如何最好地消除有关未使用变量的警告?

2021-12-18 00:00:00 gcc warnings c++ gcc-warning

我有一个跨平台应用程序，在我的一些函数中，并非所有传递给函数的值都被利用.因此我收到 GCC 的警告，告诉我有未使用的变量.

I have a cross platform application and in a few of my functions not all the values passed to functions are utilised. Hence I get a warning from GCC telling me that there are unused variables.

围绕警告编码的最佳方式是什么?

What would be the best way of coding around the warning?

函数周围的#ifdef?

An #ifdef around the function? 

#ifdef _MSC_VER
void ProcessOps::sendToExternalApp(QString sAppName, QString sImagePath, qreal qrLeft, qreal qrTop, qreal qrWidth, qreal qrHeight)
#else
void ProcessOps::sendToExternalApp(QString sAppName, QString sImagePath, qreal /*qrLeft*/, qreal /*qrTop*/, qreal /*qrWidth*/, qreal /*qrHeight*/)
#endif
{

这太难看了，但似乎是编译器喜欢的方式.

This is so ugly but seems like the way the compiler would prefer.

或者我是否在函数末尾为变量赋值为零?(我讨厌它，因为它改变了程序流程中的某些内容以消除编译器警告).

Or do I assign zero to the variable at the end of the function? (which I hate because it's altering something in the program flow to silence a compiler warning).

有正确的方法吗?

推荐答案

您可以将它放在 "(void)var;" 表达式(什么都不做)中，以便编译器看到它被使用.这在编译器之间是可移植的.

You can put it in "(void)var;" expression (does nothing) so that a compiler sees it is used. This is portable between compilers.

例如

void foo(int param1, int param2)
{
    (void)param2;
    bar(param1);
}

或者，

#define UNUSED(expr) do { (void)(expr); } while (0)
...

void foo(int param1, int param2)
{
    UNUSED(param2);
    bar(param1);
}

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