Can't concatenate strings in cross-platform config

[Hi-Angel]

Steps to reproduce:

$ cat cross-compile.ini 
[binaries]
prefix = '/usr/bin/' 
cpp = prefix + 'i686-w64-mingw32-g++'
ar  = prefix + 'i686-w64-mingw32-g++'

[host_machine]
system = 'windows'
cpu_family = 'x86'
cpu = 'i686'
endian = 'little'
$ touch meson.build
$ meson cross-build --cross-file cross-compile.ini

ERROR: Malformed value in cross file variable cpp.

A full log can be found at /home/constantine/Projects/meson-test/cross-build/meson-logs/meson-log.txt

The complaint means it can't concatenate prefix with 'i686-w64-mingw32-g++' in definition of cpp. Interestingly the following line of code:

cpp = '/usr/bin/' + 'i686-w64-mingw32-g++'

works fine.

meson version 0.47.0

[nirbheek]

The file format is ini-like, so it does not support the + operator. This is a good idea though, maybe we should implement it. What do you think @jpakkane?

[QuLogic]

There are ways to do interpolation on ini-like files.

[jpakkane]

The fact that interpolation works at all is a side effect of how I implemented it back when (I was lazy). For cross files I really prefer the explicitness of just writing it out. Cross files are written once and rarely change. The issue would be different if they were constantly in flux. But they're not.

[NickeZ]

It is supported in pkg-config with ${macro} syntax.

See section "Metadata File Syntax" in https://linux.die.net/man/1/pkg-config

[jpakkane]

No dollar sign variable expansions. Ever! Under any circumstances!

[NickeZ]

So I looked in the sources and since ConfigParser is used and interpolation isn't overridden I think @QuLogic's solution should work today (unless I missed something):

[binaries]
prefix = '/usr/bin/' 
cpp = '%(prefix)s/i686-w64-mingw32-g++'
ar  = '%(prefix)s/i686-w64-mingw32-g++'

Default OptionParser is:

class configparser.ConfigParser(defaults=None, dict_type=collections.OrderedDict, allow_no_value=False, delimiters=('=', ':'), comment_prefixes=('#', ';'), inline_comment_prefixes=None, strict=True, empty_lines_in_values=True, default_section=configparser.DEFAULTSECT, interpolation=BasicInterpolation(), converters={})

[chewi]

Related to this and rather weird is the situation with arrays:

Documented but doesn't work:

c_args = ['-O1']
c_args += ['-g']

Not documented but does work!!

c_args = ['-O1'] + ['-g']

I have tested this on 0.49.0 and tried to test on git master but cross-compiling seems totally broken at the moment, like it's almost entirely ignoring the cross file.

[skrap]

The documentation says to do exactly this:

# cross.ini
[binaries]
c = arch + '-gcc'

So I suspect the docs should either be fixed, or this issue should be addressed? Or am I wildly misunderstanding something?

[xclaesse]

That works only when you pass both aarch64.ini (where arch is defined) and cross.ini.