From c7c389845d7a357c24e1ed46195efafa2817104d Mon Sep 17 00:00:00 2001
From: ctkiku <kim.kuparinen@tuni.fi>
Date: Mon, 28 Sep 2026 17:25:01 +0300
Subject: [PATCH] make: immediately expand deferred vars, v2

Previous approach apparently caused some externally-defined variables to
become overwritten, and modifications made in 72eca88 effectively
reverted back to the old behaviour of spawning 28k shells for each
`make` invocation. Try to cut that number down to 41 again by explicitly
checking if the variables have been externally defined.

Signed-off-by: ctkiku <kim.kuparinen@tuni.fi>
---
 flow/scripts/variables.mk | 35 ++++++++++++++++++++++-------------
 1 file changed, 22 insertions(+), 13 deletions(-)

diff --git a/flow/scripts/variables.mk b/flow/scripts/variables.mk
index 6567737158..3fa9694a18 100644
--- a/flow/scripts/variables.mk
+++ b/flow/scripts/variables.mk
@@ -80,7 +80,9 @@ export NUM_CORES
 # that does not exist in a Bazel sandbox). A bare `export` preserves the
 # original origin (environment when bazel-orfs supplies it, file when the
 # local default fills in), so the value survives UNSET_VARS.
-PYTHON_EXE ?= $(shell command -v python3)
+ifeq ($(origin PYTHON_EXE), undefined)
+  PYTHON_EXE := $(shell command -v python3)
+endif
 export PYTHON_EXE
 
 export RUN_CMD = $(PYTHON_EXE) $(FLOW_HOME)/scripts/run_command.py
@@ -91,15 +93,20 @@ export RUN_CMD = $(PYTHON_EXE) $(FLOW_HOME)/scripts/run_command.py
 #       2 either
 #          2.1 if in Nix shell: openroad, yosys from the environment
 #          2.2 ORFS compiled tools: openroad, yosys
-ifneq (${IN_NIX_SHELL},)
-  OPENROAD_EXE ?= $(shell command -v openroad)
-else
-  OPENROAD_EXE ?= $(abspath $(FLOW_HOME)/../tools/install/OpenROAD/bin/openroad)
+ifeq ($(origin OPENROAD_EXE), undefined)
+  ifneq (${IN_NIX_SHELL},)
+    OPENROAD_EXE := $(shell command -v openroad)
+  else
+    OPENROAD_EXE := $(abspath $(FLOW_HOME)/../tools/install/OpenROAD/bin/openroad)
+  endif
 endif
-ifneq (${IN_NIX_SHELL},)
-  OPENSTA_EXE ?= $(shell command -v sta)
-else
-  OPENSTA_EXE ?= $(abspath $(FLOW_HOME)/../tools/install/OpenROAD/bin/sta)
+
+ifeq ($(origin OPENSTA_EXE), undefined)
+  ifneq (${IN_NIX_SHELL},)
+    OPENSTA_EXE := $(shell command -v sta)
+  else
+    OPENSTA_EXE := $(abspath $(FLOW_HOME)/../tools/install/OpenROAD/bin/sta)
+  endif
 endif
 
 # See dragons comment near PYTHON_EXE: bare `export`, not `export VAR := $(VAR)`.
@@ -114,10 +121,12 @@ export OPENROAD_NO_EXIT_CMD = $(OPENROAD_EXE) $(OPENROAD_ARGS)
 export OPENROAD_GUI_CMD = $(OPENROAD_EXE) -gui -threads $(NUM_CORES) $(OR_ARGS)
 export OPENROAD_WEB_CMD = $(OPENROAD_EXE) -web -threads $(NUM_CORES) $(OR_ARGS)
 
-ifneq (${IN_NIX_SHELL},)
-  YOSYS_EXE ?= $(shell command -v yosys)
-else
-  YOSYS_EXE ?= $(abspath $(FLOW_HOME)/../tools/install/yosys/bin/yosys)
+ifeq ($(origin YOSYS_EXE), undefined)
+  ifneq (${IN_NIX_SHELL},)
+    YOSYS_EXE := $(shell command -v yosys)
+  else
+    YOSYS_EXE := $(abspath $(FLOW_HOME)/../tools/install/yosys/bin/yosys)
+  endif
 endif
 
 # See dragons comment near PYTHON_EXE: bare `export`, not `export VAR := $(VAR)`.