多重定义 - GCC虚假错误 [英] Multiple definitions of - GCC bogus error

问题描述

我有一个头文件 lcd.h用于与此（缩短）：

I have a header file lcd.h with this (shortened):

#pragma once
// ...
const uint8_t LCD_ROW_ADDR[] = {0x00, 0x40, 0x14, 0x54};
// ... other prototypes and macros...

和文件可见的lcd.c ，其中该变量用于：

And a file lcd.c where this variable is used:

#include <stdbool.h>
#include <stdint.h>
// ...

#include "lcd.h"

// ...

/** Set cursor position */
void lcd_xy(const uint8_t x, const uint8_t y)
{
    lcd_set_addr(LCD_ROW_ADDR[y] + (x));
}

我包括 lcd.h用于在的main.c 和可见的lcd.c 正在使用的makefile单独编译。

I include lcd.h in main.c, and lcd.c is compiled separately using makefile.

我得到这个错误：

avr-gcc -std=gnu99 -mmcu=atmega328p -DF_CPU=16000000UL -I. -Ilib/ -funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums -Wall -Wno-main -Wno-strict-prototypes -Wno-comment -g2 -Wextra -Wfatal-errors -ffunction-sections -fdata-sections -Wl,--gc-sections -Wl,--relax -DDEBO_CHANNELS=6 -DDEBO_TICKS=1 -Os main.c lib/debounce.c lib/lcd.c lib/adc.c  --output main.elf
/tmp/ccgfa1iK.o: In function `lcd_xy':
/home/ondra/git/avr-projects/devel/lcdsnake/lib/lcd.c:203: multiple definition of `LCD_ROW_ADDR'
/tmp/cc0iT39O.o:/home/ondra/git/avr-projects/devel/lcdsnake/main.c:424: first defined here
/usr/bin/avr-ld: Disabling relaxation: it will not work with multiple definitions
collect2: error: ld returned 1 exit status
Makefile:87: recipe for target 'main.elf' failed
make: *** [main.elf] Error 1

我已经检查了文件，并多次出现的变量没有其他定义。 第一次这里定义是一个谎言，在的main.c 行包含一个无限循环，code，没有什么与此有关。

I have checked the files multiple times and there is no other definition of the variable. The "first defined here" is a lie, the line in main.c contains an infinite loop code, nothing related to this.

这是怎么回事？

（PS如果我移动变量到可见的lcd.c 文件，它编译好的 - 但我想有它的头文件，所以可以从其他地方访问，太）

(ps. If I move the variable into the lcd.c file, it compiles OK - but I want to have it in the header file, so it can be accessed from elsewhere, too)

推荐答案

LD是正确的。您在感谢两个独立的编译单元定义为标题中的同一个变量。

ld is correct. You have the same variable defined in two separate compilation units thanks to the header.

解决这个问题的办法是把它声明的extern 在头，并只的一个单位的重新声明它没有的extern 预选赛中的.c文件。

The way to fix this is to declare it extern in the header, and have only one of the units redeclare it without the extern qualifier in its .c file.

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