BREW AMR 编译错误 L6248E

最新推荐文章于 2023-07-08 18:03:43 发布

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#brew #list #linker #compiler #string #report

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本文探讨了全局变量及指针在位置独立代码中引起的链接错误，并提供了两种解决方案：一是将全局指针替换为全局数组；二是使用局部变量替代全局变量。

主要是由于使用全局变量造成的, 如果要使用全局数组，如 int a[ ] = {1,2,3 };

请在前面加上const , 如下const static int a[ ] = {1,2,3 }; 请勿使用全局指针.

This linker error can occur when trying to build "Position Independent" code. Consider a small example like:

#include <stdio.h>

char *str = "test";

int main(void)
{
    printf ("%s",str);
}

when compiled and linked with:

armcc -c -apcs /ropi pi.c
armlink -ropi pi.o

the linker will report a message of the form:

Error: L6248E: pi.o(.data) in ABSOLUTE region 'ER_RW' cannot have address/offset type
relocation to .constdata in PI region 'ER_RO'.

For the code above, the compiler generates a global pointer "str" to the char string "test". The global pointer "str" will need to be initialized to the address of the char string "test" in the .constdata section. However, absolute addresses cannot be used in a PI system, so the link step fails, because of the ABS32 relocations to (position independent) .constdata.

To resolve this, you must re-write the code to avoid the explicit pointer. Two possible ways are shown below:

1) Use a global array instead of a global pointer:

#include <stdio.h>

const char str[] = "test";

int main(void)
{
    printf ("%s",str);
}

2) Use a local pointer instead of a global pointer:

#include <stdio.h>

int main(void)
{
    char *str = "test";
    printf ("%s",str);
}

Please note that if you are using a list with multiple elements, such as:

char * list[] = {"zero", "one", "two"};

You will get a separate link error for each element in the array. In this case, the recommended solution is:

char list[3][5] = {"zero", "one", "two"};

with the print instruction being (for example):

printf("%s", list[1]);

Note that you will need to declare a two dimensional array for the list, with the first dimension as the number of elements in the array, and the second dimension as the maximum size for an element in the array.