基于Linux内核标头中的功能的条件编译 [英] Conditional compilation based on functionality in Linux kernel headers

问题描述

考虑使用从导出到用户空间的Linux标头中的某些功能的情况，例如 perf_event_open .

Consider the case where I'm using some functionality from the Linux headers exported to user space, such as perf_event_open from <linux/perf_event.h>.

由于成员已添加到perf_event_attr，例如

The functionality offered by this API has changed over time, as members have been added to the perf_event_attr, such as perf_event_attr.cap_user_time.

如果这些新功能在本地可用，我如何编写可以编译和使用这些新功能的源代码，但是如果这些新功能不使用和不使用它们，则如何优雅地回退?

How can I write source that compiles and uses these new functionalities if they are available locally, but falls back gracefully if they aren't and doesn't use them?

尤其是如何在预处理器中检测这些东西是否可用?

In particular, how can I detect in the pre-processor whether this stuff is available?

我以这个perf_event_attr为例，但是我的问题是一个普遍的问题，因为结构成员，新结构，定义和函数一直都在添加.

I've used this perf_event_attr as an example, but my question is a general one because structure members, new structures, definitions and functions are added all the time.

请注意，这里我仅考虑在同一进程上运行该进程的情况:如果要在一个主机上编译而在另一个主机上运行，​​则需要不同的技巧.

Note that here I'm only considering the case where a process is compiled on the same system that it will run on: if you want to compile on one host and run on another you need a different set of tricks.

推荐答案

使用/usr/include/linux/version.h中的宏:

#include <linux/version.h>

int main() {
#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,16)
                                      // ^^^^^^ change for the proper version when `perf_event_attr.cap_user_time` was introduced
   // use old interface
#else
   // use new interface
   // use  perf_event_attr.cap_user_time
#endif
}

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