How to generate a header file containing macros?

[TLINDEN]

I am maintaining an old c++ program which uses autoconf and automake as build system. I need to do a couple of things on the old code but don't want to fiddle around with this crap. So I want to switch to meson and ninja.

In my old setup I generated a file platform.h containing macros like HAVE_LIBPCRE etc, which is being included in the sources. So I need to replicate this somehow. This is what I have so far:

platform_h = custom_target(
    'platform_h',
    output : 'platform.h',
    command : ['./platform.sh', conf.get('HAVE_LIBPCRE'), '@OUTPUT@'],
)

The script platform.sh currently looks like this:

#!/bin/sh
echo "$@"> platform.h

When I call meson, I get:

meson setup --reconfigure build
The Meson build system
Version: 1.7.0
Source dir: /home/scip/dev/dbtool
Build dir: /home/scip/dev/dbtool/build
Build type: native build
meson.build:65: WARNING: Keyword argument "include_directories" defined multiple times.
WARNING: This will be an error in Meson 2.0.
Project name: dbtool
Project version: 1.9.1
C++ compiler for the host machine: ccache c++ (gcc 14.2.0 "c++ (Ubuntu 14.2.0-19ubuntu2) 14.2.0")
C++ linker for the host machine: c++ ld.bfd 2.44
Host machine cpu family: x86_64
Host machine cpu: x86_64
Dependency libpcre2-8 found: YES 10.45 (cached)
Library db_cxx found: YES

meson.build:43:13: ERROR: custom_target keyword argument 'command' was of type array[int | str] but should have been array[str | BuildTarget | CustomTarget | CustomTargetIndex | ExternalProgram | File] that cannot be empty

A full log can be found at /home/scip/dev/dbtool/build/meson-logs/meson-log.txt

As far as I understand the error message, the command array contained an int, probably the output of the conf.get() call, although it should be quoted according to the documentation.

I also tried to remove the conf part just to see if the script is being called at least:

platform_h = custom_target(
    'platform_h',
    output : 'platform.h',
    command : ['./platform.sh', '@OUTPUT@'],
)

In this case meson runs successful but no platform.h file is being generated at all. So it's not working anyway even if I managed to fix the conf.get() stuff somehow.

I am completely lost and have no idea how to proceed. I just need the values of the conf object translated into my platform.h.

I'd appreciate any help!

The whole repo can be found here: https://codeberg.org/scip/dbtool/src/branch/codeberg (it doesn't build yet, obviously).

Tom

[TLINDEN]

I found the to_string() function and changed the command to:

command : ['./platform.sh', conf.get('HAVE_LIBPCRE').to_string(), '@OUTPUT@'],

But the script isn't being executed by the looks of it, no platform.h can be found anywhere.

[eli-schwartz]

The direct replacement for Autotools usage of autoheader (produced config.h) is https://mesonbuild.com/Configuration.html#configuring-without-an-input-file

configure_file(output: 'platform.h', configuration_data: conf)

It will handle all details for you.

[TLINDEN]

I managed to get it to work with:

m = configure_file(
  input : 'platform.h.in',
  output : 'platform.h',
  configuration : conf,
)

[eli-schwartz]

Aside for my recommendation to use configure_file, your posted example has a slight flaw. The platform.sh script takes @OUTPUT@ as an argument in meson, but the script itself only prints all its arguments to ${PWD}/platform.h (which isn't in the build directory). If you wanted to use a script for this you'd need to echo to $1, then shift and process all remaining arguments as config values.

That explains why the file was never created when you expected it to be.