Different behaviours for sscanf from STM32Cube and ARM toolchains

[EveRed]

Hi,

I have some code with a call to sscanf from libc.a.

The code is as follow:

uint8_t arg1;
char arg2[7];
char arg3[64];
uint16_t arg4;
uint16_t arg5;
char arg6[8];

sscanf( msg,
"%hhu,\"%[^\"]\",\"%[^\"]\",%hu,%hu,%hhu",
&arg1,
arg2,
arg3,
&arg4,
&arg5,
&arg6);

msg is for instance:

+CIPSTATE:0,"TCP","52.215.18.77",80,55033,0\r\n

I have built it with both STM32CubeIDE embedded libraries, and standard ARM libraries, version 10.3.1.
This code works with STM32CubeIDE libraries, but not with standard ARM toolchains.

Interestingly enough, if I use %d instead of %hhu and let it silently cast, it seems like it works with the default toolchain too.

"%d,\"%[^\"]\",\"%[^\"]\",%hu,%hu,%d"

Is there an explaination for this behaviour?
Are ther implementation differences between libc.a sscanf from the standard ARM toolchain distribution and from the STM32CubeIDE distributed toolchain?

[TDK]

Looks like %hhu is not a standard specifier and implementations treat it differently. Might want to stick with the standards if you want your code to be portable. %u, %d is certainly going to work the same on all implementations.