PostScript Printer Description (ppd) files
describe printer features and capabilities.
They are usually evaluated by CUPS to convert
print jobs into a format suitable for a printer.
The conversion is often accomplished by commands
or even short shell scripts inside the ppd files.
ppd files are included in many printer driver packages.
Their scripts sometimes refer to other executables;
some of them are more common (like `perl`),
others are more exotic (like `rastertohp`).
If an executable is called with its name alone,
the effects of the ppd file depend on whether
the executable is in the PATH of CUPS,
and on the executable's version.
If an executable is called with an absolut path
(like `/usr/bin/perl`), it won't work at all in NixOS.
The commit at hand adds a setup hook that uses
the `fixupPhase` to substitute certain executable's
invocations in pdd files with absolute paths.
To use it, add the hook to `nativeBuildInputs` and
provide a list of executable names in `ppdFileCommands`.
Each executable must be available in the
package that is being built, or in `buildInputs`.
The setup hook's script then looks for ppd files in
`share/cups/model` and `share/ppds` in each output,
and replaces executable names with their absolute paths.
If ppd files need to be patched in unorthodox locations or
the setup hook needs to be invoked manually for other reasons,
one may leave the list `ppdFileCommands` empty to
avoid automatic processing of ppd files, then call
the shell function `patchPpdFileCommands` directly.
Details are described in the file `patch-ppd-hook.sh`.
Notes on the motivation for this setup hook:
Most packages in nixpkgs that provide
ppd files do not patch those ppd files at all.
This is not fatal when the executables are just called
with their names since the user can add packages
with the executables to `services.printing.drivers`.
E.g. if the user adds `pkgs.perl`, then all ppd
files that invoke `perl` will work as expected.
Nevertheless, to make these ppd files independent of
their execution environment, command invocations should
be substituted with absolut paths into the nix store.
This is similar to patching shebang lines so scripts can be
called independently of having the interpreter in the PATH.
The hook script in this commit is meant to support new packages
`foomatic-db*` which will generate several thousands of
ppd files referencing a plethora of different executables.
During development of these packages, I realized that
it's quite hard to patch ppd files in a robust way.
While binary names like `rastertokpsl` seem to be sufficiently
unique to be patched with `sed`, names like `date` or `gs`
are hard to patch without producing "false positives",
i.e., coincidental occurences of the executable's name that do
*not* refer to the executable and should not be patched at all.
As this problem also affects other packages,
it seems reasonable to put a robust implementation
in its own setup hook so that other
packages can use it without much effort.
Notes on the implementation:
The ppd file format is far from trivial.
The basic structure are key-value pairs;
keys may occur multiple times.
Only a small subset of keys may contain
executable names or shell scripts in their values.
Some values may span multiple lines;
a linebreak might even occur in the middle of a token.
Some executable names also occur in other keys by accident
where they must not be substituted (e.g. `gs` or `date`).
It is necessary to provide the list of command
names that will be patched for two reasons:
ppd files often contain "tokens" that might look
like commands (e.g. "file" or "host") but aren't;
these would erroneously get patched.
Also, looking for everything that might be a command
would slow down the patching process considerably.
The implementation uses `awk` to detect
keys that might contain executable names;
only their values are treated for substitution.
This avoids most cases of "overzealous" substitutions.
Since values may span multiple lines,
`sed` alone (while faster than `awk`) cannot focus
its substitution capabilities on relevant keys.
An elaborate set of regular expressions further helps
to minimize the probability of "false positives".
Several tricks are employed to speed up `awk`.
Notably, relevant files are identified with
`grep` before `awk` is applied to those files only.
Note that the script probably cannot handle fancy command
names (like spaces or backslashes as part of the name).
Also, there are still edge cases that the script would
mistakenly skip, e.g. if a shell script contains a
line break in the middle of an executable's name;
although ppd files permit such constellations,
I have yet to see one.
ppd files may be gzipped.
The setup hook accepts gzipped ppd files:
It decompresses them, substitutes paths, then recompresses them.
However, Nix cannot detect substituted paths as
runtime dependencies in compressed ppd files.
To ensure substituted paths are propagated as
runtime dependencies, the script adds each substituted
path to the variable `propagatedBuildInputs`.
Since this might not be enough for multi-output packages,
those paths are also written directly to
`nix-support/propagated-build-inputs`.
See the comment in `patch-ppd-hook.sh` for details.
Finally, the setup hook comes with a small test that
probes some edge cases with an artificial ppd file.
References:
* https://www.cups.org/doc/spec-ppd.html
* general ppd file specification
* lists some keys that may contain
executable names or shell scripts
* https://refspecs.linuxfoundation.org/LSB_4.0.0/LSB-Printing/LSB-Printing/ppdext.html
* lists some keys that may contain
executable names or shell scripts
* https://en.wikipedia.org/wiki/PostScript_Printer_Description#CUPS
* lists the usual locations of ppd files
One significant use case is adding `passthru.tests` to setup-hooks,
and help increase test coverage for mission-critical setup-hooks.
As `meta`, `passthru` doesn't go into the build script directly.
However, passing an empty set to `passthru` breaks nixpkgs-review
and OfBorg tests, so pass it only when specified.
Before the change separate-debug-info.sh did the stripping itself.
This scheme has a few problems:
1. Stripping happens only on ELF files. *.a and *.o files are skipped.
Derivations have to do it manually. Usually incorrectly
as they don't run $RANLIB (true for `glibc` and `musl`).
2. Stripping happens on all paths. Ideally only `stripDebugList` paths
should be considered.
3. Host strip is called on Target files.
This change offloads stripping logic to strip hook. This strips more
files for `glibc` and `musl`. Now we can remove most $STRIP calls
from individual derivations.
Co-authored-by: Sandro <sandro.jaeckel@gmail.com>
The initial intent was to strip .a and .o files, not .a.o files.
While at it expanded stripping for $lib output as well.
Without the change `libgcc.a` was not stripped and `.debug*` sections
made into final binaries. It's not a problem on it's own, but it's an
unintended side-effect. Noticed on `crystal_1_0` test failure where
`crystal` was not able to handle `dwarf-5`.
While at it allowed absolute file names to be passed to stripDebugList
and friends.
'strip' does not normally preserve archive index in .a files.
This usually causes linking failures against static libs like:
$ nix build --no-link -f. pkgsCross.mingw32.re2c
> ...-i686-w64-mingw32-binutils-2.38/bin/i686-w64-mingw32-ld:
/nix/store/...-i686-w64-mingw32-stage-final-gcc-13.0.0-lib/i686-w64-mingw32/lib/libstdc++.dll.a:
error adding symbols: archive has no index; run ranlib to add one
We restore the index by running ranlib explicitly.
This change mimics existing strip{All,Debug}List variables to
allow special stripping directories just for Target.
The primary use case in mind is gcc where package has to install
both host and target ELFs. They have to be stripped by their own
strip tools accordingly.
Co-authored-by: Rick van Schijndel <Mindavi@users.noreply.github.com>
Co-authored-by: Sandro <sandro.jaeckel@gmail.com>
Since 1ac53985 "*-wrapper; Switch from `infixSalt` to `suffixSalt`"
(2020) 'TARGET_' prefix (and infix) is no more. '_FOR_TARGET' suffix
is the only used suffix for target-specific tools and flags.
Use that in stip instead of always-empty variable.
A function to generate pkg-config files for Nix packages that need to create them ad hoc,
like blas and lapack.
Inspiration taken from `makeDesktopItem`.
By default, Cargo will only enable line tables. -g enables full debug
info. The RUSTFLAGS environment variable is examined by Cargo,
similar to how the NIX_*FLAGS* variables are examined by our compiler
wrappers.
A small shell script that can be used to extract a binary wrapper's
makeCWrapper call from its embedded docstring, without depending on
makeBinaryWrapper.
This commit fixes precise dependency ignorance by converting the
environment variable `autoPatchelfIgnoreMissingDeps` into a bash array
`ignoreMissingDepsArray`, passing `"${ignoreMissingDepsArray[@]}"`
instead of `"${autoPatchelfIgnoreMissingDeps[@]}"` to the python
script.
The original implementation does not work when
`autoPatchelfIgnoreMissingDeps` contains multiple dependency names.
Because it mistakenly passes `"${autoPatchelfIgnoreMissingDeps[@]}"`
to the python script. According to the Nix manual
(https://nixos.org/manual/nix/stable/expressions/derivations.html),
lists of strings are concatenated into whitespace-separated strings,
then passed to the builder as environment variables. So, if
`autoPatchelfIgnoreMissingDeps = [ "dep1" "dep2" "dep3" ]`,
`"${autoPatchelfIgnoreMissingDeps[@]}"` will be expanded to a single
argument `"dep1 dep2 dep3"`, which is not the intended behavior,
because the python script takes the long argument as a dependency
name.
With this commit, `"${ignoreMissingDepsArray[@]}"` will be expanded to
three arguments `"dep1" "dep2" "dep3"` arguments as expected, fixing
the issue.
Desktop files are only useful when accompanied by the binaries they
specify. So it makes more sense to put them next to the binaries rather
than `$out` which only usually contains the binaries.
Similar to the implementation of the `%f` and `%u` field codes. In this
case the amount of arguments passed poses no problem but the position
could, at least in theory.
This finishes the implementation of all the non-deprecated field codes.
As a part of that, repetitions of field codes are left alone. Originally
all field codes were removed. Now we replace only the first occurence.
This is correct for at least `%f`, `%u`, `%F` and `%U` because at most
one of them is permitted.
Shortcomings:
1. We replace `%[cfFikuU]` patterns one at a time. This means if the
right field code appears as part of the rest of the `Exec` field or
in a field code that was substituted earlier.
2. If any field code is repeated, only the first occurence is
substituted.
`%f` and `%u` are used to signal the program only accepts a single file
or URI argument. I do not believe there's a way to signal this
information to macOS but it is possible the program really won't work if
multiple files are passed and it's possible the relative position of
`%i`, `%c` or `%k` matters. So we replace `%f` or `%u` with `$1`. That
way we only pass one file in the (possibly significant) position of the
field code.
