About environment variable D

[cielavenir]

I have found that D=name=value make can be used to set additional define. It is used in make.inc DEFINES += $(addprefix -D , $D) and Makefile.am AM_CFLAGS = ${my_CFLAGS} ${INCLUDE} $(src_include) ${D} (oh actually Makefile.am syntax is inconsistent with make.inc). Could you tell me the usecase?
I'm sure python-isal's build system has no usecase so I'm suggesting removing it in pycompression/python-isal#92, but I'm interested in isa-l itself.

In our case, I found that export D=/path/to/detection causes build error.

/cc @rhpvorderman

[gbtucker]

@cielavenir, It is a shortcut for adding additional defines without changing other flags. We can change it but some internal and included tools rely on it such as the test scripts in /tools/test_*.sh. Perhaps we can just override the environment variable by presetting to null and then only the command line can override. Please see linked PR.