Hi Chris,
On 06/06/2018 05:23, Chris Packham wrote:
Hi,
On Tue, Jun 5, 2018 at 2:08 AM Luca Ceresoli luca@lucaceresoli.net wrote:
The commands in if_changed and if_changed_dep are concatenated with a ';', thus any error in any command except the last one will be silently ignored. This is particularly relevant for the actual payload, cmd_$(1), whose errors should not be unnoticed.
Fix by replacing the ';' with '&&'.
Signed-off-by: Luca Ceresoli luca@lucaceresoli.net
Note: I'm not aware of any situation in which this bug has any visible effect. I noticed the problem while working on a different topic, but later I did that job in a different way, not involving if_changed usages. But this is a bug anyway, so let's fix it.
scripts/Kbuild.include | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include index 2c7918ad3721..f722f75611df 100644 --- a/scripts/Kbuild.include +++ b/scripts/Kbuild.include @@ -255,16 +255,16 @@ any-pThis is tricky, arereq = $(filter-out $(PHONY),$?) $(filter-out $(PHONY) $(wildcard $^),$^) # Execute command if command has changed or prerequisite(s) are updated. # if_changed = $(if $(strip $(any-prereq) $(arg-check)), \
@set -e; \$(echo-cmd) $(cmd_$(1)); \
@set -e; \$(echo-cmd) $(cmd_$(1)) && \ printf '%s\n' 'cmd_$@ := $(make-cmd)' > $(dot-target).cmd)# Execute the command and also postprocess generated .d dependencies file. if_changed_dep = $(if $(strip $(any-prereq) $(arg-check) ), \
@set -e; \$(echo-cmd) $(cmd_$(1)); \scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(dot-target).tmp;\rm -f $(depfile); \
@set -e; \$(echo-cmd) $(cmd_$(1)) && \scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(dot-target).tmp && \rm -f $(depfile) && \ mv -f $(dot-target).tmp $(dot-target).cmd)# Usage: $(call if_changed_rule,foo)
The 'set -e' should cause the sub-shell to exit immediately if any of the commands fail, regardless of the ';' vs '&&'.
Thanks for your comment, it triggered me to go deeper in understanding the issue. Apologies for not having clarified it all in the first place.
Actually ';' and '&&' are not treated the same way. The bash manpage states about 'set -e':
The shell does not exit if the command that fails is [...] part of any command executed in a && or || list except the command following the final && or ||
The issue I had initially happened when I wrote something like this:
cmd_mkimage = test -r /no/such/file && \ $(objtree)/tools/mkimage $(MKIMAGEFLAGS_$(@F)) -d $< $@ \ >$(MKIMAGEOUTPUT) $(if $(KBUILD_VERBOSE:0=), && cat $(MKIMAGEOUTPUT))
If the 'test' command fails, set -e won't stop the build. But replacing '&&' with ';' makes the build stop immediately as expected. So I guess cmd_mkimage is just meant to be used with ';'.
Assuming I'm wrong above, this patch should probably go to the kbuild mailing list http://vger.kernel.org/vger-lists.html#linux-kbuild