compilers: Add optimization=plain option

https://github.com/mesonbuild/meson/pull/9287 changed the `optimization=0`
to pass `-O0` to the compiler. This change is reasonable by itself
but unfortunately, it breaks `buildtype=plain`, which promises
that “no extra build flags are used”.

`buildtype=plain` is important for distros like NixOS,
which manage compiler flags for optimization and hardening
themselves.

Let’s introduce a new optimization level that does nothing
and set it as the default for `buildtype=plain`.

13 files changed, 25 insertions, 7 deletions

diff --git a/mesonbuild/compilers/compilers.py b/mesonbuild/compilers/compilers.py
index 725d394..ea03869 100644
--- a/mesonbuild/compilers/compilers.py
+++ b/mesonbuild/compilers/compilers.py
@@ -254,7 +254,8 @@ msvc_winlibs = ['kernel32.lib', 'user32.lib', 'gdi32.lib',
                 'winspool.lib', 'shell32.lib', 'ole32.lib', 'oleaut32.lib',
                 'uuid.lib', 'comdlg32.lib', 'advapi32.lib']  # type: T.List[str]
 
-clike_optimization_args = {'0': [],
+clike_optimization_args = {'plain': [],
+                           '0': [],
                            'g': [],
                            '1': ['-O1'],
                            '2': ['-O2'],
@@ -262,7 +263,8 @@ clike_optimization_args = {'0': [],
                            's': ['-Os'],
                            }  # type: T.Dict[str, T.List[str]]
 
-cuda_optimization_args = {'0': [],
+cuda_optimization_args = {'plain': [],
+                          '0': [],
                           'g': ['-O0'],
                           '1': ['-O1'],
                           '2': ['-O2'],
diff --git a/mesonbuild/compilers/cs.py b/mesonbuild/compilers/cs.py
index 9690cdb..64cca96 100644
--- a/mesonbuild/compilers/cs.py
+++ b/mesonbuild/compilers/cs.py
@@ -28,7 +28,9 @@ if T.TYPE_CHECKING:
     from ..environment import Environment
     from ..mesonlib import MachineChoice
 
-cs_optimization_args = {'0': [],
+cs_optimization_args = {
+                        'plain': [],
+                        '0': [],
                         'g': [],
                         '1': ['-optimize+'],
                         '2': ['-optimize+'],
diff --git a/mesonbuild/compilers/d.py b/mesonbuild/compilers/d.py
index 54f0d9a..fbdf288 100644
--- a/mesonbuild/compilers/d.py
+++ b/mesonbuild/compilers/d.py
@@ -66,7 +66,8 @@ d_feature_args = {'gcc':  {'unittest': '-funittest',
                            }
                   }  # type: T.Dict[str, T.Dict[str, str]]
 
-ldc_optimization_args = {'0': [],
+ldc_optimization_args = {'plain': [],
+                         '0': [],
                          'g': [],
                          '1': ['-O1'],
                          '2': ['-O2'],
@@ -74,7 +75,8 @@ ldc_optimization_args = {'0': [],
                          's': ['-Oz'],
                          }  # type: T.Dict[str, T.List[str]]
 
-dmd_optimization_args = {'0': [],
+dmd_optimization_args = {'plain': [],
+                         '0': [],
                          'g': [],
                          '1': ['-O'],
                          '2': ['-O'],
diff --git a/mesonbuild/compilers/mixins/arm.py b/mesonbuild/compilers/mixins/arm.py
index 5bf862d..b3abd70 100644
--- a/mesonbuild/compilers/mixins/arm.py
+++ b/mesonbuild/compilers/mixins/arm.py
@@ -43,6 +43,7 @@ arm_buildtype_args = {
 }  # type: T.Dict[str, T.List[str]]
 
 arm_optimization_args = {
+    'plain': [],
     '0': ['-O0'],
     'g': ['-g'],
     '1': ['-O1'],
@@ -61,6 +62,7 @@ armclang_buildtype_args = {
 }  # type: T.Dict[str, T.List[str]]
 
 armclang_optimization_args = {
+    'plain': [],
     '0': [], # Compiler defaults to -O0
     'g': ['-g'],
     '1': ['-O1'],
diff --git a/mesonbuild/compilers/mixins/clang.py b/mesonbuild/compilers/mixins/clang.py
index 5083ace..4ac9b92 100644
--- a/mesonbuild/compilers/mixins/clang.py
+++ b/mesonbuild/compilers/mixins/clang.py
@@ -35,6 +35,7 @@ clang_color_args = {
 }  # type: T.Dict[str, T.List[str]]
 
 clang_optimization_args = {
+    'plain': [],
     '0': ['-O0'],
     'g': ['-Og'],
     '1': ['-O1'],
diff --git a/mesonbuild/compilers/mixins/compcert.py b/mesonbuild/compilers/mixins/compcert.py
index f1de8f1..f4f4cdb 100644
--- a/mesonbuild/compilers/mixins/compcert.py
+++ b/mesonbuild/compilers/mixins/compcert.py
@@ -40,6 +40,7 @@ ccomp_buildtype_args = {
 }  # type: T.Dict[str, T.List[str]]
 
 ccomp_optimization_args = {
+    'plain': [],
     '0': ['-O0'],
     'g': ['-O0'],
     '1': ['-O1'],
diff --git a/mesonbuild/compilers/mixins/gnu.py b/mesonbuild/compilers/mixins/gnu.py
index 1b1e8a1..11efcc9 100644
--- a/mesonbuild/compilers/mixins/gnu.py
+++ b/mesonbuild/compilers/mixins/gnu.py
@@ -55,6 +55,7 @@ gnulike_buildtype_args = {
 }  # type: T.Dict[str, T.List[str]]
 
 gnu_optimization_args = {
+    'plain': [],
     '0': ['-O0'],
     'g': ['-Og'],
     '1': ['-O1'],
diff --git a/mesonbuild/compilers/mixins/intel.py b/mesonbuild/compilers/mixins/intel.py
index 2698b39..9877a54 100644
--- a/mesonbuild/compilers/mixins/intel.py
+++ b/mesonbuild/compilers/mixins/intel.py
@@ -58,7 +58,8 @@ class IntelGnuLikeCompiler(GnuLikeCompiler):
         'custom': [],
     }  # type: T.Dict[str, T.List[str]]
 
-    OPTIM_ARGS = {
+    OPTIM_ARGS: T.Dict[str, T.List[str]] = {
+        'plain': [],
         '0': ['-O0'],
         'g': ['-O0'],
         '1': ['-O1'],
@@ -136,7 +137,8 @@ class IntelVisualStudioLikeCompiler(VisualStudioLikeCompiler):
         'custom': [],
     }  # type: T.Dict[str, T.List[str]]
 
-    OPTIM_ARGS = {
+    OPTIM_ARGS: T.Dict[str, T.List[str]] = {
+        'plain': [],
         '0': ['/Od'],
         'g': ['/Od'],
         '1': ['/O1'],
diff --git a/mesonbuild/compilers/mixins/ti.py b/mesonbuild/compilers/mixins/ti.py
index a98e6d0..1821b2a 100644
--- a/mesonbuild/compilers/mixins/ti.py
+++ b/mesonbuild/compilers/mixins/ti.py
@@ -41,6 +41,7 @@ ti_buildtype_args = {
 }  # type: T.Dict[str, T.List[str]]
 
 ti_optimization_args = {
+    'plain': [],
     '0': ['-O0'],
     'g': ['-Ooff'],
     '1': ['-O1'],
diff --git a/mesonbuild/compilers/mixins/visualstudio.py b/mesonbuild/compilers/mixins/visualstudio.py
index 81ecf74..dc5e962 100644
--- a/mesonbuild/compilers/mixins/visualstudio.py
+++ b/mesonbuild/compilers/mixins/visualstudio.py
@@ -62,6 +62,7 @@ vs64_instruction_set_args = {
 }  # T.Dicst[str, T.Optional[T.List[str]]]
 
 msvc_optimization_args = {
+    'plain': [],
     '0': ['/Od'],
     'g': [], # No specific flag to optimize debugging, /Zi or /ZI will create debug information
     '1': ['/O1'],
diff --git a/mesonbuild/compilers/mixins/xc16.py b/mesonbuild/compilers/mixins/xc16.py
index db7a337..f160b34 100644
--- a/mesonbuild/compilers/mixins/xc16.py
+++ b/mesonbuild/compilers/mixins/xc16.py
@@ -41,6 +41,7 @@ xc16_buildtype_args = {
 }  # type: T.Dict[str, T.List[str]]
 
 xc16_optimization_args = {
+    'plain': [],
     '0': ['-O0'],
     'g': ['-O0'],
     '1': ['-O1'],
diff --git a/mesonbuild/compilers/rust.py b/mesonbuild/compilers/rust.py
index a7bab0f..7456823 100644
--- a/mesonbuild/compilers/rust.py
+++ b/mesonbuild/compilers/rust.py
@@ -31,6 +31,7 @@ if T.TYPE_CHECKING:
 
 
 rust_optimization_args = {
+    'plain': [],
     '0': [],
     'g': ['-C', 'opt-level=0'],
     '1': ['-C', 'opt-level=1'],
diff --git a/mesonbuild/compilers/swift.py b/mesonbuild/compilers/swift.py
index 2e427f1..6d434ae 100644
--- a/mesonbuild/compilers/swift.py
+++ b/mesonbuild/compilers/swift.py
@@ -27,6 +27,7 @@ if T.TYPE_CHECKING:
     from ..mesonlib import MachineChoice
 
 swift_optimization_args = {
+    'plain': [],
     '0': [],
     'g': [],
     '1': ['-O'],