pstorage - pstorage_block_identifier_get() and GCC flags -Os -O0 -flto

[Tanasis!]

Hello!

I have encountered an interesting issue:

When I use compiler flags (GCC CFLAGS) -Os or -O0 together with -flto the pstorage function pstorage_block_identifier_get() fails with error NRF_ERROR_INVALID_PARAM.

If I remove the -flto or if I use it together with -O3 it works fine again.

• Any idea why?
• Is it a good idea to use -flto flag? When? (I am confused about this)

I am using SDK9.0.0 and S130 softdevice with nrf51 (16KB RAM / 256 FLASH)

Thanks!

[Hung Bui]

Hi Tanasis: I tried here with a SDK v9.0 example and the flags you mentioned but didn' t have the error. Have you tried to step into the pstorage_block_identifier_get() and check what caused NRF_ERROR_INVALID_PARAM ?

I would suggest to test after a full erase of the chip.

[emdi]

Hi,

-flto is a link time optimization in GCC that enables the linker to perfom optimization as if all function bodies were actually in one single file. If you are very constrained with flash, this option can help reduce the ROM size of you project.

-Os performs a compile time optimization, which favors size.

The SDK is tested using -O3, so strictly speaking -O3 is the safest :) Combining -Os and -flto is a very aggressive optimization and can have side effects.

My guess is that the variable m_app_table in pstorage.c is not properly initialized at startup. It may help to try to manually zero it during initialization.

[Tanasis!]

Hello. @Hung: The error was coming from MODULE_ID_RANGE_CHECK(ID). @emdi: Thanks for the answer. Especially the remark about -Os and -flto. (GCC version is 6.2.2)

[Hung Bui]

@Tanasis: MODULE_ID_RANGE_CHECK(ID) return error invalid param when the id exceeds PSTORAGE_NUM_OF_PAGES. Have you made sure you update the number of pstorage pages according to your usage ?

If you test with unmodified example with the above flags would you have any issue ?

[emdi]

If I remember correctly the macro checks the element of an array which probably gets corrupted when using those optimizations.