Solemn's Site
Buggy software since 200X
Home

Welcome

Welcome to the site of solemnwarning (Daniel Collins), here you will find software and other debris I've published over the years.

Latest posts

Capturing errors from the $(shell ...) function

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)))

Comments (0)

Serving static gzip-compressed content with Apache

Posted in Linux on 28 Mar 2019 at 18:49 UTC

The CI pipeline for one of my projects generates coverage reports as a collection of HTML files, which are published on one of my web servers. Each report is only ~8MB, but that starts to add up pretty quickly after a few dozen commits, so I wanted to compress the reports on disk and have them decompressed as needed rather than using up my precious disk space.

Strangely, this doesn't seem to be a widely-used (or at least well-documented) Apache configuration. All references I found were out of date or didn't do what I wanted.

So here's how I got it working...

Read more...

Comments (0)

IPXWrapper testing infrastructure

Posted in programming on 06 Mar 2018 at 21:39 UTC

In 2014 I wrote a fairly comprehensive test suite for IPXWrapper, which tests it end-to-end, from the APIs through to the network traffic they generate and process. It depends on a meticulously configured set of Windows and Linux machines, which I had duplicated using several different versions of Windows.

Eventually bit-rot set in and some of the Windows VMs became unusable for quick testing; sat installing updates whenever I booted them, broke themselves in odd ways, etc. Also my workstation doesn't have enough RAM for Chrome and several Windows VMs at the same time. No machine does.

...

Read more...

Comments (0)

struct XXX redeclared with different access

Posted in programming on 22 Dec 2017 at 15:29 UTC

Today I was writing some C++ and wanted to add a private struct within a class for storing some data, but not just any struct - I wanted a private abstract base struct with a couple of implementations.

So I wrote something like this:

...

That didn't compile, GCC gave me the following error and Google wasn't terribly helpful when I searched for it:

/home/solemnwarning/test.cpp:8:3: error: ‘struct Thing::PrivateAbstract::A’ redeclared with different access

...

Read more...

Comments (0)