makefile: syntax error near unexpected token `,' - makefile

Question

I did not succeed to fix the issue while executing the following code:
%.o: %.c
if [ $(notdir $<) = file1.c ]; then \
echo " >> $(notdir $<) is excluded"; \
else\
ifneq ($(FLAG1),)
$(run_function1)
endif
ifneq ($(FLAG2),)
$(run_function2)
endif
fi
The issue is the following:
if [ file2.c = file1.c ]; then \
echo " >> file2.c is excluded"; \
else\
ifneq (,)
/bin/sh: -c: line 4: syntax error near unexpected token `,'
/bin/sh: -c: line 4: ` ifeq (,)'
Any idea?

Answer 1

You are mixing Shell and Makefile syntax in the recipe. Keep in mind the recipe is passed to the shell pretty much un-modified except for $() variable expansions (i.e.: the ifneq and similar Make conditionals are not expanded if they are indented). See especially the first paragraph and 4th bullet of the documentation here: https://www.gnu.org/software/make/manual/html_node/Recipe-Syntax.html
What you meant to say is something like this, but this does not work due to the \ line continuation subsuming the subsequent ifndef/endif (ideas anyone?):
%.o: %.c
if [ $(notdir $<) = file1.c ]; then \
echo " >> $(notdir $<) is excluded"; \
else \
ifneq ($(FLAG1),)
$(run_function1); \
endif
ifneq ($(FLAG2),)
$(run_function2); \
endif
fi
The conditional Make function should still work:
%.o: %.c
if [ $(notdir $<) = file1.c ]; then \
echo " >> $(notdir $<) is excluded"; \
else \
$(if $(FLAG1),,$(run_function1);) \
$(if $(FLAG2),,$(run_function2);) \
fi
Or possibly using shell conditionals is clearer:
%.o: %.c
if [ $(notdir $<) = file1.c ]; then \
echo " >> $(notdir $<) is excluded"; \
else \
if [ -n $(FLAG1) ] \
$(run_function1); \
fi \
if [ -n $(FLAG2) ] \
$(run_function2); \
fi \
fi