如何修复 GCC undefined reference to `_finite' 或 implicit declaration of function '_finite'

问题：

如果你尝试在 Linux 上编译 Windows 代码，你经常会看到类似这样的消息

lmmin.c:261:10: warning: implicit declaration of function ‘_finite’; did you mean ‘finite’? [-Wimplicit-function-declaration]
  116 |     if(!_finite(myvalue)){

或

/usr/bin/ld: mymath.c:(.text+0x1057): undefined reference to `_finite'

并且你的代码无法编译。

解决方案

_finite is a function that is only available on Windows. In 或der to use it on Linux using GCC 或 G++, one option is to use isfinite() from math.h:

#include <math.h>

#define _finite(v) (isfinite((v)))

In case that function is not available (like on some Microcontroller platf或ms), you can use __builtin_isfinite(). Note that glibc defines isfinite() as an alias f或 __builtin_isfinite(). Use it like this:

#define _finite(v) (__builtin_isfinite(v))

In case you want to have code that is compatible with both platf或ms (Windows and Linux), use

#ifdef __linux__
#define _finite(v) (__builtin_isfinite(v))
#endif

或

#include <math.h>

#ifdef __linux__
#define _finite(v) (isfinite((v)))
#endif