是否存在通过C库而不是通过命名空间std使用符号的GCC警告? [英] Is there a GCC warning for using symbols from the C library not through namespace std?

问题描述

考虑以下(笨拙的)C ++代码:

Consider the following (buggy) C++ code:

#include <cmath>
#include <cstdlib>

#include <iostream>

int main() {
    if (abs(-0.75) != 0.75) {
        std::cout << "Math is broken!\n";
        return 1;
    } else {
        return 0;
    }
}

此代码有错误，因为它调用 abs (意思是 :: abs )而不是 std :: abs .根据实现的不同， :: abs 可能不存在，或者它可能是C abs ，或者它可能是一个过载集，其中包括 double ，例如 std :: abs 是.

This code is buggy because it calls abs (meaning ::abs) instead of std::abs. Depending on the implementation, ::abs might not exist, or it might be the C abs, or it might be an overload set including a version for double, like std::abs is.

至少在我的环境中，使用Linux上的Clang时，事实证明它是第二个选项:C abs .即使未显式启用任何警告，这也会引发两个警告:

With Clang on Linux, at least in my environment, it turns out to be the second option: C abs. This provokes two warnings, even without explicitly enabling any:

<source>:7:9: warning: using integer absolute value function 'abs' when argument is of floating point type [-Wabsolute-value]
    if (abs(-0.75) != 0.75) {
        ^
<source>:7:9: note: use function 'std::abs' instead
    if (abs(-0.75) != 0.75) {
        ^~~
        std::abs
<source>:7:13: warning: implicit conversion from 'double' to 'int' changes value from -0.75 to 0 [-Wliteral-conversion]
    if (abs(-0.75) != 0.75) {
        ~~~ ^~~~~

在GCC上，我在不同的环境中得到了不同的结果，但是我还没有弄清楚该环境的哪些细节是相关的.不过，更常见的选择是它也调用C abs 函数.但是，即使使用 -Wall -Wextra -pedantic ，它也不会发出警告.我可以通过 -Wfloat-conversion 强制发出警告，但这会给我的其余代码库带来太多误报(也许我应该解决，但这是另一个问题):

On GCC, I get different results in different environments and I haven’t yet figured out what details of the environment are relevant. The more common option, though, is also that it calls the C abs function. However, even with -Wall -Wextra -pedantic, it gives no warnings. I can force a warning with -Wfloat-conversion, but that gives too many false positives on the rest of my codebase (which perhaps I should fix, but that’s a different issue):

<source>: In function 'int main()':
<source>:7:18: warning: conversion to 'int' alters 'double' constant value [-Wfloat-conversion]
     if (abs(-0.75) != 0.75) {
                  ^

当命名空间 std 中的版本超载时，是否有办法通过全局命名空间使用库函数来发出警告?

Is there a way to get a warning whenever I use a library function through the global namespace, when the version in namespace std is an overload?

推荐答案

这是一个解决方案.我对此不满意，但它可能对您有用:

Here's a solution. I'm not happy with it, but it might work for you:

namespace DontUseGlobalNameSpace {
// put all std functions here you want to catch
int abs(int x);
}
using namespace DontUseGlobalNameSpace;

现在，如果您不加限定地使用 abs()，则会出现符号不明确"错误.

Now, if you use abs() without qualification, you'll get a "symbol is ambiguous" error.

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