Pkg xen devel - Dec 2020 - [PATCH 06/19] d/shuffle-binaries: Fix binary shuffling script for cross-building

On 7/17/20 8:37 AM, Elliott Mitchell wrote:
> `ldd` doesn't work with cross-builds, so use `file` to detect scripts
> and `strings | grep` for identifying linked libraries.  Even though
> debhelper depends on file, make the requirement explicit.
> 
> Heavily simplify script inner loop.  While the core of that inner loop
> was often executed only once, it is best to shrink inner loops.
> 
> Signed-off-by: Elliott Mitchell <ehem+debian at m5p.com>
> ---
>  debian/control          |  1 +
>  debian/shuffle-binaries | 31 ++++++++++++++++---------------
>  2 files changed, 17 insertions(+), 15 deletions(-)
> 
> diff --git a/debian/control b/debian/control
> index 942bf6711c..90007f6a02 100644
> --- a/debian/control
> +++ b/debian/control
> @@ -6,6 +6,7 @@ Section: admin
>  Standards-Version: 4.5.0
>  Build-Depends:
>     debhelper (>= 10),
> +   file,
>     dh-exec,
>     dpkg-dev (>= 1.16.0~),
>     rdfind,
> diff --git a/debian/shuffle-binaries b/debian/shuffle-binaries
> index 37176d26e7..03b4bc4794 100755
> --- a/debian/shuffle-binaries
> +++ b/debian/shuffle-binaries
> @@ -24,28 +24,29 @@ mkdir -p "$t/$vd"
>  
>  find "$t"/usr/*bin -type f | while read binary; do
>  
> -	reason=''
> -	{ ldd "$binary" ||: ; } | { fgrep '=>' ||: ; } \
> -	| (
> -		while read lib dummy; do
> +	# filter for executables (ignore scripts)
> +	file "$binary" | grep -q -eELF.\\+version.\\+interpreter ||
continue
> +
> +	# ldd doesn't work for cross-building
> +	reason=$(
> +		strings "$binary" | grep -e^lib.\\+\\.so\\.\[.0-9\]\\+\$ | \
> +		while read lib; do
>  			lib=${lib%.so.*}
> -			if grep -F "usr/lib/*/$lib.so.*" $list >/dev/null; then
> -				reason+=" $lib"
> +			if grep -q -F "usr/lib/*/$lib.so.*" $list; then
> +				printf " %s" "$lib"
>  			fi
>  		done
> +	)
>  
> -		if [ "x$reason" = x ]; then
> -			exit 0
> -		fi
> +	# if no reason, then skip
> +	[ -n "$reason" ] || continue
>  
> -		echo "shuffling $binary $reason"
> +	echo "shuffling $binary$reason"
>  
> -		leaf=${binary##*}
> -		mv -v $binary $t/$vd/$leaf
> -		ln -vs $cd/xen-utils-wrapper $binary
> +	mv -v "$binary" "$t/$vd/"
> +	ln -vs "$cd/xen-utils-wrapper" "$binary"
>  
> -		touch debian/shuffle-binaries.stamp
> -	)
> +	touch "$0.stamp"
>  done
>  
>  if [ ! -e "$0.stamp" ]; then
> 
Ok, this one does not apply:

~/build/xen/debian-xen k (knorrie/sid) 0-$ git am -3
20201204-2028-ehem/06\ d_shuffle-binaries\:\ Fix\ binary\ shuffling\
script\ for\ cross-building\ -\ Elliott\ Mitchell\
\<ehem+debian at m5p.com\>\ -\ 2020-07-17\ 0837.eml
Applying: d/shuffle-binaries: Fix binary shuffling script for cross-building
error: sha1 information is lacking or useless (debian/shuffle-binaries).
error: could not build fake ancestor
Patch failed at 0001 d/shuffle-binaries: Fix binary shuffling script for
cross-building
hint: Use 'git am --show-current-patch' to see the failed patch
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am
--abort".

When I use git am --show-current-patch I get a big pile of crap because
you're not using git send-email.

I don't know what to do with this now.

Hans

On Fri, Dec 04, 2020 at 10:04:35PM +0100, Hans van Kranenburg
wrote:
> When I use git am --show-current-patch I get a big pile of crap because
> you're not using git send-email.
> 
> I don't know what to do with this now.
Strong indicator of a missing patch.  In this case you got 1-4, but then
missed #5 and started on #6.  #5 and #6 don't modify the same lines, but
they modify lines next together and thus missing #5 kills the context
lines for #6.

Eventually you'll learn how to read patches whether you want to or not.
As such, a quick overview of the format:

--- a/debian/shuffle-binaries
+++ b/debian/shuffle-binaries
@@ -22,7 +22,7 @@ cd=/usr/lib/xen-common/bin
 
 mkdir -p "$t/$vd"
 
-for binary in `find $t/usr/{bin,sbin} -type f`; do
+find "$t"/usr/*bin -type f | while read binary; do
        # filter for executables (ignore scripts)
        file "$binary" | grep -q -eELF.\\+version.\\+interpreter ||
continue
 
--end

The first two are the source and destination files, plus a triple
repetition of their respective prefixes.  Most often '-' is used for
source and '+' is used for destination and the source is listed before
destination, but the format *DOES* *NOT* require this!  Though now that
I've tried, `git am` doesn't like anything other than '-' for
source and
'+' for destination (`patch` is perfectly happy with '%' and
'$').

Hunks start with "@@".  The '-' is the character used for the
source
file, the '+' is the character used for the destination file.  The first
number is the line number from the respective file, the second is the
number of lines included from that file.

The following lines start with one of 3 characters.  Space is for lines
which are identical between both files.  If a line starts with the source
prefix, then that line is *only* present in the source file.  If a line
starts with the destination prefix, then that line is *only* present in
the destination file.

This likely isn't the greatest description of the patch format.  Your
favored search engine can find other descriptions of the "patch" or
"unified diff" format.  For reference, the below is considered
*identical* to the above:

### b/debian/shuffle-binaries
zzz a/debian/shuffle-binaries
@@ z22,7 #22,7 @@ cd=/usr/lib/xen-common/bin
 
 mkdir -p "$t/$vd"
 
zfor binary in `find $t/usr/{bin,sbin} -type f`; do
#find "$t"/usr/*bin -type f | while read binary; do
        reason=''
        { ldd "$binary" ||: ; } | { fgrep '=>' ||: ; } \
        | (
--end

`diff -u $src $dst` can generate the same result.  Generally
source/destination filenames include the parent directory.  Any patch
acceptable to `git am` can also be applied using `patch -p1 < $file`

If you're doing this long enough you'll learn the basics of the patterns
since humans are great at pattern recognition and at some point you'll
need to deal with a funky patch due to wanting its result.

Perversions like the above are rare, but the format (though not `git am`)
allows it (yes, prior to sending this message I tested with `patch -p1`).


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