clang-tidy: Avoid spawning too many threads

The clang-tidy-fix target uses run-clang-tidy to do the fixing, however
this script itself spawns `os.cpu_count()` threads as part of its
internal parallelism. When combined with Meson's parallelism this
results in the creation of potentially thousands of unecessary threads.

This commit rewrites the clang-tidy-fix to perform the same task
run-clang-tidy does but exclusively on Meson's thread pool. "Fix-it"
snippets are saved to `meson-private/clang-tidy-fix/` by a parallel
clang-tidy phase, afterwards (to avoid races) all collected fixes are
applied with a single call to clang-apply-replacements.

1 files changed, 26 insertions, 0 deletions

diff --git a/mesonbuild/environment.py b/mesonbuild/environment.py
index 90c9bb911..71a2f3afc 100644
--- a/mesonbuild/environment.py
+++ b/mesonbuild/environment.py
@@ -275,6 +275,32 @@ def detect_clangformat() -> T.List[str]:
             return [path]
     return []
 
+def detect_clangtidy() -> T.List[str]:
+    """ Look for clang-tidy binary on build platform
+
+    Return: a single-element list of the found clang-tidy binary ready to be
+        passed to Popen()
+    """
+    tools = get_llvm_tool_names('clang-tidy')
+    for tool in tools:
+        path = shutil.which(tool)
+        if path is not None:
+            return [path]
+    return []
+
+def detect_clangapply() -> T.List[str]:
+    """ Look for clang-apply-replacements binary on build platform
+
+    Return: a single-element list of the found clang-apply-replacements binary
+        ready to be passed to Popen()
+    """
+    tools = get_llvm_tool_names('clang-apply-replacements')
+    for tool in tools:
+        path = shutil.which(tool)
+        if path is not None:
+            return [path]
+    return []
+
 def detect_windows_arch(compilers: CompilersDict) -> str:
     """
     Detecting the 'native' architecture of Windows is not a trivial task. We