[Buildroot] [PATCH 01/15] package/pkg-generic.mk: detect files overwritten in TARGET_DIR and HOST_DIR

Hi,

On Mon, 21 Jun 2021 23:31:40 +0200
"Yann E. MORIN" [off-list ref] wrote:

[...]

quoted

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>  

From here...

quoted

This commit is retreived from Thomas's work.
The first version was discussed
https://patchwork.ozlabs.org/project/buildroot/patch/20200430095249.782597-9-thomas.petazzoni at bootlin.com/
This new version was not already submitted by Thomas or I missed it.  

... to here: this should have been a post-commit note, after the ---
line...

quoted

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---  

... here.

Additionally, it would have been nice to summarise the changes made
between the original submission and htis new one, and how the previous
review was handled.

I moved the note after a '---' line and added:

   Compared to the first version, this patch has an improved commit message and
   generates the md5sum snapshot using
     'find -L $(1) -type f -print0 | xargs -0 -r md5sum > $($(PKG)_DIR)/.files$(2).md5;'
   instead of
     'cd $(1); LC_ALL=C find . -type f -exec md5sum {} \; > $($(PKG)_DIR)/.files$(2).md5'

quoted

 package/pkg-generic.mk | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/package/pkg-generic.mk b/package/pkg-generic.mk
index 45589bcbb4..bb9ff4150a 100644
--- a/package/pkg-generic.mk
+++ b/package/pkg-generic.mk

@@ -102,6 +102,25 @@ define fixup-libtool-files
 endef
 endif
 
+# Functions to detect overwritten files
+
+ifeq ($(BR2_PER_PACKAGE_DIRECTORIES),y)
+# $(1): base directory to search in
+# $(2): suffix of file (optional)
+define pkg_detect_overwrite_before
+	LC_ALL=C find $(1) -type f -print0 | xargs -0 -r md5sum > $($(PKG)_DIR)/.files$(2).md5;
+endef
+
+# $(1): base directory to search in
+# $(2): suffix of file (optional)
+define pkg_detect_overwrite_after
+	if test -s $($(PKG)_DIR)/.files$(2).md5 ; then \
+		LC_ALL=C md5sum --quiet -c $($(PKG)_DIR)/.files$(2).md5 || \
+		{ echo "ERROR: package $($(PKG)_NAME) has overwritten files installed by a previous package, aborting."; exit 1; } ; \
+	fi
+endef
+endif  

And now I see that only part of the problem is handled; it only tries
and detect files which content changes; it does not account for files
which type did change. I.e. a symlink that was onverted over to a file,
or the other way around.

So I think we could change the pkg_detect_overwrite_before macro thusly;

    LC_ALL=C find -L $(1) -type f -print0 |...

I added '-L' option.

That should cover both cases, with just the esception that a symlink is
replaced with a file of the same content (or the other way around).
There's just a little quirk, though:

    find: File system loop detected; ?host/usr? is part of the same file
    system loop as ?host?.

Meh, that's starting to be a bit hairy... We can just ignore it
explicitly, maybe? For merged-usr in target, we should not have that
problem, but there is still the option for a custom skeleton, where
people could provide it as well...

So, to summarise: this patch does not cover all cases, but it is still
acceptable, and brings in the necessary infra that we can later extend
should the need arises.

Ok, v2 with the changes I mentioned will be sent.

Thanks for the review,
Herv? Codina

-- 
Herv? Codina, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com