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rust: procedural macros do not support LTO #15319

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c094151
compilers: pass target to get_lto_*_args
bonzini Nov 28, 2025
1883fbb
rust: Rust-ABI dynamic libraries do not support LTO
bonzini Nov 28, 2025
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9 changes: 6 additions & 3 deletions mesonbuild/compilers/compilers.py
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Original file line number Diff line number Diff line change
Expand Up @@ -279,6 +279,7 @@ def get_base_compile_args(target: 'BuildTarget', compiler: 'Compiler', env: 'Env
num_threads = get_option_value_for_target(env, target, OptionKey('b_lto_threads'), 0)
ltomode = get_option_value_for_target(env, target, OptionKey('b_lto_mode'), 'default')
args.extend(compiler.get_lto_compile_args(
target=target,
threads=num_threads,
mode=ltomode))
lto = True
Expand Down Expand Up @@ -357,6 +358,7 @@ def get_base_link_args(target: 'BuildTarget',
num_threads = get_option_value_for_target(env, target, OptionKey('b_lto_threads'), 0)
lto_mode = get_option_value_for_target(env, target, OptionKey('b_lto_mode'), 'default')
args.extend(linker.get_lto_link_args(
target=target,
threads=num_threads,
mode=lto_mode,
thinlto_cache_dir=thinlto_cache_dir))
Expand Down Expand Up @@ -1043,11 +1045,12 @@ def remove_linkerlike_args(self, args: T.List[str]) -> T.List[str]:
def get_embed_bitcode_args(self, bitcode: bool, lto: bool) -> T.List[str]:
return []

def get_lto_compile_args(self, *, threads: int = 0, mode: str = 'default') -> T.List[str]:
def get_lto_compile_args(self, *, target: T.Optional[BuildTarget] = None, threads: int = 0,
mode: str = 'default') -> T.List[str]:
return []

def get_lto_link_args(self, *, threads: int = 0, mode: str = 'default',
thinlto_cache_dir: T.Optional[str] = None) -> T.List[str]:
def get_lto_link_args(self, *, target: T.Optional[BuildTarget] = None, threads: int = 0,
mode: str = 'default', thinlto_cache_dir: T.Optional[str] = None) -> T.List[str]:
return self.linker.get_lto_args()

def get_lto_obj_cache_path(self, path: str) -> T.List[str]:
Expand Down
12 changes: 7 additions & 5 deletions mesonbuild/compilers/mixins/clang.py
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@
if T.TYPE_CHECKING:
from ...options import MutableKeyedOptionDictType
from ...dependencies import Dependency # noqa: F401
from ...build import BuildTarget
from ..compilers import Compiler

CompilerMixinBase = Compiler
Expand Down Expand Up @@ -211,7 +212,8 @@ def get_coverage_link_args(self) -> T.List[str]:
def get_embed_bitcode_args(self, bitcode: bool, lto: bool) -> T.List[str]:
return ['-fembed-bitcode'] if bitcode else []

def get_lto_compile_args(self, *, threads: int = 0, mode: str = 'default') -> T.List[str]:
def get_lto_compile_args(self, *, target: T.Optional[BuildTarget] = None, threads: int = 0,
mode: str = 'default') -> T.List[str]:
args: T.List[str] = []
if mode == 'thin':
# ThinLTO requires the use of gold, lld, ld64, lld-link or mold 1.1+
Expand All @@ -224,7 +226,7 @@ def get_lto_compile_args(self, *, threads: int = 0, mode: str = 'default') -> T.
args.append(f'-flto={mode}')
else:
assert mode == 'default', 'someone forgot to wire something up'
args.extend(super().get_lto_compile_args(threads=threads))
args.extend(super().get_lto_compile_args(target=target, threads=threads))
return args

def linker_to_compiler_args(self, args: T.List[str]) -> T.List[str]:
Expand All @@ -233,9 +235,9 @@ def linker_to_compiler_args(self, args: T.List[str]) -> T.List[str]:
else:
return args

def get_lto_link_args(self, *, threads: int = 0, mode: str = 'default',
thinlto_cache_dir: T.Optional[str] = None) -> T.List[str]:
args = self.get_lto_compile_args(threads=threads, mode=mode)
def get_lto_link_args(self, *, target: T.Optional[BuildTarget] = None, threads: int = 0,
mode: str = 'default', thinlto_cache_dir: T.Optional[str] = None) -> T.List[str]:
args = self.get_lto_compile_args(target=target, threads=threads, mode=mode)
if mode == 'thin' and thinlto_cache_dir is not None:
# We check for ThinLTO linker support above in get_lto_compile_args, and all of them support
# get_thinlto_cache_args as well
Expand Down
15 changes: 8 additions & 7 deletions mesonbuild/compilers/mixins/gnu.py
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Original file line number Diff line number Diff line change
Expand Up @@ -481,7 +481,8 @@ def get_compiler_dirs(self, name: str) -> T.List[str]:
return self._split_fetch_real_dirs(line.split('=', 1)[1])
return []

def get_lto_compile_args(self, *, threads: int = 0, mode: str = 'default') -> T.List[str]:
def get_lto_compile_args(self, *, target: T.Optional[BuildTarget] = None, threads: int = 0,
mode: str = 'default') -> T.List[str]:
# This provides a base for many compilers, GCC and Clang override this
# for their specific arguments
return ['-flto']
Expand Down Expand Up @@ -612,8 +613,8 @@ def get_has_func_attribute_extra_args(self, name: str) -> T.List[str]:
def get_prelink_args(self, prelink_name: str, obj_list: T.List[str]) -> T.Tuple[T.List[str], T.List[str]]:
return [prelink_name], ['-r', '-o', prelink_name] + obj_list

def get_lto_compile_args(self, *, threads: int = 0, mode: str = 'default',
thinlto_cache_dir: T.Optional[str] = None) -> T.List[str]:
def get_lto_compile_args(self, *, target: T.Optional[BuildTarget] = None, threads: int = 0,
mode: str = 'default', thinlto_cache_dir: T.Optional[str] = None) -> T.List[str]:
args: T.List[str] = []

if threads == 0:
Expand All @@ -626,7 +627,7 @@ def get_lto_compile_args(self, *, threads: int = 0, mode: str = 'default',
elif threads > 0:
args.append(f'-flto={threads}')
else:
args.extend(super().get_lto_compile_args(threads=threads))
args.extend(super().get_lto_compile_args(target=target, threads=threads))

if thinlto_cache_dir is not None:
# We check for ThinLTO linker support above in get_lto_compile_args, and all of them support
Expand All @@ -646,10 +647,10 @@ def use_linker_args(cls, linker: str, version: str) -> T.List[str]:
return ['-fuse-ld=mold']
return super().use_linker_args(linker, version)

def get_lto_link_args(self, *, threads: int = 0, mode: str = 'default',
thinlto_cache_dir: T.Optional[str] = None) -> T.List[str]:
def get_lto_link_args(self, *, target: T.Optional[BuildTarget] = None, threads: int = 0,
mode: str = 'default', thinlto_cache_dir: T.Optional[str] = None) -> T.List[str]:
args: T.List[str] = []
args.extend(self.get_lto_compile_args(threads=threads, thinlto_cache_dir=thinlto_cache_dir))
args.extend(self.get_lto_compile_args(target=target, threads=threads, thinlto_cache_dir=thinlto_cache_dir))
return args

def get_profile_use_args(self) -> T.List[str]:
Expand Down
4 changes: 2 additions & 2 deletions mesonbuild/compilers/mixins/islinker.py
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Original file line number Diff line number Diff line change
Expand Up @@ -40,8 +40,8 @@ class BasicLinkerIsCompilerMixin(Compiler):
def sanitizer_link_args(self, target: BuildTarget, value: T.List[str]) -> T.List[str]:
return []

def get_lto_link_args(self, *, threads: int = 0, mode: str = 'default',
thinlto_cache_dir: T.Optional[str] = None) -> T.List[str]:
def get_lto_link_args(self, *, target: T.Optional[BuildTarget] = None, threads: int = 0,
mode: str = 'default', thinlto_cache_dir: T.Optional[str] = None) -> T.List[str]:
return []

def can_linker_accept_rsp(self) -> bool:
Expand Down
9 changes: 5 additions & 4 deletions mesonbuild/compilers/mixins/visualstudio.py
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Expand Up @@ -492,7 +492,8 @@ def openmp_link_flags(self) -> T.List[str]:
raise mesonlib.MesonBugException('Could not find libomp')
return super().openmp_link_flags() + libs

def get_lto_compile_args(self, *, threads: int = 0, mode: str = 'default') -> T.List[str]:
def get_lto_compile_args(self, *, target: T.Optional[BuildTarget] = None, threads: int = 0,
mode: str = 'default') -> T.List[str]:
args: T.List[str] = []
if mode == 'thin':
# LTO data generated by clang-cl is only usable by lld-link
Expand All @@ -501,11 +502,11 @@ def get_lto_compile_args(self, *, threads: int = 0, mode: str = 'default') -> T.
args.append(f'-flto={mode}')
else:
assert mode == 'default', 'someone forgot to wire something up'
args.extend(super().get_lto_compile_args(threads=threads))
args.extend(super().get_lto_compile_args(target=target, threads=threads))
return args

def get_lto_link_args(self, *, threads: int = 0, mode: str = 'default',
thinlto_cache_dir: T.Optional[str] = None) -> T.List[str]:
def get_lto_link_args(self, *, target: T.Optional[BuildTarget] = None, threads: int = 0,
mode: str = 'default', thinlto_cache_dir: T.Optional[str] = None) -> T.List[str]:
args = []
if mode == 'thin' and thinlto_cache_dir is not None:
args.extend(self.linker.get_thinlto_cache_args(thinlto_cache_dir))
Expand Down
10 changes: 7 additions & 3 deletions mesonbuild/compilers/rust.py
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Original file line number Diff line number Diff line change
Expand Up @@ -365,13 +365,17 @@ def get_embed_bitcode_args(self, bitcode: bool, lto: bool) -> T.List[str]:
else:
return ['-C', 'embed-bitcode=no']

def get_lto_compile_args(self, *, threads: int = 0, mode: str = 'default') -> T.List[str]:
def get_lto_compile_args(self, *, target: T.Optional[BuildTarget] = None, threads: int = 0,
mode: str = 'default') -> T.List[str]:
if target.rust_crate_type in {'dylib', 'proc-macro'}:
return []

# TODO: what about -Clinker-plugin-lto?
rustc_lto = 'lto=thin' if mode == 'thin' else 'lto'
return ['-C', rustc_lto]

def get_lto_link_args(self, *, threads: int = 0, mode: str = 'default',
thinlto_cache_dir: T.Optional[str] = None) -> T.List[str]:
def get_lto_link_args(self, *, target: T.Optional[BuildTarget] = None, threads: int = 0,
mode: str = 'default', thinlto_cache_dir: T.Optional[str] = None) -> T.List[str]:
# no need to specify anything because the rustc command line
# includes the result of get_lto_compile_args()
return []
Expand Down
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