-Wvla compiler warnings

[zfields]

Running this Arduino CLI command from the folder of a sketch that #includes the "Arduino_DebugUtils" library:

arduino-cli compile --verbose --warnings=all --build-property "build.extra_flags=-Wno-unused-variable -Wno-implicit-fallthrough -Wno-psabi -Wno-deprecated-copy -Wno-missing-field-initializers -Wno-delete-non-virtual-dtor -Wno-sign-compare -Og -g" --fqbn arduino:mbed_opta:opta

results in this compiler warning:

~/Development/Arduino/libraries/Arduino_DebugUtils/src/Arduino_DebugUtils.cpp: In member function 'void Arduino_DebugUtils::vPrint(const char*, va_list)':
~/Development/Arduino/libraries/Arduino_DebugUtils/src/Arduino_DebugUtils.cpp:139:28: warning: variable length array 'msg_buf' is used [-Wvla]
   char msg_buf[msg_buf_size];
                            ^

[aentinger]

Variable length arrays are not perfect, but a better solution than dynamic memory allocation on the heap. If you have a sensible design recommendation to eliminate a variable length array in this library (w/o resorting to heap) I'll be happy to review it.

[zfields]

@aentinger I have always used alloca() (auto-freed, stack allocation) in the past, but I'm not sure if that's available to all the embedded platforms you support.

https://www.man7.org/linux/man-pages/man3/alloca.3.html

[zfields]

If alloca() is not an option, then it would be good to document -Wvla as a required compiler flag.