My question is: When I make a project in CubeIDE, if it has the default compiler - GCC, so I needn't to use IAR or Keil.

> My question is: When I make a project in CubeIDE, if it has the default compiler - GCC, so I needn't to use IAR or Keil.

Correct. More precisely, the arm-none-eabi-gcc compiler/toolchain is included and used.

Assuming Windows, the default download area is %USERPROFILE%\STM32Cube\Repository.

Looks like a broken/aborted download. You might want to check/cleanup that folder manually.

USERPROFILE ?

Where is it?

In this website account, or in my CubeIDE?

I have not found it in Cube IDE.

"Assuming Windows, the default download area is %USERPROFILE%\STM32Cube\Repository. "

Do you mean I download "stm32cube_fw_g4" file ?

%USERPROFILE% is your Windows "home" folder, typically C:\Users\<your username>, analogously to $HOME under Linux.

Navigate to the folder %USERPROFILE%\STM32Cube\Repository by any Windows means you know of (explorer, start, cmd, ...) and take a look at the files and folders present in it.

Mine looks like:

...

28.01.2020 10:57   <DIR>         STM32Cube_FW_L5_V1.0.0

28.01.2020 10:57   <DIR>         STM32Cube_FW_L5_V1.1.0

06.01.2020 22:32      183.514.204 stm32cube_fw_l5_v100.zip

28.01.2020 10:56      184.375.604 stm32cube_fw_l5_v110.zip

...

Each downloaded .zip is uncompressed to its own folder by Cube, thus keeping each firmware revision in its own place.

CubeIDE's problem is stated in your screen shot:

CubeIDE hesitates uncompressing into an already existing folder which could overwrite existing data.

Don't know why that folder exists on your machine, it shouldn't.

Maybe from a previous unsuccessful download attempt.

Rename or remove the existing folder and try again.

hth

KnarfB