请教 __android_log_print，LOG_TAG 问题和原理

[sinkary]

In Android 4.0.3,
I modified the file "system/core/include/cutils/log.h"
I added the code below:

/*
* my log for trace code
*/
#ifndef MYNO
#define MYNO
static long myNo = 0;
#endif
//
#ifndef MYLOG
#define MYLOG(...) \
__android_log_print(ANDROID_LOG_ERROR, LOG_TAG, "***It's My Log!*** No. %ld: ", myNo); \
__android_log_print(ANDROID_LOG_ERROR, NULL, __VA_ARGS__); \
myNo++;
#endif

When i use logcat -s InputReader to see my log, i can only see:
E/InputReader( 308): ***It's My Log!*** No. 0:
E/InputReader( 308): ***It's My Log!*** No. 1:

Must I change the second __android_log_print: NULL to LOG_CAT？
But I want to see the input events show after the number.

I really track the MACRO to know why, but I just can's get the reason.
How can I solve this problem?

[AMinfo]

__android_log_print(ANDROID_LOG_ERROR, LOG_TAG, "***It's My Log!*** No. %ld: " + __VA_ARGS__, myNo);

[sinkary]

[Quote=引用 1 楼 的回复:]

__android_log_print(ANDROID_LOG_ERROR, LOG_TAG, "***It's My Log!*** No. %ld: " + __VA_ARGS__, myNo);
[/Quote]

"..." + __VA_ARGS__
两个字符串不能相加的。
我找到解决办法了，就是仿照__android_log_print重新定义一个MYPRINT：

static int MYPRINT(int prio, const char *tag, const char *fmt, ...) {
va_list ap;

char *my_tag = "***It's My Log!*** No. ";
int len;

char buf[LOG_BUF_SIZE];
len = sprintf(buf, "%s%ld: ", my_tag, myNo++);

va_start(ap, fmt);
vsnprintf(buf+len, LOG_BUF_SIZE-len, fmt, ap);
va_end(ap);

return __android_log_write(prio, tag, buf);
}

[2Tu]

你妹，这是NDK啊。高端 ，求带练级

[dontsaymiss]

这就是一个宏吧

[sinkary]

__VA_ARGS__确实就是一个宏，用来代替MYLOG(...)中省略号所表示的参数列表，它会直接替换成实际的参数。

我是为了写和看自己的log方便，而定义的MYLOG