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

[Peter Hutterer]

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.

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
-- 
2.17.1