variable expansion in subshell in makefile fails - function

Question

I have a makefile function inside a makefile (myfunction.mk):
.ONESHELL:
define call_script
set +x
mkdir -p $$(dirname $(2))
if [ ! -f $(2) ]; then
echo "" > $(2)
fi
REDIRECT='| tee -a'
echo '>> $(1)'
($(1) ???????? $(2))
RET_CODE=$$?
echo "exit_code is: $$RET_CODE"
if [ ! $$RET_CODE = 0 ]; then
echo "$(3) terminated with error $$RET_CODE"
exit $$RET_CODE
else
if [ ! -z "$(strip $(3))" ]; then
echo "$(3) done"
fi
fi
endef
this function call a script and append result to a log (which is created with its folder if non existing), the result of the script is append only if the makefile variable given as the 4th ($(4)) argument is equal to 'yes'.
you call it like this:
include myfunction.mk
OUTPUT_ENABLED ?= yes
target:
$(call call_script, echo "test", reports/mylog.log, "doing test", OUTPUT_ENABLED)
This works for the most part:
if i replace '????????' by '| tee -a', it works.
if i replace '????????' by $(REDIRECT), it fails.
if i replace '????????' by $$REDIRECT, it fails.
why?
note: running it from a shell /bin/sh: symbolic link to dash
note: of course i want to add a ifeq that allows me to check for $(4) and replace | tee -a by &>>

Answer 1

I'll assume that you use call in a recipe, not flat in your Makefile. There are few problems with your shell script. First, if you try the following on the command line:
mkdir -p reports
REDIRECT='| tee -a'
echo '>> echo "test"'
(echo "test" $REDIRECT reports/mylog.log)
you'll see that echo considers:
"test" $REDIRECT reports/mylog.log
as its arguments. They are expanded and echoed, which prints:
test | tee -a reports/mylog.log
on the standard output, not the effect you expected, I guess. You could, for instance, use eval. On the command line:
eval "echo "test" $REDIRECT reports/mylog.log"
Which, in your Makefile, would become:
eval "$(1) $$REDIRECT $(2)"
Next you should not quote the third parameter of call because the quotes will be passed unmodified and your script will be expanded by make as:
echo " "doing test" terminated with error $RET_CODE"
Again probably not what you want.
Third, you should avoid useless spaces in the parameters of call because they are preserved too (as you can see above between the first 2 double quotes):
.PHONY: foo
foo:
$(call call_script,echo "test",reports/mylog.log,doing test,OUTPUT_ENABLED)
And for your last desired feature, it would be slightly easier to pass the value of OUTPUT_ENABLED to call instead of its name, but let's go this way:
$ cat myfunction.mk
define call_script
set +x
mkdir -p $$(dirname $(2))
if [ ! -f $(2) ]; then
echo "" > $(2)
fi
if [ "$($(4))" = "yes" ]; then
REDIRECT='| tee -a'
else
REDIRECT='&>>'
fi
echo '>> $(1)'
eval "$(1) $$REDIRECT $(2)"
RET_CODE=$$?
echo "exit_code is: $$RET_CODE"
if [ ! $$RET_CODE = 0 ]; then
echo "$(3) terminated with error $$RET_CODE"
exit $$RET_CODE
else
if [ ! -z "$(strip $(3))" ]; then
echo "$(3) done"
fi
fi
endef
$ cat Makefile
.ONESHELL:
include myfunction.mk
OUTPUT_ENABLED ?= yes
target:
$(call call_script,echo "test",reports/mylog.log,doing test,OUTPUT_ENABLED)
Note that I moved the .ONESHELL: in the main Makefile because it is probably better to not hide it inside an included file. Up to you.

Answer 2

The most problematic issue here is that if you pipe your commands, the exit code is the exit code of the last command in a pipe, e.g false | tee foo.log will exit with 0 as tee will most probably succeed. Note also that pipe only redirects stdout, so your log will not contain any stderr messages unless explicitly redirected.
Considering that piping commands influence exit code and lack of portability of $PIPESTATUS (most specifically not being supported in dash), I would try to avoid piping commands and use a temporary file for gathering output, i.e.:
$ cat Makefile
# $(1) - script to execute
# $(2) - log file
# $(3) - description
define call_script
echo '>> $(1)'
$(if $(OUTPUT_ENABLED), \
$(1) > $#.log 2>&1; RET_CODE=$$?; mkdir -p $(dir $(2)); cat $#.log >> $(2); cat $#.log; rm -f $#.log, \
$(1); RET_CODE=$$? \
); \
echo "EXIT_CODE is: $${RET_CODE}"; \
if [ $${RET_CODE} -ne 0 ]; then $(if $(3),echo "$(3) terminated with error $${RET_CODE}";) exit $${RET_CODE}; fi; \
$(if $(3), echo "$(3) done.")
endef
good:
$(call call_script,echo "test",reports/mylog.log,doing test)
bad:
$(call call_script,mkdir /root/foo,reports/mylog.log,intentional fail)
ugly:
$(call call_script,bad_command,reports/mylog.log)
Regular call will not create the logs and will stop on errors:
$ make good bad ugly
echo '>> echo "test"'
>> echo "test"
echo "test"; RET_CODE=$? ; echo "EXIT_CODE is: ${RET_CODE}"; if [ ${RET_CODE} -ne 0 ]; then echo "doing test terminated with error ${RET_CODE}"; exit ${RET_CODE}; fi; echo "doing test done."
test
EXIT_CODE is: 0
doing test done.
echo '>> mkdir /root/foo'
>> mkdir /root/foo
mkdir /root/foo; RET_CODE=$? ; echo "EXIT_CODE is: ${RET_CODE}"; if [ ${RET_CODE} -ne 0 ]; then echo "intentional fail terminated with error ${RET_CODE}"; exit ${RET_CODE}; fi; echo "intentional fail done."
mkdir: cannot create directory ‘/root/foo’: Permission denied
EXIT_CODE is: 1
intentional fail terminated with error 1
make: *** [Makefile:19: bad] Error 1
Note that ugly was not built due to failure on bad. Now the same with the log:
$ make good bad ugly OUTPUT_ENABLED=1
echo '>> echo "test"'
>> echo "test"
echo "test" > good.log 2>&1; RET_CODE=$?; mkdir -p reports/; cat good.log >> reports/mylog.log; cat good.log; rm -f good.log; echo "EXIT_CODE is: ${RET_CODE}"; if [ ${RET_CODE} -ne 0 ]; then echo "doing test terminated with error ${RET_CODE}"; exit ${RET_CODE}; fi; echo "doing test done."
test
EXIT_CODE is: 0
doing test done.
echo '>> mkdir /root/foo'
>> mkdir /root/foo
mkdir /root/foo > bad.log 2>&1; RET_CODE=$?; mkdir -p reports/; cat bad.log >> reports/mylog.log; cat bad.log; rm -f bad.log; echo "EXIT_CODE is: ${RET_CODE}"; if [ ${RET_CODE} -ne 0 ]; then echo "intentional fail terminated with error ${RET_CODE}"; exit ${RET_CODE}; fi; echo "intentional fail done."
mkdir: cannot create directory ‘/root/foo’: Permission denied
EXIT_CODE is: 1
intentional fail terminated with error 1
make: *** [Makefile:19: bad] Error 1
$ cat reports/mylog.log
test
mkdir: cannot create directory ‘/root/foo’: Permission denied
Note that this time ugly was also not run. But if run later, it will correctly append to the log:
$ make ugly OUTPUT_ENABLED=1
echo '>> bad_command'
>> bad_command
bad_command > ugly.log 2>&1; RET_CODE=$?; mkdir -p reports/; cat ugly.log >> reports/mylog.log; cat ugly.log; rm -f ugly.log; echo "EXIT_CODE is: ${RET_CODE}"; if [ ${RET_CODE} -ne 0 ]; then exit ${RET_CODE}; fi;
/bin/sh: 1: bad_command: not found
EXIT_CODE is: 127
make: *** [Makefile:22: ugly] Error 127
$ cat reports/mylog.log
test
mkdir: cannot create directory ‘/root/foo’: Permission denied
/bin/sh: 1: bad_command: not found
Personally I am not fan of implementing logging in this way. It is complicated and it only logs output of commands, not make output itself, and only of those commands which are explicitly called to do so. I'd rather keep Makefile clean and simple and just run make 2>&1 | tee log instead to have the output logged.