Placing variables in absolute memory location (IAR C/C++)

Question

I am working on an STM8S microcontroller with the IAR Compiler.

How can I fix the start location for more then one variable using a pragma or another method?

When I try the below code, the compiler gives this error message:

Error[Lp025]: absolute section .near.bss (main.o #12) ([0x000100-0x000100]) overlaps with absolute section .near.bss (main.o #8) ([0x000100-0x000100])

I searched on IAR tech notes for "Absolute located variable" but I couldn't find any info.

#pragma location = 0x100   /* Start address of absolute location */

extern uint8_t        R0,
                      R1,
                      R2,
                      R3,
extern uint16_t       M1;           
extern uint8_t        M2,    
                      M3;

Maybe [this](http://www.keil.com/support/docs/2829.htm) helps. — Jabberwocky, Sep 22 '17 at 08:15

score 3 · Accepted Answer · answered Sep 22 '17 at 11:19

Use #pragma location = "my_abs" or _Pragma("location=\"my_abs\"") to place the variables you want in the absolute region in the same elf-section. Since #pragma location only applies to the following declaration you may want to create a define that you can prefix when declaring a variable in the absolute block. Note that only the _Pragma("location=\"my_abs\"") syntax is allowed in preprocessor macros.

#pragma section="my_abs"
#define IN_ABS _Pragma("location=\"my_abs\"")

IN_ABS char  R0, R1, R2, R3;
IN_ABS short M1;           
IN_ABS char  M2, M3;

int no_abs;

Then add a line to the linker configuration to put this section at the designated address.

place at address mem:0x100 { rw section my_abs };

Note that you can not mix initialized and uninitialized variables in the same section.

Placing variables in absolute memory location (IAR C/C++)

1 Answers1