According to the gmake 4.3 release docs:
* WARNING: Backward-incompatibility!
Number signs (#) appearing inside a macro reference or function invocation
no longer introduce comments and should not be escaped with backslashes:
thus a call such as:
foo := $(shell echo '#')
is legal. Previously the number sign needed to be escaped, for example:
foo := $(shell echo '\#')
Now this latter will resolve to "\#". If you want to write makefiles
portable to both versions, assign the number sign to a variable:
H := \#
foo := $(shell echo '$H')
This was claimed to be fixed in 3.81, but wasn't, for some reason.
To detect this change search for 'nocomment' in the .FEATURES variable.
* WARNING: Backward-incompatibility!
Previously appending using '+=' to an empty variable would result in a value
starting with a space. Now the initial space is only added if the variable
already contains some value. Similarly, appending an empty string does not
add a trailing space.
Not sure if any of the above are a factor
