Re: [Qemu-devel] [PATCH] tests: Handle $RANDOM not being supported by the shell

[Markus Armbruster <armbru@redhat.com>]

Peter Maydell <peter.maydell@linaro.org> writes:

> In various places in our test makefiles and scripts we use the
> shell $RANDOM to create a random number. This is a bash
> specific extension, and doesn't work on other shells.
> With dash the shell doesn't complain, it just effectively
> always evaluates $RANDOM to 0:
>   echo $((RANDOM + 32768))     => 32768
>
> However, on NetBSD the shell will complain:
>   "-sh: arith: syntax error: "RANDOM + 32768"
>
> which means that "make check" fails.
>
> Switch to using "${RANDOM:-0}" instead of $RANDOM,
> which will portably either give us a random number or zero.

Golden opportunity to implement https://www.xkcd.com/221/

> This means that on non-bash shells we don't get such
> good test coverage via the MALLOC_PERTURB_ setting, but
> we were already in that situation for non-bash shells.
>
> Our only other uses of $RANDOM (in tests/qemu-iotests/check
> and tests/qemu-iotests/162) are in shell scripts which use
> a #!/bin/bash line so they are always run under bash.
>
> Suggested-by: Eric Blake <eblake@redhat.com>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  tests/Makefile.include | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tests/Makefile.include b/tests/Makefile.include
> index 6d6cb74..f6310d2 100644
> --- a/tests/Makefile.include
> +++ b/tests/Makefile.include
> @@ -826,7 +826,7 @@ $(patsubst %, check-qtest-%, $(QTEST_TARGETS)): check-qtest-%: $(check-qtest-y)
>  	$(if $(CONFIG_GCOV),@rm -f *.gcda */*.gcda */*/*.gcda */*/*/*.gcda,)
>  	$(call quiet-command,QTEST_QEMU_BINARY=$*-softmmu/qemu-system-$* \
>  		QTEST_QEMU_IMG=qemu-img$(EXESUF) \
> -		MALLOC_PERTURB_=$${MALLOC_PERTURB_:-$$((RANDOM % 255 + 1))} \
> +		MALLOC_PERTURB_=$${MALLOC_PERTURB_:-$$(( $${RANDOM:-0} % 255 + 1))} \
>  		gtester $(GTESTER_OPTIONS) -m=$(SPEED) $(check-qtest-$*-y) $(check-qtest-generic-y),"GTESTER","$@")
>  	$(if $(CONFIG_GCOV),@for f in $(gcov-files-$*-y) $(gcov-files-generic-y); do \
>  	  echo Gcov report for $$f:;\
> @@ -837,7 +837,7 @@ $(patsubst %, check-qtest-%, $(QTEST_TARGETS)): check-qtest-%: $(check-qtest-y)
>  $(patsubst %, check-%, $(check-unit-y)): check-%: %
>  	$(if $(CONFIG_GCOV),@rm -f *.gcda */*.gcda */*/*.gcda */*/*/*.gcda,)
>  	$(call quiet-command, \
> -		MALLOC_PERTURB_=$${MALLOC_PERTURB_:-$$((RANDOM % 255 + 1))} \
> +		MALLOC_PERTURB_=$${MALLOC_PERTURB_:-$$(( $${RANDOM:-0} % 255 + 1))} \
>  		gtester $(GTESTER_OPTIONS) -m=$(SPEED) $*,"GTESTER","$*")
>  	$(if $(CONFIG_GCOV),@for f in $(gcov-files-$(subst tests/,,$*)-y) $(gcov-files-generic-y); do \
>  	  echo Gcov report for $$f:;\

A possible alternative might be putting

    export RANDOM = 4    # chosen by a fair dice roll

into the makefile.

There's another occurence in tests/qemu-iotests/162.