std：：isinf 在使用 valgrind 运行时程序不起作用

问：

我有这个简单的程序：

test.cc:

#include <limits>
#include <iostream>
#include <cmath>
int main() {
    std::cout << (std::isinf(std::numeric_limits<long double>::infinity()) ? "true" : "false") << std::endl;
}

当我正常运行时，结果符合预期：

g++ -std=c++17 -Wall -Wextra -pedantic -O0 -g3 test.cc && ./a.out:

true

但是，当我使用 valgrind 运行它时，它会打印 .false

g++ -std=c++17 -Wall -Wextra -pedantic -O0 -g3 test.cc && valgrind --leak-check=full -- ./a.out:

==2680== Memcheck, a memory error detector
==2680== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==2680== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info
==2680== Command: ./a.out
==2680==
false
==2680==
==2680== HEAP SUMMARY:
==2680==     in use at exit: 0 bytes in 0 blocks
==2680==   total heap usage: 2 allocs, 2 frees, 73,728 bytes allocated
==2680==
==2680== All heap blocks were freed -- no leaks are possible
==2680==
==2680== For lists of detected and suppressed errors, rerun with: -s
==2680== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

为什么会这样？

（我使用“g++ （Ubuntu 10.3.0-1ubuntu1~20.04） 10.3.0”和“valgrind-3.15.0”。