如何抑制来自 UBsan 的一些无符号整数溢出错误? [英] How to suppress some unsigned-integer-overflow errors from UBsan?

问题描述

我的大部分 -fsanitize=unsigned-integer-overflow 错误都是错误，但有时我会按预期明确使用它，这会导致 UBSan 产生误报.

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.

有没有办法关闭特定表达式的 UBSan 无符号整数溢出检查?

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

编辑以回应 Shafik 的评论，这是一个例子:

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

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

大多数时候这是一个错误，有时不是.使用 UBSan 可以发现每次发生的情况，修复错误，但我还没有找到一种方法来消除误报.

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:要启用检查，需要通过 -fsanitize=integer(启用所有整数检查)或 fsanitize=unsigned-integer-overflow.从下面的评论来看，该检查似乎仅在 clang 中可用，而在 GCC 中尚不可用.

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.

推荐答案

如果你想将操作包装在一个函数中，你可以像这样使用 __attribute__((no_sanitize("integer")))(现场观看):

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 ;
}

我是通过错误报告/功能请求发现的对 UbSAN 的抑制支持.

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

clang 关于属性的文档 并没有指出任何应用它的方法，除了应用于功能:

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

在函数声明中使用 no_sanitize 属性来指定不应将特定检测或检测集应用于该函数.该属性采用字符串文字列表，其含义与 -fno-sanitize= 标志接受的值相同.例如，attribute((no_sanitize("address", "thread"))) 指定不应将 AddressSanitizer 和 ThreadSanitizer 应用于函数.

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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