-O3 triggers compiler error #3734

Hello,

compiling my source code, I encountered the following compiler error:

"no source": Error: #3734: __packed qualifier dropped when passing argument to unprototyped function

The MCU architecture is Cortex-M0.

The error is triggered when I change the compiler optimisation from o2 to o3. All the routines that the compiler labelled as unprototyped have the prototype in a separate header file.

The prototypes are always included and never disabled by specific #ifs.., aside from the main #ifndef _HEADER_ - #define _HEADER_ - #endif, of the header file.

It's been a while that I am stuck with this issue, no solution already identified. I tried to find information about this error but without success. Could you help me in understanding the source of the problem and how to work on a possible workaround?

Thanks in advance for all your support.

Regards,
Alessandro