@User: Sorry for being AWOL through most of that thread. I used to have the open_pdks install just the way I liked it until Tim Ansell made me change it to be more compliant with typical Linux packages. At any rate, the value of $SHARED_PDKS_PATH is used by the open_pdks Makefile and is the only way to do an end-run around the Makefile inserting /share/ into the path everywhere. I documented that somewhere, but I need to figure out exactly where.

Whenever I use that variable I get this error over and over:

# Install OSU T18 ls digital standard cells.
set -f ; ../common/foundry_install.py -std_format -source  -target /software/PDKs/open_pdks/sky130/sky130A \
        -techlef sky130_osu_sc_18T.tlef rename=sky130_osc_sc_18t_ls.tlef \
        -spice 18T_ls/cdl/*.spice compile-only exclude=*.*.spice \
        -lef 18T_ls/lef/*.lef \
        -lib 18T_ls/lib/*.lib \
        -gds 18T_ls/gds/*.gds compile-only \
                options=custom/scripts/gds_import_setup.tcl \
        -library digital sky130_osu_sc_18t_ls 2>&1 | tee -a sky130A_make.log
Traceback (most recent call last):
  File "../common/foundry_install.py", line 430, in <module>
    sourcedir = option[1]

That probably means that I broke something, as I have not tested the non-standard install location for some number of commits. I'll check that and confirm.

Actually, this could be something on my end. I think my version was pretty stale as well.

Okay. I thought that for Makefiles, you only need to pass the variable to the "make" command, but if the "?=" works in the Makefile, then that's better.

That should only make the assignment if it isn't already defined

Since makefile overrides have always been a little confusing to me, I made the following test

Makefile

TEST_VAR = default1
TEST_ENV_VAR ?= default2

test:
	echo $(TEST_VAR) > /dev/null
	echo $(TEST_ENV_VAR) > /dev/null

and ran the following script

echo "default"
unset TEST_VAR
unset TEST_ENV_VAR
make test

echo " "
echo "command line override"
make TEST_VAR=commandLine1 TEST_ENV_VAR=commandLine2 test

echo " "
echo "environment override"
export TEST_VAR=override1
export TEST_ENV_VAR=override2
make test

echo " "
echo "environment/command line override"
make TEST_VAR=commandLine1 TEST_ENV_VAR=commandLine2 test

and got the following results

default
echo default1 > /dev/null
echo default2 > /dev/null
 
command line override
echo commandLine1 > /dev/null
echo commandLine2 > /dev/null
 
environment override
echo default1 > /dev/null
echo override2 > /dev/null
 
environment/command line override
echo commandLine1 > /dev/null
echo commandLine2 > /dev/null

So environment variables override

?=

assignments but not

=

assignments, while command line assignments override both

?=

and

=

assignments and ignore environment variables. FWIW.

Interesting. I was running like this: TEST_VAR=commandLine1 make test which must be an environment variable as well.