Meson needs -Dbuildtype=custom to change the optimisation & debug values

[aidan-gallagher]

Overview

According to the documentation you should be able to independently set the optimisation and debug levels by passing -Debug and -Doptimization. However you actually have to pass -Dbuildtype=custom as well.

From the docs:
"For setting optimization levels and toggling debug, you can either set the buildtype option, or you can set the optimization and debug options which give finer control over the same. Whichever you decide to use, the other will be deduced from it. For example, -Dbuildtype=debugoptimized is the same as -Ddebug=true -Doptimization=2 and vice-versa."

"All other combinations of debug and optimization set buildtype to 'custom'"

Steps

Given debug set to true and optimisation set 1

$ meson setup -Ddebug=true -Doptimization=1 build

When I check the values

$ cd build
$ meson configure
...
  Core options        Current Value        Possible Values                                               Description
  ------------        -------------        ---------------                                               -----------
...
  buildtype           release              [plain, debug, debugoptimized, release, minsize, custom]      Build type to use
  debug               false                [true, false]                                                 Debug
...
  optimization        3                    [0, g, 1, 2, 3, s]                                            Optimization level
...

Then I expect buildtype=custom, debug=true, optimisation=1

Environment

$ meson --version
0.53.2

[albfan]

I can confirm in

$ meson --version
0.62.2

this is still true.

I'm testing with a vala project. If buildtype has debug true, valac uses -g and add line directives to generated source code.

$ mkdir example
$ cd example
$ meson init -l vala
$ meson -Ddebug=false -Doptimization=0 build
$ meson introspect --buildoptions build | jq '.[] | select(.name == "buildtype").value'
"debug"
$ ninja -C build
$ grep -qR "#line" build && echo YES line directives
YES line directives

Doing again with buildtype=custom works but there's a funny warning:

$ rm -rf build
$ meson -Ddebug=false -Doptimization=0 --buildtype=custom build

WARNING: Recommend using either -Dbuildtype or -Doptimization + -Ddebug. Using both is redundant since they override each other. See: https://mesonbuild.com/Builtin-options.html#build-type-options
The Meson build system
Version: 0.62.2
....
$ meson introspect --buildoptions build | jq '.[] | select(.name == "buildtype").value'
"custom"
$ ninja -C build
$ grep -qR "#line" build || echo NO line directives
NO line directives

I'm trying to setup this with an option but looks I need to set two which is annoying:

meson.build:

if get_option('plain_debug')
  if get_option('buildtype') != 'plain'
    error('set buildtype=plain to use option plain_debug')
  endif
  add_global_arguments('-g', language:'c')
endif

I'm looking for something like:

if get_option('plain_debug')
  set_option('debug', false)
  set_option('optimization', 0)
  add_global_arguments('-g', language:'c')
endif

this try to avoid valac to add #line directives but make c to compile with debug so debug a vala complied code show the real c code.

but reading @jpakkane commens on other issues, I think meson cannot change options in meson.build files