From c5a32c2afe843798d714fc9087bf55ad996b4052 Mon Sep 17 00:00:00 2001 From: Jon Turney Date: Sat, 8 Feb 2020 18:33:49 +0000 Subject: [PATCH] Refine behaviour of add_languages() when native: is missing This improves the common case of a simple meson.build which doesn't contain any 'native: true' targets to not require a native compiler when cross-compiling, without needing any changes in the meson.build. v2: Do it the right way around! --- docs/markdown/Reference-manual.md | 10 +++++++--- .../snippets/native_compiler_not_required.md | 19 +++++++++++++++++-- mesonbuild/interpreter.py | 4 ++-- 3 files changed, 26 insertions(+), 7 deletions(-) diff --git a/docs/markdown/Reference-manual.md b/docs/markdown/Reference-manual.md index 3b07b5f77..3e4cd44c4 100644 --- a/docs/markdown/Reference-manual.md +++ b/docs/markdown/Reference-manual.md @@ -75,12 +75,16 @@ specified is not found, Meson will halt. Since *0.47.0* the value of a [`feature`](Build-options.md#features) option can also be passed. - `native` if set to `true`, the language will be used to compile for the build - machine, if `false`, for the host machine. If omitted, the language may be - used for either. Since *0.54.0*. The default may change to `false` in a future - meson version. + machine, if `false`, for the host machine. Since *0.54.0*. Returns `true` if all languages specified were found and `false` otherwise. +If `native` is omitted, the languages may be used for either build or host +machine, but are never required for the build machine. (i.e. it is equivalent +to `add_languages(*langs*, native: false, required: *required*) and +add_languages(*langs*, native: true, required: false)`. This default behaviour +may change to `native: false` in a future meson version. + ### add_project_arguments() ``` meson diff --git a/docs/markdown/snippets/native_compiler_not_required.md b/docs/markdown/snippets/native_compiler_not_required.md index 0847b2bd7..331b3c759 100644 --- a/docs/markdown/snippets/native_compiler_not_required.md +++ b/docs/markdown/snippets/native_compiler_not_required.md @@ -1,5 +1,20 @@ ## Native (build machine) compilers not always required `add_languages()` gained a `native:` keyword, indicating if a native or cross -compiler is to be used. Currently, for backwards compatibility, if the keyword -is absent, that means both are used. +compiler is to be used. + +For the benefit of existing simple build definitions which don't contain any +`native: true` targets, without breaking backwards compatibility for build +definitions which assume that the native compiler is available after +`add_languages()`, if the `native:` keyword is absent the languages may be used +for either the build or host machine, but are never required for the build +machine. + +This changes the behaviour of the following meson fragment (when cross-compiling +but a native compiler is not available) from reporting an error at +`add_language` to reporting an error at `executable`. + +``` +add_language('c') +executable('main', 'main.c', native: true) +``` diff --git a/mesonbuild/interpreter.py b/mesonbuild/interpreter.py index 0d8347282..d7996966b 100644 --- a/mesonbuild/interpreter.py +++ b/mesonbuild/interpreter.py @@ -2927,9 +2927,9 @@ external dependencies (including libraries) must go to "dependencies".''') return self.add_languages(args, required, self.machine_from_native_kwarg(kwargs)) else: # absent 'native' means 'both' for backwards compatibility - mlog.warning('add_languages is missing native:, assuming languages are required for both host and build.', + mlog.warning('add_languages is missing native:, assuming languages are wanted for both host and build.', location=self.current_node) - success = self.add_languages(args, required, MachineChoice.BUILD) + success = self.add_languages(args, False, MachineChoice.BUILD) success &= self.add_languages(args, required, MachineChoice.HOST) return success