我正在尝试创建一个宏，该宏将makefile中的define create转换为自动生成的defines列表，defines是外围组件的起始地址。以下是测试代码：
#include <stdio.h>
#include <stdint.h>
/* Created by makefile to specify the core/CPU */
#define CPU_ID 5
/* Autogenerated hardware register descriptors */
#define CPU0_PERIPHERAL_I2C_BASE__ADDR (0x40000)
#define CPU1_PERIPHERAL_I2C_BASE__ADDR (0x56000)
#define CPU2_PERIPHERAL_I2C_BASE__ADDR (0x57000)
#define CPU3_PERIPHERAL_I2C_BASE__ADDR (0x61000)
#define SUBCORE0_PERIPHERAL_I2C_BASE__ADDR (0x67000)
#define SUBCORE1_PERIPHERAL_I2C_BASE__ADDR (0x90000)
#define SUBCORE2_PERIPHERAL_I2C_BASE__ADDR (0xA3000)
#define SUBCORE3_PERIPHERAL_I2C_BASE__ADDR (0xE3000)
#define BASE_ADDR_DEF _PERIPHERAL_I2C_BASE__ADDR
/* defines for translating CPU_ID into autogenerated hardware regs */
#define CPU_ID_0 "CPU0"
#define CPU_ID_1 "CPU1"
#define CPU_ID_2 "CPU2"
#define CPU_ID_3 "CPU3"
#define CPU_ID_4 "SUBCORE0"
#define CPU_ID_5 "SUBCORE1"
#define CPU_ID_6 "SUBCORE2"
#define CPU_ID_7 "SUBCORE3"
#define _JOIN(x,y) x ## y
#define _DEF1(cpu_id) _JOIN(CPU_ID_,cpu_id)
#define _DEF2(cpu_id) _JOIN(_DEF1(cpu_id),BASE_ADDR_DEF)
int main(void)
{
printf("%s\n", _DEF1(CPU_ID)); // <- this prints out "SUBCORE0" which is part of the way there
printf("%X\n", _DEF2(CPU_ID)); // <- This will not compile
return 0;
}
在本例中，输出端的DEF1宏类型将如我所料是“SUBCORE1”。我似乎无法让宏向上转换一个额外的级别，以将“SUBCORE1”与“SUBCORE1”与“SUBCORE1”结合起来，创建“SUBCORE1”和“SUBCORE1”然后打印出十六进制值，该值应为0x90000。在扩展过程中，我是否丢失了另一个级别的宏，而这些宏我看不到或无法得到正确的结果？
编辑：我知道人们在评论文字字符串，我知道这并不是最终目标，但这只是实验中许多迭代步骤中的一个。我只是需要一些例子来说明我想做什么。谢谢。
最佳答案
声明宏不是字符串文本。就像弦一样。将ex."SUBCORE3"更改为SUBCORE3。预处理器无法删除"。
需要使用嵌套宏触发展开。例如#define _JOIN2(x, y) x ## y然后#define _JOIN(x, y) _JOIN2(x, y)
所有以下划线和大字母开头的标识符都由标准保留。声明它们是未定义的行为。
#include <stdio.h>
#include <stdint.h>
/* Created by makefile to specify the core/CPU */
#define CPU_ID 5
/* Autogenerated hardware register descriptors */
#define CPU0_PERIPHERAL_I2C_BASE__ADDR (0x40000)
#define CPU1_PERIPHERAL_I2C_BASE__ADDR (0x56000)
#define CPU2_PERIPHERAL_I2C_BASE__ADDR (0x57000)
#define CPU3_PERIPHERAL_I2C_BASE__ADDR (0x61000)
#define SUBCORE0_PERIPHERAL_I2C_BASE__ADDR (0x67000)
#define SUBCORE1_PERIPHERAL_I2C_BASE__ADDR (0x90000)
#define SUBCORE2_PERIPHERAL_I2C_BASE__ADDR (0xA3000)
#define SUBCORE3_PERIPHERAL_I2C_BASE__ADDR (0xE3000)
#define BASE_ADDR_DEF _PERIPHERAL_I2C_BASE__ADDR
/* defines for translating CPU_ID into autogenerated hardware regs */
#define CPU_ID_0 CPU0
#define CPU_ID_1 CPU1
#define CPU_ID_2 CPU2
#define CPU_ID_3 CPU3
#define CPU_ID_4 SUBCORE0
#define CPU_ID_5 SUBCORE1
#define CPU_ID_6 SUBCORE2
#define CPU_ID_7 SUBCORE3
// usually those are called CONCAT or CONCATX or CONCAT2 or XCONCAT etc.
// so I name them the same here
// XCONCAT is a mnemonic from "eXpand then CONCATenate"
#define CONCAT(x,y) x ## y
#define XCONCAT(x,y) CONCAT(x, y)
#define STRING(x) #x
#define XSTRING(x) STRING(x)
// note that glibc defines __CONCAT __XCONCAT __STRING __XSTRING
// trigger the expansions
#define DEF1(cpu_id) XCONCAT(CPU_ID_, cpu_id)
#define DEF2(cpu_id) XCONCAT(DEF1(cpu_id),BASE_ADDR_DEF)
int main(void)
{
printf("%s\n", XSTRING(DEF1(CPU_ID))); // <- this prints out "SUBCORE0", which is at all not part the way here
printf("%X\n", DEF2(CPU_ID)); // <- This will expand to 0x90000
return 0;
}
关于c - 嵌套预处理器等同于#define，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/57589160/