make it possible to build reproducibly

[mirabilos]

By default, the date and time of the build are embedded into the binary as sort of origin/version/etc. marker. This is not, however, reproducible. This patch makes it so that packagers can define a præprocessor macro, ANTIMICROX_PKG_VERSION, to a C string which is then used instead; if this macro is not defined nothing changes.

The diff comes from Debian; by upstreaming the new string can be translated.

Example use: add -DANTIMICROX_PKG_VERSION=\"'3.1.4-1 (Debian sid/amd64)'\" to CPPFLAGS. Check the Hel̲p → A̲bout dialogue, tab Info, second line, to see its effect.

[pktiuk]

During compilation i get:

/home/pawel/antimicrox/src/aboutdialog.cpp:64:64: warning: character constant too long for its type
   64 |     finalInfoText.append(tr("compiled from packaging: %1").arg(ANTIMICROX_PKG_VERSION));

[pktiuk]

It works nicely when integrated with CMake
add_compile_definitions(ANTIMICROX_PKG_VERSION="3.1.4-1 \(Debian sid/amd64\)")

I will merge it with master and later (maybe today) I will integrate it with CMake and our CI and mention it in docs

[mirabilos]

Yes, you need a string constant, so for a compiler commandline something like c++ -DANTIMICROX_PKG_VERSION=\"foo\ bar\" or =\""foo bar"\" or ="\"foo bar\"" or ='"foo bar"' or =\"'foo bar'\"; that is shell-escaped and of course needs to be adjusted for the build system you use around the invocations.

In debian/rules I actually need to input the shell-escaped versions, and the canonical form for passing string constants to builds (i.e. the one that fails the least with various tools (hand-written Makefiles, autoconf, …)) is =\"foo\" so I just did =\"${var}\" except I needed to shell-escape the $var content so =\"${var:Q}\" in BSD make, or the GNU make variant =\"$(call shellescape,${OUR_VSN})\" with the helper macro…

shellescape='$(subst ','\'',$(1))'
shellexport=$(1)=$(call shellescape,${$(1)})

… defined to emulate something BSD make can do natively.

Glad it helps!