Hi,
after one of my rarely touched projects wasn't working any longer properly (although it did compile without errors), I was able to reproduce the issue even by using the sample project from the STM32F4xx package:
- Create a new solution/project with STM32F4xx package "C/C++ executable for STM32F4xx"
- Choose target STM32F405RG
- Settings: Compiler: Either GCC or SEGGER, Linker: SEGGER
- Change the main.c to this to verify the rand() function:
EDIT: With SEGGER compiler the problem doesn't show up like this, because the memory regions are setup differently, but the memory address used by rand() is still wrong by 4 bytes.
//-----------------------
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void) {
int i, r;
static char some_data[10000];
for (i = 0; i < 100; i++) {
r = rand();
memset(some_data, 0, 10000);
printf("Hello World %d!\n", r);
}
do {
i++;
} while (1);
}
//-----------------------
The program should output random numbers, but the actual output is:
Hello World 0!
Hello World 0!
...
After some investigation I noticed the created memory map in the .map file doesn't match the what the created code is actually doing:
In the .map file I have:
10000000-10000003 __SEGGER_RTL_rand_next 4 4 Init RW intops.o (libc_v7em_fpv4_sp_d16_hard_t_le_eabi_balanced.a)
10000004-10002713 some_data.0 10 000 4 Zero ZI main.o
That means the rand() function is using 0x10000000-0x10000003 for some purpose, the array some_data is at location 0x10000004-0x10002713.
In the created code, the rand() function is infact using memory 0x10000004-0x10000007 erroneously which causes a collision with the memory of the array. Due to the fact that the code is zeroing the array, the output of rand() is always 0.
So for (to me) unknown reason, there is a memory offset of 4 between the memory map and the memory used by the rand() function in the C lib.
Please find the screenshot I did during debugging attached.
The rand() function accesses [r0, r1] (indirect), which is 0x0ffffffc + 0x00000008 = 0x10000004 (!!!) in this case, and it is wrong (should be 0x10000000).
Maybe this is related to a wrong offset returned by the __aebi_read_tp function, but how could it be fixed? Is there anything wrong on my side / settings?
I checked this with Embedded Studio 6.40 as well as with 7.10a.
Regards
Markus
after one of my rarely touched projects wasn't working any longer properly (although it did compile without errors), I was able to reproduce the issue even by using the sample project from the STM32F4xx package:
- Create a new solution/project with STM32F4xx package "C/C++ executable for STM32F4xx"
- Choose target STM32F405RG
- Settings: Compiler: Either GCC or SEGGER, Linker: SEGGER
- Change the main.c to this to verify the rand() function:
EDIT: With SEGGER compiler the problem doesn't show up like this, because the memory regions are setup differently, but the memory address used by rand() is still wrong by 4 bytes.
//-----------------------
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void) {
int i, r;
static char some_data[10000];
for (i = 0; i < 100; i++) {
r = rand();
memset(some_data, 0, 10000);
printf("Hello World %d!\n", r);
}
do {
i++;
} while (1);
}
//-----------------------
The program should output random numbers, but the actual output is:
Hello World 0!
Hello World 0!
...
After some investigation I noticed the created memory map in the .map file doesn't match the what the created code is actually doing:
In the .map file I have:
10000000-10000003 __SEGGER_RTL_rand_next 4 4 Init RW intops.o (libc_v7em_fpv4_sp_d16_hard_t_le_eabi_balanced.a)
10000004-10002713 some_data.0 10 000 4 Zero ZI main.o
That means the rand() function is using 0x10000000-0x10000003 for some purpose, the array some_data is at location 0x10000004-0x10002713.
In the created code, the rand() function is infact using memory 0x10000004-0x10000007 erroneously which causes a collision with the memory of the array. Due to the fact that the code is zeroing the array, the output of rand() is always 0.
So for (to me) unknown reason, there is a memory offset of 4 between the memory map and the memory used by the rand() function in the C lib.
Please find the screenshot I did during debugging attached.
The rand() function accesses [r0, r1] (indirect), which is 0x0ffffffc + 0x00000008 = 0x10000004 (!!!) in this case, and it is wrong (should be 0x10000000).
Maybe this is related to a wrong offset returned by the __aebi_read_tp function, but how could it be fixed? Is there anything wrong on my side / settings?
I checked this with Embedded Studio 6.40 as well as with 7.10a.
Regards
Markus
