问题
Consider the following code:
#include <atomic>
#include <iostream>
#include <thread>
std::atomic<int> x, y;
std::atomic<int> r1, r2;
void f()
{
r1 = y.load();
x = r1.load();
}
void g()
{
r2 = x.load();
y = 42;
}
int main()
{
x = 0;
y = 0;
r1 = 0;
r2 = 0;
std::thread t1(f);
std::thread t2(g);
t1.join();
t2.join();
std::cout << r1 << " " << r2 << std::endl;
}
- If I compile this code with
compilers/linux-x86_64-2.10.1/gnu7.1.0/bin/g++ -fsanitize=thread -O3 -std=c++11 main.cpp -o a.out
,TSan
does not provide any warnings and/or threading errors. - However, this code is allowed to produce both
42 0
and0 0
as output.- If
g()
is executed beforef()
starts, thenr1 = y.load()
will have a value of42
- If
g()
is not executed beforef()
starts, thenr1 = y.load()
will have a value of0
.
- If
- Is this something that I should be expecting
TSan
to catch, or are my expectations completely wrong here?- If my expectations are wrong, what can be done (other than code inspection, which can be very difficult for larger code bases) to find bugs such as this?
- In the event that there should be some error thrown, is there some specific option that I am perhaps missing (I'm using all defaults as specified in the document here)?
回答1:
From clang's documentation
ThreadSanitizer is a tool that detects data races
You don't have a data race since all of your variables are atomic, so there is nothing to report.
来源:https://stackoverflow.com/questions/49450136/thread-sanitizer-gives-false-negative-for-function-race