[Qbs] Qbs and debian packaging

[Wookey]

On 2017-12-20 11:09 +0100, Christian Kandeler wrote:
> On Wed, 20 Dec 2017 04:54:44 +0000
> Wookey <wookey at wookware.org> wrote:
> 
> > b) a wiki page on packaging qbs-using packages for debian-style distros:
> > https://wiki.debian.org/QBS
> > 
> > Do please tell me what's incorrect on that page 

[snip comments]

OK. Page updated, although there will be more when this conversation is finished.

You suggested 
> qbs build --no-install modules.qbs.installRoot:debian/tmp
> qbs install --no-build modules.qbs.installRoot:debian/tmp
However this breaks the build, because nothing gets installed into debian/tmp.

But this works
> qbs build --no-install modules.qbs.installRoot:debian/tmp
> qbs install --no-build --install-root debian/tmp

I had assumed that --install-root and modules.qbs.installRoot were
equivalent, but it seems they are not. Is this expected? The main
difference seems to be that --install-root creates the directory if it
doesn't exist?

> - Regarding the lib paths: I suppose something along the lines of what
>   you show there is the correct approach, though I would not necessarily
>   expect project authors to provide debian-specific hooks, but rather
>   generic ones. For instance:
>       Project {  // Or in some project-specific module
>           property string libDir: "lib"
>           // ...
>       }
>       DynamicLibrary {
>           Group {
>               fileTagsFilter: ["dynamiclibrary", "dynamiclibrary_symlink"]
>               qbs.install: true
>               qbs.installDir: project.libDir
>           }
>       }
>       $ qbs build project.libDir:lib/$DEB_HOST_MULTIARCH

OK. this works, and I agree that a generic name is better.

>   Note that "usr" should probably not be part of qbs.installDir, but
>   rather is a possible value of qbs.installPrefix.

This works if done on the command line:
qbs install modules.qbs.installPrefix:usr/ project.libDir:lib/$DEB_HOST_MULTIARCH

but not if either variable is set in the profile. They are ignored:
  qbs config --settings-dir /tmp modules.qbs.installPrefix usr/

<fx: fiddling and peering>

Ah, the namespace was wrong, it should be:
  qbs config --settings-dir /tmp profiles.default.qbs.installPrefix usr/
but using
  qbs config --settings-dir /tmp profiles.default.project.libDir lib/$(DEB_HOST_MULTIARCH)
does not work because the  
  property string libDir: "lib"
in the project file overwrites it unless that var is set on the command line. Right?

I'm confused about the namespacing. It seems to be different for the
build/install commands and the config command:
  qbs config profiles.default.cpp.linkerFlags "-z,relro"
  qbs build modules.cpp.linkerFlags:"-z,relro"

both set the linker flags in the build. I can see why there is the
"profiles.default" namespace in the config command, but why does one
have 'modules' in and not the other?
  qbs config profiles.default.modules.cpp.linkerFlags "-z,relro"
does not change the linkerFlags in the build.

Also I note that '=' in the config vlaue seems to cause a problem:
  qbs config profiles.default.cpp.defines "FORTIFY_SOURCE=2"
does not cause -DFORTIFY_SOURCE=2 in the build, it causes -D2
<fx: more fiddling> Ah. OK it needs to be suplied as a quoted list:
  qbs config profiles.default.cpp.defines '[ "FORTIFY_SOURCE=2" ]'

> > Honouring buildflags
> > --------------------
> > 

> Why not just pass the flags on the command line or put them in some sort of "packaging profile", e.g. via the qbs config command?

So I have done this, and once I worked out namespace and quoting issues it works.

The only problem is that a lot on string-munging is required to convert:

CFLAGS=-g -O2 -fstack-protector-strong -Wformat -Werror=format-security
CPPFLAGS=-Wdate-time -D_FORTIFY_SOURCE=2
CXXFLAGS=-g -O2 -fstack-protector-strong -Wformat -Werror=format-security
LDFLAGS=-Wl,-z,relro
into
  qbs config --settings-dir /tmp profiles.default.cpp.debugInformation true
  qbs config --settings-dir /tmp profiles.default.cpp.optimization fast
  qbs config --settings-dir /tmp profiles.default.cpp.commonCompilerFlags -Wdate-time
  qbs config --settings-dir /tmp profiles.default.cpp.defines '[ "FORTIFY_SOURCE=2" ]'
  qbs config --settings-dir /tmp profiles.default.cpp.cFlags '[ "-fstack-protector-strong", "-Wformat", "-Werror=format-security" ]'
  qbs config --settings-dir /tmp profiles.default.cpp.cxxFlags '[ "-fstack-protector-strong", "-Wformat" "-Werror=format-security" ]'
  qbs config --settings-dir /tmp profiles.default.cpp.linkerFlags "-z,relro"

So I can do this for a static config of current build flags, but some
work would be involved in automating this so that it still worked when
the flags changed (they do from time to time, and can be changed
per-user, per-system etc). We wouldn't want every debian rules file to
have to have a lot of boilerplate for this conversion.

A debian qbs module could presumably do the necesary munging.

The dpkg-buildflags interface is quite flexible and can select items
by 'area' (reproducible, hardening, qa, sanitize) and
vendor/system/user/env and understands prepending and appending and
setting and removing, but currently output formats are shell, cmdline
and make, so a new one for qbs would be needed for painless support,
and teaching it that defines might be wanted without the -D, or linker
options without the -Wl would be new.

I'll discuss this with the dpkg maintainers.

So, I think I have made everything work (except DEB_BUILD_OPTIONS -
I'll try that tomorrow), but only for the static case. And there are a
few clarifications requested above. Then I can update the wiki.

Wookey
-- 
Principal hats:  Linaro, Debian, Wookware, ARM
http://wookware.org/
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