这是一个能满足你要求的组装设备。通常不建议使用这样的组装设备;你应该找到一个更好的方法来实现这个目标：

#include <stdio.h>

#define LOG_LEVEL_NORMAL    1
#define LOG_LEVEL_ERROR     2

/*  Define "Message<N>" symbols that will be replaced by the desired prefix
    string.
*/
#define Message1    ""
#define Message2    "MODE_A ERROR "

//  Define a macro to replace a log level with one of the "Message<N>" symbols.
#define MessageFor(log_level)   Message##log_level

#define MODE_A_TRACE_1(log_level, s, p1)    \
    printf(MessageFor(log_level) s "\n", p1)
#define MODE_A_TRACE_2(log_level, s, p1, p2) \
    printf(MessageFor(log_level) s "\n", p1, p2)
#define MODE_A_TRACE_3(log_level, s, p1, p2, p3) \
    printf(MessageFor(log_level) s "\n", p1, p2, p3)

int main(void)
{
    MODE_A_TRACE_1(LOG_LEVEL_NORMAL, "Normal, no prefix, value is %d", 17);
    MODE_A_TRACE_1(LOG_LEVEL_ERROR,  "Error, prefix, value is %d",     42);
}

输出量：

Normal, no prefix, value is 17
MODE_A ERROR Error, prefix, value is 42