How to write/read to FLASH on STM32F302 - c

Question

I am making a code using CubeIDE for a STM32F302K8UX and I need a variable to be persistent across resets.
One way I have seen ppl doing it is by making a variable that is saved directly on flash memory (at least this is what I understood of it).
I got it from #Stephan answer on this post:
How to write/read to FLASH on STM32F4, Cortex M4
So I tried following it with a few modifications. On the MEMORY section of STM32F302K8UX_FLASH.ld:
/* Memories definition */
MEMORY
{
RAM (xrw) : ORIGIN = 0x20000000, LENGTH = 16K
FLASH (rx) : ORIGIN = 0x8000000, LENGTH = 63K // subtracted 1kb from original value (64K)
DATA (rx) : ORIGIN = 0x0800FC00, LENGTH = 1K // created new section at the end of previous (0x8000000 + (63 * 1024))
}
Then on the SECTIONS section, I added this at the start:
SECTIONS
{
.user_data (NOLOAD):
{
. = ALIGN(4);
_user_data_start = .; /* create a global symbol at user_data start */
KEEP(*(.user_data))
. = ALIGN(4);
_user_data_end = .; /* create a global symbol at user_data end */
} >DATA
...
Now on my main code I declared the variable as such:
uint8_t persistent_config __attribute__ ((section(".user_data")));
But I get a linker error that I cannot really understand:
14:03:41 **** Incremental Build of configuration Debug for project sonicPlayer ****
make -j12 all
arm-none-eabi-gcc "../Core/Src/main.c" -mcpu=cortex-m4 -std=gnu11 -g3 -DUSE_HAL_DRIVER -DSTM32F302x8 -DDEBUG -c -I../Core/Inc -I../Drivers/STM32F3xx_HAL_Driver/Inc -I../Drivers/STM32F3xx_HAL_Driver/Inc/Legacy -I../Drivers/CMSIS/Device/ST/STM32F3xx/Include -I../Drivers/CMSIS/Include -O0 -ffunction-sections -fdata-sections -Wall -fstack-usage -MMD -MP -MF"Core/Src/main.d" -MT"Core/Src/main.o" --specs=nano.specs -mfpu=fpv4-sp-d16 -mfloat-abi=hard -mthumb -o "Core/Src/main.o"
arm-none-eabi-gcc -o "sonicPlayer.elf" #"objects.list" -mcpu=cortex-m4 -T"C:\Users\werne\OwnCloud\Documents\Arquivos\Drive\Projetos\SonicScrewDriver\sonicPlayer\STM32F302K8UX_FLASH.ld" --specs=nosys.specs -Wl,-Map="sonicPlayer.map" -Wl,--gc-sections -static --specs=nano.specs -mfpu=fpv4-sp-d16 -mfloat-abi=hard -mthumb -Wl,--start-group -lc -lm -Wl,--end-group
c:\st\stm32cubeide_1.4.0\stm32cubeide\plugins\com.st.stm32cube.ide.mcu.externaltools.gnu-tools-for-stm32.7-2018-q2-update.win32_1.4.0.202007081208\tools\arm-none-eabi\bin\ld.exe:C:\Users\werne\OwnCloud\Documents\Arquivos\Drive\Projetos\SonicScrewDriver\sonicPlayer\STM32F302K8UX_FLASH.ld:40: syntax error
collect2.exe: error: ld returned 1 exit status
make: *** [makefile:50: sonicPlayer.elf] Error 1
"make -j12 all" terminated with exit code 2. Build might be incomplete.
14:03:42 Build Failed. 2 errors, 0 warnings. (took 598ms)
Description Resource Path Location Type
make: *** [makefile:50: sonicPlayer.elf] Error 1 sonicPlayer C/C++ Problem
make: *** No rule to make target 'clean'. Stop. Firmware C/C++ Problem
syntax error sonicPlayer line 40, external location: c:\st\stm32cubeide_1.4.0\stm32cubeide\plugins\com.st.stm32cube.ide.mcu.externaltools.gnu-tools-for-stm32.7-2018-q2-update.win32_1.4.0.202007081208\tools\arm-none-eabi\bin\ld.exe:C:\Users\werne\OwnCloud\Documents\Arquivos\Drive\Projetos\SonicScrewDriver\sonicPlayer\STM32F302K8UX_FLASH.ld C/C++ Problem
How do I fix this?
The error description is pretty cryptic to me and I could find anything on google.
If you could explain what is going on here it would be nice too, I'm. not very experienced in this sort of too specific thing.
edit
I can see a syntax error, but no clue where or what.
edit 2: solution:
To fix the error code, I replaced // comments by /* */ as suggested by #KamilCuk However the code was not complete
With a bit more research based on all the other answers, I got this link: https://os.mbed.com/users/olympux/code/eeprom_flash/
So I scrapped all the above, added both .h and .c to my project, replaced #include "mbed.h" for #include "stm32f3xx_hal.h"
then I changed eeprom_flash.c first function
#include "eeprom_flash.h"
FLASH_EraseInitTypeDef eraseInit = {
FLASH_TYPEERASE_PAGES,
EEPROM_START_ADDRESS, // Memory location (beggining of page)
1 // Number of pages to erase
};
uint32_t pageError;
/*
* Must call this first to enable writing
*/
void enableEEPROMWriting() {
HAL_StatusTypeDef status = HAL_FLASH_Unlock();
HAL_FLASHEx_Erase(&eraseInit, &pageError);
}
That was it! to write to flash memory:
enableEEPROMWriting();
writeEEPROMHalfWord(0x0, var);
disableEEPROMWriting();
and to read
uint16_t var = readEEPROMHalfWord(0x0);