Posted in programming on 07 Oct 2019 at 18:48 UTC
The GNU Make
shell function executes a shell command, expanding to whatever it wrote to standard output. If the command fails, thats just fiiine - however much it did or didn't output is what you get.
command_output := $(shell command)
I use the shell function for (among other things) getting compiler flags necessary for using libraries (e.g. from
pkg-config), and Make's behaviour of ignoring these errors is rather annoying, since it can mask the actual error with pages of output before getting to a build command that actually fails. Sometimes it can even mess up the compiler flags to the point you (or at least I) spend ages hunting down a phantom problem that doesn't exist.
Weirdly, I couldn't find any good solution on the web, with a bit of experimentation I wound up developing the following macro:
# Wrapper around the $(shell) function that aborts the build if the command # exits with a nonzero status. shell-or-die = \ $(eval sod_out := $(shell $(1); echo $$?)) \ $(if $(filter 0,$(lastword $(sod_out))), \ $(wordlist 1, $(shell echo $$(($(words $(sod_out)) - 1))), $(sod_out)), \ $(error $(1) exited with status $(lastword $(sod_out)))) WX_CXXFLAGS := $(call shell-or-die,wx-config --cxxflags base core aui propgrid adv) WX_LIBS := $(call shell-or-die,wx-config --libs base core aui propgrid adv)
If you don't mind depending on GNU Make 4.2 (a bit too new for my tastes), if can be simplified to:
shell-or-die = \ $(eval sod_out := $(shell $(1))) \ $(if $(filter 0,$(.SHELLSTATUS)), \ $(sod_out), \ $(error $(1) exited with status $(.SHELLSTATUS)))
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