mdk制作外部flash下载算法， 编译错误 L6248E

问题

使用MDK提供的模板制作外部flash下载算法，加入自己的代码后，编译时，在链接时报错：

linking…
Error: L6248E: sfud.o(.data) in PI region ‘PrgData’ cannot have address type relocation to .conststring in PI region ‘PrgCode’.

解决方法

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

• 2. Use a local pointer instead of a global pointer:

#include 
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.