[mypyc] Refactor: Move compiler flag logic into a function (#20625)

Author: JukkaL

mypyc/build.py

@@ -545,6 +545,89 @@ def mypyc_build(
     return groups, group_cfilenames, source_deps
 
 
+def get_cflags(
+    *,
+    compiler_type: str | None = None,
+    opt_level: str = "3",
+    debug_level: str = "1",
+    multi_file: bool = False,
+    experimental_features: bool = False,
+    log_trace: bool = False,
+) -> list[str]:
+    """Get C compiler flags for the given configuration.
+
+    Args:
+        compiler_type: Compiler type, e.g. "unix" or "msvc". If None, detected automatically.
+        opt_level: Optimization level as string ("0", "1", "2", or "3").
+        debug_level: Debug level as string ("0", "1", "2", or "3").
+        multi_file: Whether multi-file compilation mode is enabled.
+        experimental_features: Whether experimental features are enabled.
+        log_trace: Whether trace logging is enabled.
+
+    Returns:
+        List of compiler flags.
+    """
+    if compiler_type is None:
+        compiler: Any = ccompiler.new_compiler()
+        sysconfig.customize_compiler(compiler)
+        compiler_type = compiler.compiler_type
+
+    cflags: list[str] = []
+    if compiler_type == "unix":
+        cflags += [
+            f"-O{opt_level}",
+            f"-g{debug_level}",
+            "-Werror",
+            "-Wno-unused-function",
+            "-Wno-unused-label",
+            "-Wno-unreachable-code",
+            "-Wno-unused-variable",
+            "-Wno-unused-command-line-argument",
+            "-Wno-unknown-warning-option",
+            "-Wno-unused-but-set-variable",
+            "-Wno-ignored-optimization-argument",
+            # Disables C Preprocessor (cpp) warnings
+            # See https://github.com/mypyc/mypyc/issues/956
+            "-Wno-cpp",
+        ]
+        if log_trace:
+            cflags.append("-DMYPYC_LOG_TRACE")
+        if experimental_features:
+            cflags.append("-DMYPYC_EXPERIMENTAL")
+        if opt_level == "0":
+            cflags.append("-UNDEBUG")
+    elif compiler_type == "msvc":
+        # msvc doesn't have levels, '/O2' is full and '/Od' is disable
+        if opt_level == "0":
+            opt_level = "d"
+            cflags.append("/UNDEBUG")
+        elif opt_level in ("1", "2", "3"):
+            opt_level = "2"
+        if debug_level == "0":
+            debug_level = "NONE"
+        elif debug_level == "1":
+            debug_level = "FASTLINK"
+        elif debug_level in ("2", "3"):
+            debug_level = "FULL"
+        cflags += [
+            f"/O{opt_level}",
+            f"/DEBUG:{debug_level}",
+            "/wd4102",  # unreferenced label
+            "/wd4101",  # unreferenced local variable
+            "/wd4146",  # negating unsigned int
+        ]
+        if multi_file:
+            # Disable whole program optimization in multi-file mode so
+            # that we actually get the compilation speed and memory
+            # use wins that multi-file mode is intended for.
+            cflags += ["/GL-", "/wd9025"]  # warning about overriding /GL
+        if log_trace:
+            cflags.append("/DMYPYC_LOG_TRACE")
+        if experimental_features:
+            cflags.append("/DMYPYC_EXPERIMENTAL")
+    return cflags
+
+
 def mypycify(
     paths: list[str],
     *,
@@ -659,59 +742,14 @@ def mypycify(
 
     build_dir = compiler_options.target_dir
 
-    cflags: list[str] = []
-    if compiler.compiler_type == "unix":
-        cflags += [
-            f"-O{opt_level}",
-            f"-g{debug_level}",
-            "-Werror",
-            "-Wno-unused-function",
-            "-Wno-unused-label",
-            "-Wno-unreachable-code",
-            "-Wno-unused-variable",
-            "-Wno-unused-command-line-argument",
-            "-Wno-unknown-warning-option",
-            "-Wno-unused-but-set-variable",
-            "-Wno-ignored-optimization-argument",
-            # Disables C Preprocessor (cpp) warnings
-            # See https://github.com/mypyc/mypyc/issues/956
-            "-Wno-cpp",
-        ]
-        if log_trace:
-            cflags.append("-DMYPYC_LOG_TRACE")
-        if experimental_features:
-            cflags.append("-DMYPYC_EXPERIMENTAL")
-        if opt_level == "0":
-            cflags.append("-UNDEBUG")
-    elif compiler.compiler_type == "msvc":
-        # msvc doesn't have levels, '/O2' is full and '/Od' is disable
-        if opt_level == "0":
-            opt_level = "d"
-            cflags.append("/UNDEBUG")
-        elif opt_level in ("1", "2", "3"):
-            opt_level = "2"
-        if debug_level == "0":
-            debug_level = "NONE"
-        elif debug_level == "1":
-            debug_level = "FASTLINK"
-        elif debug_level in ("2", "3"):
-            debug_level = "FULL"
-        cflags += [
-            f"/O{opt_level}",
-            f"/DEBUG:{debug_level}",
-            "/wd4102",  # unreferenced label
-            "/wd4101",  # unreferenced local variable
-            "/wd4146",  # negating unsigned int
-        ]
-        if multi_file:
-            # Disable whole program optimization in multi-file mode so
-            # that we actually get the compilation speed and memory
-            # use wins that multi-file mode is intended for.
-            cflags += ["/GL-", "/wd9025"]  # warning about overriding /GL
-        if log_trace:
-            cflags.append("/DMYPYC_LOG_TRACE")
-        if experimental_features:
-            cflags.append("/DMYPYC_EXPERIMENTAL")
+    cflags = get_cflags(
+        compiler_type=compiler.compiler_type,
+        opt_level=opt_level,
+        debug_level=debug_level,
+        multi_file=multi_file,
+        experimental_features=experimental_features,
+        log_trace=log_trace,
+    )
 
     # If configured to (defaults to yes in multi-file mode), copy the
     # runtime library in. Otherwise it just gets #included to save on