Handling Meson build options with multiple buildtypes

Question

Having read the Meson site pages (which are generally high quality), I'm still unsure about the intended best practice to handle different options for different buildtypes.

So to specify a debug build:

meson [srcdir] --buildtype=debug

Or to specify a release build:

meson [srcdir] --buildtype=release

However, if I want to add b_sanitize=address (or other arbitrary complex set of arguments) only for debug builds and b_ndebug=true only for release builds, I would do:

meson [srcdir] --buildtype=debug -Db_sanitize=address ...
meson [srcdir] --buildtype=release -Db_ndebug=true ...

However, it's more of a pain to add a bunch of custom arguments on the command line, and to me it seems neater to put that in the meson.build file. So I know I can set some built in options thusly:

project('myproject', ['cpp'],
        default_options : ['cpp_std=c++14',
                           'b_ndebug=true'])

But they are unconditionally set.

So a condition would look something like this:

if get_option('buildtype').startswith('release')
    add_project_arguments('-DNDEBUG', language : ['cpp'])
endif

Which is one way to do it, however, it would seem the b_ndebug=true way would be preferred to add_project_arguments('-DNDEBUG'), because it is portable.

How would the portable-style build options be conditionally set within the Meson script?

Additionally, b_sanitize=address is set without any test whether the compiler supports it. I would prefer for it to check first if it is supported (because the library might be missing, for example):

if meson.get_compiler('cpp').has_link_argument('-fsanitize=address')
    add_project_arguments('-fsanitize=address', language : ['cpp'])
    add_project_link_arguments('-fsanitize=address', language : ['cpp'])
endif

Is it possible to have the built-in portable-style build options (such as b_sanitize) have a check if they are supported?

Answer 1

I'm still unsure about the intended best practice to handle different options for different buildtypes

The intended best practice is to use meson configure to set/change the "buildtype" options as you need it. You don't have to do it "all at once and forever". But, of course, you can still have several distinct build trees (say, "debug" and "release") to speed up the process.

How would the portable-style build options be conditionally set within the Meson script?

Talking of b_ndebug, you can use the special value: ['b_ndebug=if-release'], which does exactly what you want. Also, you should take into account, that several GNU-style command-line arguments in meson are always portable, due to the internal compiler-specific substitutions. If I remember correctly, these include: -D, -I, -L and -l.

However, in general, changing "buildtype" options inside a script (except default_options, which are meant to be overwritten by meson setup/configure), is discouraged, and meson intentionally lacks set_option() function.

Is it possible to have the built-in portable-style build options (such as b_sanitize) have a check if they are supported?

AFAIK, no, except has_argument() you've used above. However, if some build option, like b_sanitize, is not supported by the underlying compiler, then it will be automatically set to void, so using it shouldn't break anything.