GNU Make中define、eval与多文件目标的问题求助

Let's tackle your two problems head-on, plus share some optimizations to make your Makefile cleaner, faster, and more reliable.

Problem 1: "Missing Separator" Error #

This error almost always stems from two easy-to-overlook issues:

1.1 Typo in Variable Name #

You defined your directory list as DIRS, but in the foreach loop you wrote $(foreach dir,$(DIR),...) — notice the missing S! Since DIR isn't a defined variable, Make tries to iterate over an empty set, which creates malformed rules and triggers the separator error. Fix it to:

$(foreach dir,$(DIRS),$(eval $(call t4z-recipe-template,$(dir))))

1.2 Recipe Lines Require Tabs #

Make enforces a strict rule: every command line in a recipe must start with a tab character (not spaces). Looking at your template, if the line:

$(call changetree,$(1),$(SRCDIR)) $(DESTDIR) > /dev/null

is indented with spaces instead of a tab, Make will throw the "missing separator" error. Replace those spaces with a single tab to fix this.

Problem 2: Ensuring out4zfiles Expands Correctly in Targets #

Your out4zfiles function should work, but we can refine it to avoid expansion timing issues and boost performance. Right now, you're relying heavily on shell commands, which are slow because each spawns a new subprocess. Let's replace some shell calls with Make's built-in path functions for better speed and reliability.

Optimized Path Handling Functions #

Instead of using shell rev | cut | rev and cut, use Make's native $(subst), $(word), and $(wordlist) functions:

# Replace your existing volume/part/isotope/deptype functions
volume = $(word 3,$(subst /, ,$(1)))
part = $(word 4,$(subst /, ,$(1)))
isotope = $(word 5,$(subst /, ,$(1)))
deptype = $(word 6,$(subst /, ,$(1)))

# Simplify changetree to avoid shell calls
changetree = $(2)/$(wordlist $(words $(subst /, ,$(1)))-3,$(words $(subst /, ,$(1))),$(subst /, ,$(1)))

These built-in functions run directly in Make, no shell overhead, and work consistently across different systems.

Verify Target Expansion #

To confirm your targets are expanding as expected, add a debug rule to print the full list of output files:

debug:
	@echo "All output files: $(ALLT4Z)"

Run make debug — if the output list matches your expectations, your out4zfiles function is working correctly.

Full Fixed & Optimized Core Snippet #

Here's the corrected core section with all fixes applied:

define t4z-recipe-template
$(call out4zfiles,$(1)) : $(wildcard $(call changetree,$(1),$(SRCDIR))/raw-*.root) $(JOBT4Z)
	@# Ensure this line starts with a TAB, not spaces
	$(call changetree,$(1),$(SRCDIR)) $(DESTDIR) > /dev/null
endef

# Fixed foreach loop variable name
$(foreach dir,$(DIRS),$(eval $(call t4z-recipe-template,$(dir))))

Additional Recommendations #

• Minimize shell usage: Each shell call adds overhead. Replace as many as possible with Make's built-in functions for faster execution.
• Use $(info) for debugging: Add lines like $(info Processing directory: $(dir)) inside your foreach loop to debug variable expansion during Make's parsing phase.
• Check for empty inputs: If $(wildcard ...) returns no files, your rules won't trigger. Add a check to warn you if no input files are found, like:

  ifeq ($(wildcard $(call changetree,$(1),$(SRCDIR))/raw-*.root),)
  	$(warning No input files found in $(call changetree,$(1),$(SRCDIR)))
  endif
  

• Keep phony targets: You already have .PHONY : clean all — great, this prevents conflicts with files named clean or all.

内容的提问来源于stack exchange，提问作者gipert