[RFC PATCH libinput] tools: run list-quirks from the git data when running from the builddir

[Pekka Paalanen]

On Fri, 22 Jun 2018 12:48:53 +1000
Peter Hutterer <peter.hutterer at who-t.net> wrote:

> I'd like some comment on this from someone who knows this stuff better than
> I do. The main goal is to have the same binary default to different search
> paths, depending whether it's the installed version or the one run from the
> build directory. This is the only solution I could come up with and it
> works, but I'm not sure how much of that is coincidence vs "yes, this is how
> ELF stripping works".
> 
> Any comments welcome. Or other solutions to this. Thanks
> 
> ---
> 
> Push the git data directory into a special variable in a custom ELF section.
> Then after install, strip that ELF section out. The result is that when we're
> running from the builddir, the data path is set and we read from there. When
> running from the system install, the data path is zeroes only and we're
> running with the defaults.

Hi Peter,

this is certainly interesting. I don't know about the correctness, but
I have been wondering about how to disable the test suite scaffolding
(e.g. WESTON_MODULE_MAP env var) in an installed weston instance.

I've also been thinking about how to expose private functions from a
library for a test suite but prevent those from being accessed in an
installed version. Maybe that could be an array of function pointers
declared in a special section like you did, so it would disappear on
install.


Thanks,
pq

> 
> Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
> ---
>  meson.build                     |  5 +++++
>  tools/libinput-list-quirks.c    | 12 ++++++++++++
>  tools/strip-builddir-section.sh | 18 ++++++++++++++++++
>  3 files changed, 35 insertions(+)
>  create mode 100644 tools/strip-builddir-section.sh
> 
> diff --git a/meson.build b/meson.build
> index b650bbde..0b9dc751 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -479,6 +479,11 @@ libinput_list_quirks = executable('libinput-list-quirks',
>  				  install_dir : libinput_tool_path,
>  				  install : true
>  				 )
> +meson.add_install_script('tools/strip-builddir-section.sh',
> +			 libinput_tool_path,
> +			 'libinput-list-quirks')
> +
> +
>  test('validate-quirks',
>       libinput_list_quirks,
>       args: ['--validate-only', '--data-dir=@0@'.format(join_paths(meson.source_root(), 'data'))]
> diff --git a/tools/libinput-list-quirks.c b/tools/libinput-list-quirks.c
> index 533c4f3a..1207ade3 100644
> --- a/tools/libinput-list-quirks.c
> +++ b/tools/libinput-list-quirks.c
> @@ -207,6 +207,13 @@ usage(void)
>  	       "	Validate the database\n");
>  }
>  
> +/* When running from builddir, we use the git data tree by default.
> +   This section is stripped on install.
> + */
> +static const char builddir_data_path[]
> +	__attribute__ ((section ("builddir_section")))
> +	= LIBINPUT_DATA_SRCDIR;
> +
>  int
>  main(int argc, char **argv)
>  {
> @@ -219,6 +226,11 @@ main(int argc, char **argv)
>  	struct quirks_context *quirks;
>  	bool validate = false;
>  
> +	/* After the section is stripped, builddir_data_path is zeroes */
> +	data_path = builddir_data_path;
> +	if (data_path && strlen(data_path) == 0)
> +		data_path = NULL;
> +
>  	while (1) {
>  		int c;
>  		int option_index = 0;
> diff --git a/tools/strip-builddir-section.sh b/tools/strip-builddir-section.sh
> new file mode 100644
> index 00000000..dbae7964
> --- /dev/null
> +++ b/tools/strip-builddir-section.sh
> @@ -0,0 +1,18 @@
> +#!/bin/bash
> +#
> +# Usage: strip-builddir-section /path/to/libexec/libinput file1 file2
> +
> +directory=$1
> +shift
> +
> +files="$@"
> +
> +pushd $directory > /dev/null
> +for file in $files; do
> +	if test -e $file; then
> +		echo "Stripping file $directory/$file"
> +		objcopy --remove-section builddir_section $file $file.tmp
> +		mv $file.tmp $file
> +	fi
> +done
> +popd > /dev/null

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