Undefined Behavior Sanitizer：如何抑制一些无符号整数溢出错误？ [英] Undefined Behavior Sanitizer: How to suppress some unsigned-integer-overflow errors?

问题描述

我的 -fsanitize = unsigned-integer-overflow 错误大多是错误，但有时我明确地使用它的预期，这导致UBSan产生假阳性。 p>

有没有办法可以为特定表达式关闭UBSan无符号整数溢出检查？

到Shafik的注释，这里是一个例子：

  unsigned a = 0; 
 unsigned b = a  -  1; //错误：无符号整数溢出
  

大多数时间是一个错误，有时不是。对于UBSan，可以找到每一次发生的问题，修复错误，但是我没有找到一种方法来消除假阳性。

编辑2：启用检查需要传递 -fsanitize = integer （以启用所有整数检查）或 fsanitize = unsigned-integer-overflow 。

解决方案

如果你想包装在一个函数中的操作你可以使用 __ attribute __（（no_sanitize（integer）））这样（ 查看活动

）：

  __attribute __（（no_sanitize（integer）））
 unsigned calc（unsigned a）
 {
 return a  -  1; 
} 
  

我通过错误报告/功能请求找到了对UbSAN的抑制支持。

a href =http://clang.llvm.org/docs/AttributeReference.html =nofollow>关于属性的文档不表示任何方式应用此功能，除非功能：

在函数声明中使用no_sanitize属性来指定特定的检测或检测集合不应该应用于该函数。该属性采用字符串字面值列表，其与-fno-sanitize =标志接受的值具有相同的含义。例如， attribute （（no_sanitize（address，thread）））指定AddressSanitizer和ThreadSanitizer不应用于该函数。

Most of my -fsanitize=unsigned-integer-overflow errors are bugs, but sometimes I explicitly use it as intended, which results in UBSan producing false positives.

Is there a way to turn UBSan unsigned-integer-overflow check off for a particular expression?

EDIT in response to Shafik comment, here is an example:

unsigned a = 0;
unsigned b = a - 1; // error: unsigned integer overflow

Most of the time that is a bug, sometimes it isn't. With UBSan one can find every time that happens, fix the bugs, but I haven't found a way to silence the false positives.

EDIT 2: to enable the check one needs to pass either -fsanitize=integer (to enable all integer checks) or fsanitize=unsigned-integer-overflow. From the comments below it seems that the check is only available in clang and not in GCC yet.

解决方案

If you want to wrap the operation in a function you can use __attribute__((no_sanitize("integer"))) like so (see it live):

__attribute__((no_sanitize("integer")))
unsigned calc( unsigned a )
{
    return a - 1 ;
}

I found this via a bug report/feature request Suppression support for UbSAN.

The clang documentation on attributes does not indicate any way to apply this except to a function:

Use the no_sanitize attribute on a function declaration to specify that a particular instrumentation or set of instrumentations should not be applied to that function. The attribute takes a list of string literals, which have the same meaning as values accepted by the -fno-sanitize= flag. For example, attribute((no_sanitize("address", "thread"))) specifies that AddressSanitizer and ThreadSanitizer should not be applied to the function.

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