arm-...-gcc 8.3.1 VS 4.9.3

Dears,

I have been compiling with arm-none-eabi-gcc version 4.9.3 for a while; and everything were just fine with a Cortex-M0  I recently have tried using version 8.3.1 and things are not going as well.

I compiled the exact same code with the released version described earlier.
- ...-gcc 4.9.3: Code complies and runs properly;
- ...-gcc 8.3.1: Code compiles and seems to not execute on target.

I've been looking in the GCC changelogs and I cannot see any change that could explain the behaviour.

The command line is as follows:

arm-none-eabi-(version)
    -g
    -mthumb
    -mcpu:cortex-m0
    -std=c99
    (source files)
    -I (include paths)
    -L (path to linker script)
    -T (linker script)
    -o (target.elf)

Any idea of what could explain the compiler behaviour to change from version 4.9 to 8.3?

Any default option has been changed since 4.9?

I thank you for your help