部的理智。在适当的时候使用这些方法！)|5erv2|我不会编写分页算法--操作系统极客会替我写分页算法。|1n54|我不会编写数据库缓存方案--数据库极客会替我做这件事。|2flmf|我不会构建L2处理器缓存--硬件极客会为我做这件事。|d9h0j|我就是这么做的|c29b7|注释|3c57|管理内存。|ce7ph|其他人为我管理我的记忆--他们比我设计得更好，测试比我更好，代码比我更好，当他们犯了危及安全的关键错误时，他们会打补丁，这些错误只会在10年后才被注意到，因为|8g269|绝对是每个人|4p99|尝试分配内存的人有时会失败。^0|0|0|0|0|0|0|0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|Y|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|Z|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|10|9|@]|A|@]|B|$]]|$2|G|4|H|6|7|8|11|9|@]|A|@]|B|$]]|$2|I|4|J|6|7|8|12|9|@]|A|@]|B|$]]|$2|K|4|L|6|7|8|13|9|@]|A|@]|B|$]]|$2|M|4|N|6|7|8|14|9|@]|A|@]|B|$]]|$2|O|4|P|6|7|8|15|9|@]|A|@]|B|$]]|$2|Q|4|R|6|7|8|16|9|@]|A|@]|B|$]]|$2|S|4|T|6|7|8|17|9|@]|A|@]|B|$]]|$2|U|4|V|6|7|8|18|9|@]|A|@]|B|$]]|$2|W|4|X|6|7|8|19|9|@]|A|@]|B|$]]]]

The most dangerous thing I ever did in C was trying to write code which managed my own memory. Effectively, this means the most dangerous thing I ever did in C was write C code. (I hear that you can get around it these days. Hip hip for sanity. Use those approaches whenever appropriate!)

<ul>
<li>I don't write paging algorithms -- OS geeks do that for me.</li>
<li>I don't write database caching schemes -- database geeks do that for me.</li>
<li>I don't build L2 processor caches -- hardware geeks do that for me.</li>
</ul>

And I do not manage memory. 

Someone else manages my memory for me -- someone who can design better than I can, and test better than I can, and code better than I can, and patch when they make critical security-compromising mistakes which only get noticed 10 years later because absolutely everyone who attempts to allocate memory fails some of the time.

entityMap|blocks|key|eajg3|text|​|type|unstyled|depth|inlineStyleRanges|entityRanges|data|airii|第一次分配指针时，它没有指针对象。|bn61l|指针“未初始化”|7slcg|对错误指针的解引用操作是一个严重的运行时错误。|ec81d|如果幸运的话，取消引用操作将立即崩溃或停止(Java就是这样的)。|1c8ld|如果你不走运，错误的指针取消引用将破坏随机的内存区域，稍微改变程序的操作，使其在一段不确定的时间后出错。必须为每个指针分配一个指针对象，然后才能支持取消引用操作。^0|0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|M|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|N|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|O|9|@]|A|@]|B|$]]|$2|G|4|H|6|7|8|P|9|@]|A|@]|B|$]]|$2|I|4|J|6|7|8|Q|9|@]|A|@]|B|$]]|$2|K|4|L|6|7|8|R|9|@]|A|@]|B|$]]]]

When a pointer is first allocated, it does not have a pointee. 
The pointer is "uninitialized"
A dereference operation on a bad pointer is a serious runtime error.
If you are lucky, the dereference operation will crash or halt immediately (Java behaves this
way). If you are unlucky, the bad pointer dereference will corrupt a random area of
memory, slightly altering the operation of the program so that it goes wrong some
indefinite time later. Each pointer must be assigned a pointee before it can support
dereference operations.

entityMap|blocks|key|8uhma|text|我将危险的定义理解为“我们可能会发布这个bug，直到几年后才发现它已经太晚了”：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|9mi8e|char*+c+=+malloc(...);
.
.
.
free(c);++
.
.
.
c[...]+=+...;|code-block|syntax|javascript|1r5ne|或者|218s5|//+char*+s+is+an+input+string
char*+c+=+malloc(strlen(s));
strcpy(c,+s);|86aau|但是如果你写的是多平台的(不限于x86/x64)，这也是很棒的：|9nf6n|char*+c+=+...;
int+i+=+*((int*)c);+//+<--+alignment+fault|ddcaf|如果您的缓冲区来自不受信任的来源..基本上，周围的大多数代码都是危险的。|2al0u|但是，不管怎样，在C语言中，很容易就会击中自己的脚，以至于一个关于中枪脚的主题可能会有数千页之多。^0|0|0|0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|T|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|U|9|@]|A|@]|B|$F|G]]|$2|H|4|I|6|7|8|V|9|@]|A|@]|B|$]]|$2|J|4|K|6|E|8|W|9|@]|A|@]|B|$F|G]]|$2|L|4|M|6|7|8|X|9|@]|A|@]|B|$]]|$2|N|4|O|6|E|8|Y|9|@]|A|@]|B|$F|G]]|$2|P|4|Q|6|7|8|Z|9|@]|A|@]|B|$]]|$2|R|4|S|6|7|8|10|9|@]|A|@]|B|$]]]]

I take the definition of dangerous as "we may ship with that bug and discover only years later when it's to late":

<pre><code>char* c = malloc(...);
.
.
.
free(c); 
.
.
.
c[...] = ...; 
</code></pre>

or

<pre><code>// char* s is an input string
char* c = malloc(strlen(s));
strcpy(c, s);
</code></pre>

But if you write multiplatform (not limited to x86/x64) this is also great:

<pre><code>char* c = ...;
int i = *((int*)c); // &lt;-- alignment fault
</code></pre>

And if your buffer comes from an untrusted source.. basically most code around is dangerous.

But, anyway, in C it's so easy to shoot yourself in the foot, that a topic about shot feet could go around the thousands of pages.

entityMap|blocks|key|an3d6|text|while(a)
{+
+++//+code+-+where+'a'+never+reaches+0+:(+
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript^0^^$0|$]|1|@$2|3|4|5|6|7|8|E|9|@]|A|@]|B|$C|D]]]]

<pre><code>while(a)
{ 
 // code - where 'a' never reaches 0 :( 
}
</code></pre>

entityMap|blocks|key|70ri8|text|切换外壳，无中断。|type|unstyled|depth|inlineStyleRanges|entityRanges|data^0^^$0|$]|1|@$2|3|4|5|6|7|8|C|9|@]|A|@]|B|$]]]]

entityMap|blocks|key|fopm6|text|我记得有两个错误：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|522md|从创建自动变量的函数中返回该自动变量的地址；|6cuol|将字符串复制到未初始化且未分配的字符指针。^0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|G|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|H|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|I|9|@]|A|@]|B|$]]]]

I remember two blunders:

<ol>
<li>returning address of an auto variable from within a function in which it was created;</li>
<li>copying string to an uninitialised and unallocated pointer to char.</li>
</ol>

entityMap|blocks|key|4md88|text|未初始化的数据。|type|unstyled|depth|inlineStyleRanges|entityRanges|data^0^^$0|$]|1|@$2|3|4|5|6|7|8|C|9|@]|A|@]|B|$]]]]

entityMap|blocks|key|50p6g|text|system()，并在参数中包含一些用户提供的字符串。popen()也是如此。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|15s81|使用exec|6hl2d|*|b3tlb|()。|17cpe|当然，这并不是C语言所特有的。^0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|K|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|L|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|M|9|@]|A|@]|B|$]]|$2|G|4|H|6|7|8|N|9|@]|A|@]|B|$]]|$2|I|4|J|6|7|8|O|9|@]|A|@]|B|$]]]]

system() with some user-supplied string in the argument. Same goes for popen().

Use exec*() instead.

Of course, this is not unique to C.

entityMap|blocks|key|4eg83|text|我同意Pat+Mac的观点(尽管他投了反对票)。在C中，你能做的最危险的事情就是简单地把它用在重要的事情上。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|65bg3|例如，一种合理的语言在默认情况下会检查数组边界，如果您试图在数组边界之外徘徊，则会立即停止您的程序(引发异常等)。Ada就是这么做的。Java可以做到这一点。很多其他语言都是这样做的。而不是C。整个黑客行业都是围绕这一语言缺陷而建立的。|d5fvq|这是我个人的一次经历。我与一家公司合作，该公司运行一个飞行模拟器网络，与反射(共享)内存硬件捆绑在一起。他们有一个严重的崩溃漏洞，他们无法追踪，所以我们最好的两个工程师被派到那里去追踪它。他们花了两个月的时间。|177me|事实证明，其中一台机器上的C循环中存在off-by-one错误。一种称职的语言当然会在这里停下来，但是C让它继续，在数组结束后的下一个位置写入一段数据。此内存位置恰好被网络上的另一台计算机使用，该计算机将其传递给|82l0e|第三|4c7di|机器，它使用(垃圾)值作为数组索引。因为这个系统也是用C语言编写的，所以它也不关心它在数组之外的索引方式，也不关心它的程序中的半随机内存位置。|6a2of|因此，由于缺少数组边界检查，一个简单易出错的bug在距离bug来源两个完整跃点的计算机中导致随机崩溃！公司的成本:他们最好的工程师的4个人月的时间，加上其他工程师和支持人员花费的时间，加上所有有问题的模拟器不能正常工作的停机时间。^0|0|0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|O|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|P|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|Q|9|@]|A|@]|B|$]]|$2|G|4|H|6|7|8|R|9|@]|A|@]|B|$]]|$2|I|4|J|6|7|8|S|9|@]|A|@]|B|$]]|$2|K|4|L|6|7|8|T|9|@]|A|@]|B|$]]|$2|M|4|N|6|7|8|U|9|@]|A|@]|B|$]]]]

I'm in agreement with Pat Mac here (despite his downvoting). The most dangerous thing you can do in C is simply to use it for something important.

For example, a sensible language would by default check array bounds and stop your program immediately (raise an exception or something) if you try to wander outside of it. Ada does this. Java does this. Tons of other languages do this. Not C. There are entire hacking industries built around this flaw in the language.

One personal experience with this. I worked with a company that ran a network of flight simulators, tied together with reflective (shared) memory hardware. They were having a nasty crash bug they couldn't track down, so our two best engineers got sent up there to track it down. It took them 2 months.

It turned out that there was an off-by-one error in a C loop on one of the machines. A competent language would have stopped things right there of course, but C let it go ahead and write a piece of data in the next location past the end of the array. This memory location happened to be used by another machine on the network which passed it to a third machine, which used the (garbage) value as an array index. Since this system was also coded in C, it didn't care either that it was indexing way outside of its array, and trashing semi-random memory locations in its program.

So, due to a lack of array bounds checking, a simple easy to make off-by-one bug caused random crashes in a computer two entire hops away from the source of the bug! Cost to the company: 4 man-months of their best engineers' time, plus however much was spent by other engineers and support personnel, plus all the downtime from the simulators in question not working right.

entityMap|blocks|key|7badd|text|#include|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1uom7|我认为C本身就支持字符串(大约在8年前使用Metroworks+codewarrior+)。|unstyled|487ni|我这样做，是为了完成一个大约有15,000行代码的最终项目。我使用这个库来做所有与字符串相关的事情(追加、拆分等)。只是助教不能编译我的任务的任何部分(使用GCC)。|e7p9t|我几乎不知道metroworks已经创建了自己的字符串库。我那门课不及格。^0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|L|9|@]|A|@]|B|$C|D]]|$2|E|4|F|6|G|8|M|9|@]|A|@]|B|$]]|$2|H|4|I|6|G|8|N|9|@]|A|@]|B|$]]|$2|J|4|K|6|G|8|O|9|@]|A|@]|B|$]]]]

<pre><code>#include &lt;string&gt;
</code></pre>

Me thinking C supports string natively (using Metroworks codewarrior, about 8 years ago).

I did this, for a final project of about 15,000 lines of code. I used this library to do everything relating to strings(appending, splitting, etc.) Only to have the TA's not able to compile any bit of my assignment(using GCC.) 

Little did i learn that metroworks had created their own string library. I failed that class.

entityMap|blocks|key|bvm44|text|有两件事浮现在我的脑海中。首先是嵌入式C+(MCU)中的一个函数，我尝试在输入函数时对计时器值进行一些限制。所以我写了|type|unstyled|depth|inlineStyleRanges|entityRanges|data|hjmb|if(55000+<+my_var+<+65000)|code-block|syntax|javascript|apkp5|我的ida是这样检查的：|fccdi|if(+(55000|7qts|if(+(55000|6epjo|get_data(BYTE+**dataptr)
{+
++ubyte*+data+=+malloc(10);
++...+code+...
++*dataptr+=+&data[1];
}

+main()
+{
+++BYTE+*data
+++get_data(&data);
+++free(data);
+}^0|0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|P|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|Q|9|@]|A|@]|B|$F|G]]|$2|H|4|I|6|7|8|R|9|@]|A|@]|B|$]]|$2|J|4|K|6|E|8|S|9|@]|A|@]|B|$F|G]]|$2|L|4|M|6|E|8|T|9|@]|A|@]|B|$F|G]]|$2|N|4|O|6|E|8|U|9|@]|A|@]|B|$F|G]]]]

Two things comes to mind.
Ths first was a function in embedded C (MCU) i tried to have some restrictions on an timer value as a entered a function. so I wrote

<pre><code>if(55000 &lt; my_var &lt; 65000)
</code></pre>

My ida was to check like this:

<pre><code>if( (55000&lt;my_var) &lt; 65000)
</code></pre>

But this is the equivilant or the result

<pre><code>if( (55000&lt;my_var) || (my_var&lt;65000))
</code></pre>

and the result ended up that the if test was always true.

The secound was a pointer mistake. (simplyfied presented here)

<pre><code>get_data(BYTE **dataptr)
{ 
 ubyte* data = malloc(10);
 ... code ...
 *dataptr = &amp;data[1];
}

 main()
 {
 BYTE *data
 get_data(&amp;data);
 free(data);
 }
</code></pre>

Thus resulting in a loss of 1 byte of memory for each time the <code>get_data()</code> function was called

entityMap|blocks|key|5iu2b|text|if+(importantvar+=+importantfunction()+==+VALID_CODE)|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|8io76|这就是我当时的意思：|unstyled|8sk6c|if+((important+var+=+importantfunction())+==+VALID_CODE)|26kfq|当我假设它像后者一样工作时，这导致了许多小时的调试问题。^0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|L|9|@]|A|@]|B|$C|D]]|$2|E|4|F|6|G|8|M|9|@]|A|@]|B|$]]|$2|H|4|I|6|7|8|N|9|@]|A|@]|B|$C|D]]|$2|J|4|K|6|G|8|O|9|@]|A|@]|B|$]]]]

<pre><code>if (importantvar = importantfunction() == VALID_CODE)
</code></pre>

This is when I meant this:

<pre><code>if ((important var = importantfunction()) == VALID_CODE)
</code></pre>

This led to many hours of debugging troubles when I assumed it worked like the latter.

entityMap|blocks|key|amlhn|text|作为一名Lisp程序员，我习惯于缩进右大括号，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2ml8a|(cond
++++((eq+a+foo)(bar+...
++++++++....
++++++++))
++++)|code-block|syntax|javascript|6e4kf|我把这段代码带到了C编程中：|1qmhs|if+(a+==+foo){
++++bar(...);
++++....
++++}|an2rl|然后我开始用C语言做一个很大的项目，另一个程序员不得不在我的代码附近做一些修改。他误读了我的右括号，过早地释放了一些内存。这导致了一个在紧要关头发生的极其微妙的bug。当它被发现的时候，他被责备得很厉害。但你可以说这是我的错。至少可以说，这并不好玩。^0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|N|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|O|9|@]|A|@]|B|$F|G]]|$2|H|4|I|6|7|8|P|9|@]|A|@]|B|$]]|$2|J|4|K|6|E|8|Q|9|@]|A|@]|B|$F|G]]|$2|L|4|M|6|7|8|R|9|@]|A|@]|B|$]]]]

Having been a Lisp programmer, I was used to indenting closing braces, as in:

<pre><code>(cond
 ((eq a foo)(bar ...
 ....
 ))
 )
</code></pre>

and I carried this into C programming:

<pre><code>if (a == foo){
 bar(...);
 ....
 }
</code></pre>

Then I got on a good-size project in C, and another programmer had to make changes in the vicinity of my code. He mis-read my closing brackets, and freed some memory too early. This caused an extremely subtle bug that happened at crunch time. When it was found, he got blamed, badly. But you could say it was my fault. That was not fun, to say the least.

entityMap|blocks|key|bfq8|text|忘记架构约束，愉快地将memcpy()放入微控制器上的内存映射I/O区域。神奇的烟雾从试验台上释放出来。|type|unstyled|depth|inlineStyleRanges|entityRanges|data^0^^$0|$]|1|@$2|3|4|5|6|7|8|C|9|@]|A|@]|B|$]]]]

Forgetting architecture constraints and happily memcpy()ing into the memory mapped I/O area on a microcontroller. The magic smoke was released from the test rig.

entityMap|blocks|key|cnugk|text|我正在处理动态分配的2D数组，我决定释放M列，而不是==+()N行，这对于较小的输入是可以的，其中N==M，但对于大的输入，我只释放分配的50%25。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|d0mdh|耸肩|72p12|活到老学到老。^0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|G|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|H|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|I|9|@]|A|@]|B|$]]]]

I was dealing with dynamically allocated 2D arrays and I instead of free()'ing N rows, I decided to free M columns. This was fine for smaller inputs where N == M but on large inputs, I only free()'d 50% of what I allocated.

shrug

Live and learn.

entityMap|blocks|key|2smc|text|这是一个著名的历史例子(不是我做的)，但是|type|unstyled|depth|inlineStyleRanges|entityRanges|data|eheth|double+d;++++++//+d+gets+populated+with+a+large+number+from+somewhere
short+s+=+d+;++//+overflow|code-block|syntax|javascript|e6cl1|导致|6433m|1egha|爆炸和总损失|1i6e2|的|1gqsg|阿丽亚娜V火箭|8ubcl|..。^0|0|0|0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|S|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|T|9|@]|A|@]|B|$F|G]]|$2|H|4|I|6|7|8|U|9|@]|A|@]|B|$]]|$2|J|4|-4|6|7|8|V|9|@]|A|@]|B|$]]|$2|K|4|L|6|7|8|W|9|@]|A|@]|B|$]]|$2|M|4|N|6|7|8|X|9|@]|A|@]|B|$]]|$2|O|4|P|6|7|8|Y|9|@]|A|@]|B|$]]|$2|Q|4|R|6|7|8|Z|9|@]|A|@]|B|$]]]]

This is a famous historical example (not something I did), but 

<pre><code>double d; // d gets populated with a large number from somewhere
short s = d ; // overflow
</code></pre>

<a href="http://www.ima.umn.edu/~arnold/disasters/ariane.html" rel="nofollow">led to</a> <a href="http://www.youtube.com/watch?v=kYUrqdUyEpI" rel="nofollow">the explosion and total loss</a> of <a href="http://en.wikipedia.org/wiki/Ariane_5_Flight_501" rel="nofollow">an Ariane V rocket</a>.

entityMap|blocks|key|6foum|text|忘了把|type|unstyled|depth|inlineStyleRanges|entityRanges|data|boida|最后。超额|7hhlb|..。错误地键入了一个|2pm3l|这些让我抓狂了几个小时，找出我的代码出了什么问题。^0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|I|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|J|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|K|9|@]|A|@]|B|$]]|$2|G|4|H|6|7|8|L|9|@]|A|@]|B|$]]]]

Forgot to put <code>;</code> at the end. 
 Excess <code>}</code>.
 Mistakenly typed a <code>,</code>

These makes me go nuts for hours finding what stuffs have gone wrong with my codes.

I am an intermediate C programmer. If you have made any coding mistake that you came to know later that it was the most hazardous / harmful to the total application please share that code or description. I want to know this because in future I may come across such situations and I want to have your advice to avoid such mistakes.

What was the most dangerous programming mistake you have made in C?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

文章

问答

视频

学习中心

腾讯云实验室

直播

竞赛

腾讯云代码分析专区

腾讯iOA零信任安全管理系统专区

腾讯云架构师技术同盟交流圈

腾讯云数据库专区

腾讯云顾问专区

腾讯云原生专区

腾讯混元专区

腾讯云TCE专区

腾讯云Lighthouse专区

腾讯云HAI专区

腾讯云Edgeone专区

腾讯云存储专区

腾讯云智能专区

腾讯轻联专区 

腾讯云开发专区

TAPD专区

腾讯轻量云游戏服专区

腾讯云最具价值专家

腾讯云架构师技术同盟

腾讯云创作之星

腾讯云开发者先锋

腾讯云代码助手

云原生构建

TAPD 敏捷项目管理

Cloud Studio

SDK中心

API中心

命令行工具

涵盖代码开发、场景应用、自动测试全流程，助你从零构建专属AI助手

一站式MCP教程库，解锁AI应用新玩法

 我是一个中级C程序员。如果您犯了任何编码错误，后来才知道这是对整个应用程序最危险/最有害的，请分享该代码或说明。我想知道这一点，因为将来我可能会遇到这样的情况，我希望得到您的建议，以避免此类错误。

问你在C中犯过的最危险的编程错误是什么？
EN

Stack Overflow用户

社区

活动

圈层

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问你在C中犯过的最危险的编程错误是什么？EN