System Workbench for STM32

HI, I'm a newbie in SW4STM32, and cannot explain why the system cannot find the file gpio.h which is however known in my project. Here is the backgroud:
1- I have produced a very simple file with STM32cubeMX on a STM32L476RG MCU, including 2 GPIOs, PA5 and PC6. I also set the clock to 0.25Mhz, and that's all for this part.
2- I import the project "as is" in SW4STM32
3- I launch the "build project" and I get in the console when compiling gpio.c:

../Src/gpio.c:41:10: fatal error: gpio.h: No such file or directory
#include "gpio.h"
^~~~~~~~
I joined a screenshot describing my eclipse project view where one can see the gpio.h file really present in the tree
I probably missed something somewhere...
Could someone help me ?