From 3a4af92a7359ff629a633f89f930981cb7909003 Mon Sep 17 00:00:00 2001
From: Jukka Lehtosalo <jukka.lehtosalo@iki.fi>
Date: Fri, 28 Nov 2025 13:36:40 +0000
Subject: [PATCH 1/6] Generalize primitive op dependencies to allow source file
 deps and multiple deps

---
 mypyc/analysis/capsule_deps.py        | 18 ++++++------
 mypyc/codegen/emitmodule.py           | 25 +++++++----------
 mypyc/ir/deps.py                      | 40 +++++++++++++++++++++++++++
 mypyc/ir/module_ir.py                 | 26 ++++++++++++++---
 mypyc/ir/ops.py                       | 17 ++++++------
 mypyc/irbuild/ll_builder.py           |  4 +--
 mypyc/primitives/librt_strings_ops.py | 11 ++++----
 mypyc/primitives/misc_ops.py          |  9 +++---
 mypyc/primitives/registry.py          | 25 +++++++++--------
 mypyc/transform/exceptions.py         |  1 +
 10 files changed, 118 insertions(+), 58 deletions(-)
 create mode 100644 mypyc/ir/deps.py

diff --git a/mypyc/analysis/capsule_deps.py b/mypyc/analysis/capsule_deps.py
index ada42ee03f289..e2e8563db7fe7 100644
--- a/mypyc/analysis/capsule_deps.py
+++ b/mypyc/analysis/capsule_deps.py
@@ -1,27 +1,29 @@
 from __future__ import annotations
 
+from mypyc.ir.deps import Dependency
 from mypyc.ir.func_ir import FuncIR
 from mypyc.ir.ops import CallC, PrimitiveOp
 
 
-def find_implicit_capsule_dependencies(fn: FuncIR) -> set[str] | None:
-    """Find implicit dependencies on capsules that need to be imported.
+def find_implicit_op_dependencies(fn: FuncIR) -> set[Dependency] | None:
+    """Find implicit dependencies that need to be imported.
 
     Using primitives or types defined in librt submodules such as "librt.base64"
-    requires a capsule import.
+    requires dependency imports (e.g., capsule imports).
 
     Note that a module can depend on a librt module even if it doesn't explicitly
     import it, for example via re-exported names or via return types of functions
     defined in other modules.
     """
-    deps: set[str] | None = None
+    deps: set[Dependency] | None = None
     for block in fn.blocks:
         for op in block.ops:
             # TODO: Also determine implicit type object dependencies (e.g. cast targets)
-            if isinstance(op, CallC) and op.capsule is not None:
-                if deps is None:
-                    deps = set()
-                deps.add(op.capsule)
+            if isinstance(op, CallC) and op.dependencies is not None:
+                for dep in op.dependencies:
+                    if deps is None:
+                        deps = set()
+                    deps.add(dep)
             else:
                 assert not isinstance(op, PrimitiveOp), "Lowered IR is expected"
     return deps
diff --git a/mypyc/codegen/emitmodule.py b/mypyc/codegen/emitmodule.py
index 959ad3a6d73d8..63d95e55536d6 100644
--- a/mypyc/codegen/emitmodule.py
+++ b/mypyc/codegen/emitmodule.py
@@ -27,15 +27,10 @@
 from mypy.options import Options
 from mypy.plugin import Plugin, ReportConfigContext
 from mypy.util import hash_digest, json_dumps
-from mypyc.analysis.capsule_deps import find_implicit_capsule_dependencies
+from mypyc.analysis.capsule_deps import find_implicit_op_dependencies
 from mypyc.codegen.cstring import c_string_initializer
-from mypyc.codegen.emit import (
-    Emitter,
-    EmitterContext,
-    HeaderDeclaration,
-    c_array_initializer,
-    native_function_doc_initializer,
-)
+from mypyc.ir.deps import LIBRT_BASE64, LIBRT_STRINGS
+from mypyc.codegen.emit import Emitter, EmitterContext, HeaderDeclaration, c_array_initializer, native_function_doc_initializer
 from mypyc.codegen.emitclass import generate_class, generate_class_reuse, generate_class_type_decl
 from mypyc.codegen.emitfunc import generate_native_function, native_function_header
 from mypyc.codegen.emitwrapper import (
@@ -263,9 +258,9 @@ def compile_scc_to_ir(
             # Switch to lower abstraction level IR.
             lower_ir(fn, compiler_options)
             # Calculate implicit module dependencies (needed for librt)
-            capsules = find_implicit_capsule_dependencies(fn)
-            if capsules is not None:
-                module.capsules.update(capsules)
+            deps = find_implicit_op_dependencies(fn)
+            if deps is not None:
+                module.dependencies.update(deps)
             # Perform optimizations.
             do_copy_propagation(fn, compiler_options)
             do_flag_elimination(fn, compiler_options)
@@ -611,9 +606,9 @@ def generate_c_for_modules(self) -> list[tuple[str, str]]:
         ext_declarations.emit_line("#include <CPy.h>")
         if self.compiler_options.depends_on_librt_internal:
             ext_declarations.emit_line("#include <librt_internal.h>")
-        if any("librt.base64" in mod.capsules for mod in self.modules.values()):
+        if any(LIBRT_BASE64 in mod.dependencies for mod in self.modules.values()):
             ext_declarations.emit_line("#include <librt_base64.h>")
-        if any("librt.strings" in mod.capsules for mod in self.modules.values()):
+        if any(LIBRT_STRINGS in mod.dependencies for mod in self.modules.values()):
             ext_declarations.emit_line("#include <librt_strings.h>")
 
         declarations = Emitter(self.context)
@@ -1072,11 +1067,11 @@ def emit_module_exec_func(
             emitter.emit_line("if (import_librt_internal() < 0) {")
             emitter.emit_line("return -1;")
             emitter.emit_line("}")
-        if "librt.base64" in module.capsules:
+        if LIBRT_BASE64 in module.dependencies:
             emitter.emit_line("if (import_librt_base64() < 0) {")
             emitter.emit_line("return -1;")
             emitter.emit_line("}")
-        if "librt.strings" in module.capsules:
+        if LIBRT_STRINGS in module.dependencies:
             emitter.emit_line("if (import_librt_strings() < 0) {")
             emitter.emit_line("return -1;")
             emitter.emit_line("}")
diff --git a/mypyc/ir/deps.py b/mypyc/ir/deps.py
new file mode 100644
index 0000000000000..4fa11f1d40e57
--- /dev/null
+++ b/mypyc/ir/deps.py
@@ -0,0 +1,40 @@
+from typing import Final, Union
+
+
+class Capsule:
+    """Defines a C extension capsule that a primitive may require."""
+
+    def __init__(self, name: str) -> None:
+        self.name: Final = name
+
+    def __repr__(self) -> str:
+        return f"Capsule(name={self.name!r})"
+
+    def __eq__(self, other: object) -> bool:
+        return isinstance(other, Capsule) and self.name == other.name
+
+    def __hash__(self) -> int:
+        return hash(("Capsule", self.name))
+
+
+class SourceDep:
+    """Defines a C source file that a primitive may require."""
+
+    def __init__(self, path: str) -> None:
+        self.path: Final = path
+
+    def __repr__(self) -> str:
+        return f"SourceDep(path={self.path!r})"
+
+    def __eq__(self, other: object) -> bool:
+        return isinstance(other, SourceDep) and self.path == other.path
+
+    def __hash__(self) -> int:
+        return hash(("SourceDep", self.path))
+
+
+Dependency = Union[Capsule, SourceDep]
+
+
+LIBRT_STRINGS: Final = Capsule("librt.strings")
+LIBRT_BASE64: Final = Capsule("librt.base64")
diff --git a/mypyc/ir/module_ir.py b/mypyc/ir/module_ir.py
index 5aef414490f9e..e978bb35e7ab0 100644
--- a/mypyc/ir/module_ir.py
+++ b/mypyc/ir/module_ir.py
@@ -4,6 +4,7 @@
 
 from mypyc.common import JsonDict
 from mypyc.ir.class_ir import ClassIR
+from mypyc.ir.deps import Capsule, Dependency, SourceDep
 from mypyc.ir.func_ir import FuncDecl, FuncIR
 from mypyc.ir.ops import DeserMaps
 from mypyc.ir.rtypes import RType, deserialize_type
@@ -30,17 +31,25 @@ def __init__(
         # These are only visible in the module that defined them, so no need
         # to serialize.
         self.type_var_names = type_var_names
-        # Capsules needed by the module, specified via module names such as "librt.base64"
-        self.capsules: set[str] = set()
+        # Dependencies needed by the module (such as capsules or source files)
+        self.dependencies: set[Dependency] = set()
 
     def serialize(self) -> JsonDict:
+        # Serialize dependencies as a list of dicts with type information
+        serialized_deps = []
+        for dep in sorted(self.dependencies, key=lambda d: (type(d).__name__, str(d))):
+            if isinstance(dep, Capsule):
+                serialized_deps.append({"type": "Capsule", "name": dep.name})
+            elif isinstance(dep, SourceDep):
+                serialized_deps.append({"type": "SourceDep", "path": dep.path})
+
         return {
             "fullname": self.fullname,
             "imports": self.imports,
             "functions": [f.serialize() for f in self.functions],
             "classes": [c.serialize() for c in self.classes],
             "final_names": [(k, t.serialize()) for k, t in self.final_names],
-            "capsules": sorted(self.capsules),
+            "dependencies": serialized_deps,
         }
 
     @classmethod
@@ -53,7 +62,16 @@ def deserialize(cls, data: JsonDict, ctx: DeserMaps) -> ModuleIR:
             [(k, deserialize_type(t, ctx)) for k, t in data["final_names"]],
             [],
         )
-        module.capsules = set(data["capsules"])
+
+        # Deserialize dependencies
+        deps: set[Dependency] = set()
+        for dep_dict in data["dependencies"]:
+            if dep_dict["type"] == "Capsule":
+                deps.add(Capsule(dep_dict["name"]))
+            elif dep_dict["type"] == "SourceDep":
+                deps.add(SourceDep(dep_dict["path"]))
+        module.dependencies = deps
+
         return module
 
 
diff --git a/mypyc/ir/ops.py b/mypyc/ir/ops.py
index beb709adfbd07..f478156ac41ad 100644
--- a/mypyc/ir/ops.py
+++ b/mypyc/ir/ops.py
@@ -55,6 +55,7 @@ class to enable the new behavior. Sometimes adding a new abstract
     short_int_rprimitive,
     void_rtype,
 )
+from mypyc.ir.deps import Dependency
 
 if TYPE_CHECKING:
     from mypyc.codegen.literals import LiteralValue
@@ -710,7 +711,7 @@ def __init__(
         priority: int,
         is_pure: bool,
         experimental: bool,
-        capsule: str | None,
+        dependencies: list[Dependency] | None,
     ) -> None:
         # Each primitive much have a distinct name, but otherwise they are arbitrary.
         self.name: Final = name
@@ -736,9 +737,9 @@ def __init__(
         # Experimental primitives are not used unless mypyc experimental features are
         # explicitly enabled
         self.experimental = experimental
-        # Capsule that needs to imported and configured to call the primitive
-        # (name of the target module, e.g. "librt.base64").
-        self.capsule = capsule
+        # Dependencies for the primitive, such as a capsule that needs to imported
+        # and configured to call the primitive.
+        self.dependencies = dependencies
         # Native integer types such as u8 can cause ambiguity in primitive
         # matching, since these are assignable to plain int *and* vice versa.
         # If this flag is set, the primitive has native integer types and must
@@ -1252,7 +1253,7 @@ def __init__(
         *,
         is_pure: bool = False,
         returns_null: bool = False,
-        capsule: str | None = None,
+        dependencies: list[Dependency] | None = None,
     ) -> None:
         self.error_kind = error_kind
         super().__init__(line)
@@ -1270,9 +1271,9 @@ def __init__(
         # The function might return a null value that does not indicate
         # an error.
         self.returns_null = returns_null
-        # A capsule from this module must be imported and initialized before calling this
-        # function (used for C functions exported from librt). Example value: "librt.base64"
-        self.capsule = capsule
+        # Dependencies (such as capsules) that must be imported and initialized before
+        # calling this function (used for C functions exported from librt).
+        self.dependencies = dependencies
         if is_pure or returns_null:
             assert error_kind == ERR_NEVER
 
diff --git a/mypyc/irbuild/ll_builder.py b/mypyc/irbuild/ll_builder.py
index 0a9e2d230ca5f..dcb352679cf81 100644
--- a/mypyc/irbuild/ll_builder.py
+++ b/mypyc/irbuild/ll_builder.py
@@ -2075,7 +2075,7 @@ def call_c(
                 var_arg_idx,
                 is_pure=desc.is_pure,
                 returns_null=desc.returns_null,
-                capsule=desc.capsule,
+                dependencies=desc.dependencies,
             )
         )
         if desc.is_borrowed:
@@ -2160,7 +2160,7 @@ def primitive_op(
                 desc.priority,
                 is_pure=desc.is_pure,
                 returns_null=False,
-                capsule=desc.capsule,
+                dependencies=desc.dependencies,
             )
             return self.call_c(c_desc, args, line, result_type=result_type)
 
diff --git a/mypyc/primitives/librt_strings_ops.py b/mypyc/primitives/librt_strings_ops.py
index 23a4033dced40..786784d15f60d 100644
--- a/mypyc/primitives/librt_strings_ops.py
+++ b/mypyc/primitives/librt_strings_ops.py
@@ -1,5 +1,6 @@
 from typing import Final
 
+from mypyc.ir.deps import LIBRT_STRINGS
 from mypyc.ir.ops import ERR_MAGIC, ERR_NEVER
 from mypyc.ir.rtypes import (
     KNOWN_NATIVE_TYPES,
@@ -20,7 +21,7 @@
     c_function_name="LibRTStrings_BytesWriter_internal",
     error_kind=ERR_MAGIC,
     experimental=True,
-    capsule="librt.strings",
+    dependencies=[LIBRT_STRINGS],
 )
 
 method_op(
@@ -30,7 +31,7 @@
     c_function_name="LibRTStrings_BytesWriter_getvalue_internal",
     error_kind=ERR_MAGIC,
     experimental=True,
-    capsule="librt.strings",
+    dependencies=[LIBRT_STRINGS],
 )
 
 method_op(
@@ -40,7 +41,7 @@
     c_function_name="LibRTStrings_BytesWriter_write_internal",
     error_kind=ERR_MAGIC,
     experimental=True,
-    capsule="librt.strings",
+    dependencies=[LIBRT_STRINGS],
 )
 
 method_op(
@@ -50,7 +51,7 @@
     c_function_name="LibRTStrings_BytesWriter_append_internal",
     error_kind=ERR_MAGIC,
     experimental=True,
-    capsule="librt.strings",
+    dependencies=[LIBRT_STRINGS],
 )
 
 method_op(
@@ -68,5 +69,5 @@
     c_function_name="LibRTStrings_BytesWriter_len_internal",
     error_kind=ERR_NEVER,
     experimental=True,
-    capsule="librt.strings",
+    dependencies=[LIBRT_STRINGS],
 )
diff --git a/mypyc/primitives/misc_ops.py b/mypyc/primitives/misc_ops.py
index f6cb4fee97595..01853341b8bf9 100644
--- a/mypyc/primitives/misc_ops.py
+++ b/mypyc/primitives/misc_ops.py
@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+from mypyc.ir.deps import LIBRT_BASE64
 from mypyc.ir.ops import ERR_FALSE, ERR_MAGIC, ERR_MAGIC_OVERLAPPING, ERR_NEVER
 from mypyc.ir.rtypes import (
     KNOWN_NATIVE_TYPES,
@@ -475,7 +476,7 @@
     error_kind=ERR_MAGIC,
     extra_int_constants=[(0, bool_rprimitive)],
     experimental=True,
-    capsule="librt.base64",
+    dependencies=[LIBRT_BASE64],
 )
 
 function_op(
@@ -486,7 +487,7 @@
     error_kind=ERR_MAGIC,
     extra_int_constants=[(1, bool_rprimitive)],
     experimental=True,
-    capsule="librt.base64",
+    dependencies=[LIBRT_BASE64],
 )
 
 function_op(
@@ -497,7 +498,7 @@
     error_kind=ERR_MAGIC,
     extra_int_constants=[(0, bool_rprimitive)],
     experimental=True,
-    capsule="librt.base64",
+    dependencies=[LIBRT_BASE64],
 )
 
 function_op(
@@ -508,7 +509,7 @@
     error_kind=ERR_MAGIC,
     extra_int_constants=[(1, bool_rprimitive)],
     experimental=True,
-    capsule="librt.base64",
+    dependencies=[LIBRT_BASE64],
 )
 
 cpyfunction_get_name = function_op(
diff --git a/mypyc/primitives/registry.py b/mypyc/primitives/registry.py
index c7ab6925b43d3..650800462ac59 100644
--- a/mypyc/primitives/registry.py
+++ b/mypyc/primitives/registry.py
@@ -41,6 +41,7 @@
 
 from mypyc.ir.ops import PrimitiveDescription, StealsDescription
 from mypyc.ir.rtypes import RType
+from mypyc.ir.deps import Dependency
 
 # Error kind for functions that return negative integer on exception. This
 # is only used for primitives. We translate it away during IR building.
@@ -62,7 +63,7 @@ class CFunctionDescription(NamedTuple):
     priority: int
     is_pure: bool
     returns_null: bool
-    capsule: str | None
+    dependencies: list[Dependency] | None
 
 
 # A description for C load operations including LoadGlobal and LoadAddress
@@ -102,7 +103,7 @@ def method_op(
     priority: int = 1,
     is_pure: bool = False,
     experimental: bool = False,
-    capsule: str | None = None,
+    dependencies: list[Dependency] | None = None,
 ) -> PrimitiveDescription:
     """Define a c function call op that replaces a method call.
 
@@ -148,7 +149,7 @@ def method_op(
         priority,
         is_pure=is_pure,
         experimental=experimental,
-        capsule=capsule,
+        dependencies=dependencies,
     )
     ops.append(desc)
     return desc
@@ -168,7 +169,7 @@ def function_op(
     is_borrowed: bool = False,
     priority: int = 1,
     experimental: bool = False,
-    capsule: str | None = None,
+    dependencies: list[Dependency] | None = None,
 ) -> PrimitiveDescription:
     """Define a C function call op that replaces a function call.
 
@@ -198,7 +199,7 @@ def function_op(
         priority=priority,
         is_pure=False,
         experimental=experimental,
-        capsule=capsule,
+        dependencies=dependencies,
     )
     ops.append(desc)
     return desc
@@ -218,7 +219,7 @@ def binary_op(
     steals: StealsDescription = False,
     is_borrowed: bool = False,
     priority: int = 1,
-    capsule: str | None = None,
+    dependencies: list[Dependency] | None = None,
 ) -> PrimitiveDescription:
     """Define a c function call op for a binary operation.
 
@@ -247,7 +248,7 @@ def binary_op(
         priority=priority,
         is_pure=False,
         experimental=False,
-        capsule=capsule,
+        dependencies=dependencies,
     )
     ops.append(desc)
     return desc
@@ -289,7 +290,7 @@ def custom_op(
         0,
         is_pure=is_pure,
         returns_null=returns_null,
-        capsule=None,
+        dependencies=None,
     )
 
 
@@ -307,7 +308,7 @@ def custom_primitive_op(
     is_borrowed: bool = False,
     is_pure: bool = False,
     experimental: bool = False,
-    capsule: str | None = None,
+    dependencies: list[Dependency] | None = None,
 ) -> PrimitiveDescription:
     """Define a primitive op that can't be automatically generated based on the AST.
 
@@ -330,7 +331,7 @@ def custom_primitive_op(
         priority=0,
         is_pure=is_pure,
         experimental=experimental,
-        capsule=capsule,
+        dependencies=dependencies,
     )
 
 
@@ -347,7 +348,7 @@ def unary_op(
     is_borrowed: bool = False,
     priority: int = 1,
     is_pure: bool = False,
-    capsule: str | None = None,
+    dependencies: list[Dependency] | None = None,
 ) -> PrimitiveDescription:
     """Define a primitive op for an unary operation.
 
@@ -374,7 +375,7 @@ def unary_op(
         priority=priority,
         is_pure=is_pure,
         experimental=False,
-        capsule=capsule,
+        dependencies=dependencies,
     )
     ops.append(desc)
     return desc
diff --git a/mypyc/transform/exceptions.py b/mypyc/transform/exceptions.py
index 33dfeb693cf70..28bbd80c52cc2 100644
--- a/mypyc/transform/exceptions.py
+++ b/mypyc/transform/exceptions.py
@@ -146,6 +146,7 @@ def primitive_call(desc: CFunctionDescription, args: list[Value], line: int) ->
         desc.is_borrowed,
         desc.error_kind,
         line,
+        dependencies=desc.dependencies,
     )
 
 

From 1aa7dde9111808d0823f1b7888e29c79054c2d8d Mon Sep 17 00:00:00 2001
From: Jukka Lehtosalo <jukka.lehtosalo@iki.fi>
Date: Fri, 28 Nov 2025 14:26:17 +0000
Subject: [PATCH 2/6] Support extra source file deps and use bytes translate as
 an example

---
 mypyc/build.py                 | 43 +++++++++++++++++++++++------
 mypyc/codegen/emitmodule.py    | 20 ++++++++++++++
 mypyc/common.py                |  3 +-
 mypyc/ir/deps.py               |  6 ++++
 mypyc/lib-rt/CPy.h             |  1 -
 mypyc/lib-rt/bytes_extra_ops.c | 50 ++++++++++++++++++++++++++++++++++
 mypyc/lib-rt/bytes_extra_ops.h | 10 +++++++
 mypyc/lib-rt/bytes_ops.c       | 49 ---------------------------------
 mypyc/primitives/bytes_ops.py  |  2 ++
 9 files changed, 124 insertions(+), 60 deletions(-)
 create mode 100644 mypyc/lib-rt/bytes_extra_ops.c
 create mode 100644 mypyc/lib-rt/bytes_extra_ops.h

diff --git a/mypyc/build.py b/mypyc/build.py
index 9de5ccaabaaa8..45edeb07c93e5 100644
--- a/mypyc/build.py
+++ b/mypyc/build.py
@@ -39,6 +39,8 @@
 from mypyc.codegen import emitmodule
 from mypyc.common import IS_FREE_THREADED, RUNTIME_C_FILES, shared_lib_name
 from mypyc.errors import Errors
+from mypyc.ir.deps import SourceDep
+from mypyc.ir.module_ir import ModuleIR
 from mypyc.ir.pprint import format_modules
 from mypyc.namegen import exported_name
 from mypyc.options import CompilerOptions
@@ -276,20 +278,30 @@ def include_dir() -> str:
     return os.path.join(os.path.abspath(os.path.dirname(__file__)), "lib-rt")
 
 
+def collect_source_dependencies(modules: dict[str, ModuleIR]) -> set[SourceDep]:
+    """Collect all SourceDep dependencies from all modules."""
+    source_deps: set[SourceDep] = set()
+    for module in modules.values():
+        for dep in module.dependencies:
+            if isinstance(dep, SourceDep):
+                source_deps.add(dep)
+    return source_deps
+
+
 def generate_c(
     sources: list[BuildSource],
     options: Options,
     groups: emitmodule.Groups,
     fscache: FileSystemCache,
     compiler_options: CompilerOptions,
-) -> tuple[list[list[tuple[str, str]]], str]:
+) -> tuple[list[list[tuple[str, str]]], str, list[SourceDep]]:
     """Drive the actual core compilation step.
 
     The groups argument describes how modules are assigned to C
     extension modules. See the comments on the Groups type in
     mypyc.emitmodule for details.
 
-    Returns the C source code and (for debugging) the pretty printed IR.
+    Returns the C source code, (for debugging) the pretty printed IR, and list of SourceDeps.
     """
     t0 = time.time()
 
@@ -325,7 +337,10 @@ def generate_c(
     if options.mypyc_annotation_file:
         generate_annotated_html(options.mypyc_annotation_file, result, modules, mapper)
 
-    return ctext, "\n".join(format_modules(modules))
+    # Collect SourceDep dependencies
+    source_deps = sorted(collect_source_dependencies(modules), key=lambda d: d.path)
+
+    return ctext, "\n".join(format_modules(modules)), source_deps
 
 
 def build_using_shared_lib(
@@ -488,7 +503,7 @@ def mypyc_build(
     only_compile_paths: Iterable[str] | None = None,
     skip_cgen_input: Any | None = None,
     always_use_shared_lib: bool = False,
-) -> tuple[emitmodule.Groups, list[tuple[list[str], list[str]]]]:
+) -> tuple[emitmodule.Groups, list[tuple[list[str], list[str]]], list[SourceDep]]:
     """Do the front and middle end of mypyc building, producing and writing out C source."""
     fscache = FileSystemCache()
     mypyc_sources, all_sources, options = get_mypy_config(
@@ -511,8 +526,9 @@ def mypyc_build(
 
     # We let the test harness just pass in the c file contents instead
     # so that it can do a corner-cutting version without full stubs.
+    source_deps: list[SourceDep] = []
     if not skip_cgen_input:
-        group_cfiles, ops_text = generate_c(
+        group_cfiles, ops_text, source_deps = generate_c(
             all_sources, options, groups, fscache, compiler_options=compiler_options
         )
         # TODO: unique names?
@@ -535,7 +551,7 @@ def mypyc_build(
         deps = [os.path.join(compiler_options.target_dir, dep) for dep in get_header_deps(cfiles)]
         group_cfilenames.append((cfilenames, deps))
 
-    return groups, group_cfilenames
+    return groups, group_cfilenames, source_deps
 
 
 def mypycify(
@@ -633,7 +649,7 @@ def mypycify(
     )
 
     # Generate all the actual important C code
-    groups, group_cfilenames = mypyc_build(
+    groups, group_cfilenames, source_deps = mypyc_build(
         paths,
         only_compile_paths=only_compile_paths,
         compiler_options=compiler_options,
@@ -708,11 +724,20 @@ def mypycify(
     # compiler invocations.
     shared_cfilenames = []
     if not compiler_options.include_runtime_files:
-        for name in RUNTIME_C_FILES:
+        # Collect all files to copy: runtime files + conditional source files
+        files_to_copy = list(RUNTIME_C_FILES)
+        for source_dep in source_deps:
+            files_to_copy.append(source_dep.path)
+            files_to_copy.append(source_dep.get_header())
+
+        # Copy all files
+        for name in files_to_copy:
             rt_file = os.path.join(build_dir, name)
             with open(os.path.join(include_dir(), name), encoding="utf-8") as f:
                 write_file(rt_file, f.read())
-            shared_cfilenames.append(rt_file)
+            # Only add .c files to shared_cfilenames
+            if name.endswith('.c'):
+                shared_cfilenames.append(rt_file)
 
     extensions = []
     for (group_sources, lib_name), (cfilenames, deps) in zip(groups, group_cfilenames):
diff --git a/mypyc/codegen/emitmodule.py b/mypyc/codegen/emitmodule.py
index 63d95e55536d6..61880740028f7 100644
--- a/mypyc/codegen/emitmodule.py
+++ b/mypyc/codegen/emitmodule.py
@@ -422,6 +422,18 @@ def load_scc_from_cache(
     return modules
 
 
+def collect_source_dependencies(modules: dict[str, ModuleIR]) -> set[SourceDep]:
+    """Collect all SourceDep dependencies from all modules."""
+    from mypyc.ir.deps import SourceDep
+
+    source_deps: set[SourceDep] = set()
+    for module in modules.values():
+        for dep in module.dependencies:
+            if isinstance(dep, SourceDep):
+                source_deps.add(dep)
+    return source_deps
+
+
 def compile_modules_to_c(
     result: BuildResult, compiler_options: CompilerOptions, errors: Errors, groups: Groups
 ) -> tuple[ModuleIRs, list[FileContents], Mapper]:
@@ -555,6 +567,10 @@ def generate_c_for_modules(self) -> list[tuple[str, str]]:
         if self.compiler_options.include_runtime_files:
             for name in RUNTIME_C_FILES:
                 base_emitter.emit_line(f'#include "{name}"')
+            # Include conditional source files
+            source_deps = collect_source_dependencies(self.modules)
+            for source_dep in sorted(source_deps, key=lambda d: d.path):
+                base_emitter.emit_line(f'#include "{source_dep.path}"')
         base_emitter.emit_line(f'#include "__native{self.short_group_suffix}.h"')
         base_emitter.emit_line(f'#include "__native_internal{self.short_group_suffix}.h"')
         emitter = base_emitter
@@ -610,6 +626,10 @@ def generate_c_for_modules(self) -> list[tuple[str, str]]:
             ext_declarations.emit_line("#include <librt_base64.h>")
         if any(LIBRT_STRINGS in mod.dependencies for mod in self.modules.values()):
             ext_declarations.emit_line("#include <librt_strings.h>")
+        # Include headers for conditional source files
+        source_deps = collect_source_dependencies(self.modules)
+        for source_dep in sorted(source_deps, key=lambda d: d.path):
+            ext_declarations.emit_line(f'#include "{source_dep.get_header()}"')
 
         declarations = Emitter(self.context)
         declarations.emit_line(f"#ifndef MYPYC_LIBRT_INTERNAL{self.group_suffix}_H")
diff --git a/mypyc/common.py b/mypyc/common.py
index 28b386f450a63..4ee004c0dd0f6 100644
--- a/mypyc/common.py
+++ b/mypyc/common.py
@@ -65,7 +65,8 @@
 BITMAP_TYPE: Final = "uint32_t"
 BITMAP_BITS: Final = 32
 
-# Runtime C library files
+# Runtime C library files that are always included (some ops may bring
+# extra dependencies via mypyc.ir.SourceDep)
 RUNTIME_C_FILES: Final = [
     "init.c",
     "getargs.c",
diff --git a/mypyc/ir/deps.py b/mypyc/ir/deps.py
index 4fa11f1d40e57..01fd060d48197 100644
--- a/mypyc/ir/deps.py
+++ b/mypyc/ir/deps.py
@@ -32,9 +32,15 @@ def __eq__(self, other: object) -> bool:
     def __hash__(self) -> int:
         return hash(("SourceDep", self.path))
 
+    def get_header(self) -> str:
+        """Get the header file path by replacing .c with .h"""
+        return self.path.replace('.c', '.h')
+
 
 Dependency = Union[Capsule, SourceDep]
 
 
 LIBRT_STRINGS: Final = Capsule("librt.strings")
 LIBRT_BASE64: Final = Capsule("librt.base64")
+
+BYTES_EXTRA_OPS: Final = SourceDep("bytes_extra_ops.c")
diff --git a/mypyc/lib-rt/CPy.h b/mypyc/lib-rt/CPy.h
index 15995db3dfd0d..5526508f5acaa 100644
--- a/mypyc/lib-rt/CPy.h
+++ b/mypyc/lib-rt/CPy.h
@@ -783,7 +783,6 @@ PyObject *CPyBytes_Concat(PyObject *a, PyObject *b);
 PyObject *CPyBytes_Join(PyObject *sep, PyObject *iter);
 CPyTagged CPyBytes_Ord(PyObject *obj);
 PyObject *CPyBytes_Multiply(PyObject *bytes, CPyTagged count);
-PyObject *CPyBytes_Translate(PyObject *bytes, PyObject *table);
 
 
 int CPyBytes_Compare(PyObject *left, PyObject *right);
diff --git a/mypyc/lib-rt/bytes_extra_ops.c b/mypyc/lib-rt/bytes_extra_ops.c
new file mode 100644
index 0000000000000..b5d2d9996d52d
--- /dev/null
+++ b/mypyc/lib-rt/bytes_extra_ops.c
@@ -0,0 +1,50 @@
+#include "bytes_extra_ops.h"
+
+PyObject *CPyBytes_Translate(PyObject *bytes, PyObject *table) {
+    // Fast path: exact bytes object with exact bytes table
+    if (PyBytes_CheckExact(bytes) && PyBytes_CheckExact(table)) {
+        Py_ssize_t table_len = PyBytes_GET_SIZE(table);
+        if (table_len != 256) {
+            PyErr_SetString(PyExc_ValueError,
+                           "translation table must be 256 characters long");
+            return NULL;
+        }
+
+        Py_ssize_t len = PyBytes_GET_SIZE(bytes);
+        const char *input = PyBytes_AS_STRING(bytes);
+        const char *trans_table = PyBytes_AS_STRING(table);
+
+        PyObject *result = PyBytes_FromStringAndSize(NULL, len);
+        if (result == NULL) {
+            return NULL;
+        }
+
+        char *output = PyBytes_AS_STRING(result);
+        bool changed = false;
+
+        // Without a loop unrolling hint performance can be worse than CPython
+        CPY_UNROLL_LOOP(4)
+        for (Py_ssize_t i = len; --i >= 0;) {
+            char c = *input++;
+            if ((*output++ = trans_table[(unsigned char)c]) != c)
+                changed = true;
+        }
+
+        // If nothing changed, discard result and return the original object
+        if (!changed) {
+            Py_DECREF(result);
+            Py_INCREF(bytes);
+            return bytes;
+        }
+
+        return result;
+    }
+
+    // Fallback to Python method call for non-exact types or non-standard tables
+    _Py_IDENTIFIER(translate);
+    PyObject *name = _PyUnicode_FromId(&PyId_translate);
+    if (name == NULL) {
+        return NULL;
+    }
+    return PyObject_CallMethodOneArg(bytes, name, table);
+}
diff --git a/mypyc/lib-rt/bytes_extra_ops.h b/mypyc/lib-rt/bytes_extra_ops.h
new file mode 100644
index 0000000000000..eebb5a3454388
--- /dev/null
+++ b/mypyc/lib-rt/bytes_extra_ops.h
@@ -0,0 +1,10 @@
+#ifndef MYPYC_BYTES_EXTRA_OPS_H
+#define MYPYC_BYTES_EXTRA_OPS_H
+
+#include <Python.h>
+#include "CPy.h"
+
+// Optimized bytes translate operation
+PyObject *CPyBytes_Translate(PyObject *bytes, PyObject *table);
+
+#endif
diff --git a/mypyc/lib-rt/bytes_ops.c b/mypyc/lib-rt/bytes_ops.c
index 6c138ad90db0d..8ecf9337c28b8 100644
--- a/mypyc/lib-rt/bytes_ops.c
+++ b/mypyc/lib-rt/bytes_ops.c
@@ -171,52 +171,3 @@ PyObject *CPyBytes_Multiply(PyObject *bytes, CPyTagged count) {
     }
     return PySequence_Repeat(bytes, temp_count);
 }
-
-PyObject *CPyBytes_Translate(PyObject *bytes, PyObject *table) {
-    // Fast path: exact bytes object with exact bytes table
-    if (PyBytes_CheckExact(bytes) && PyBytes_CheckExact(table)) {
-        Py_ssize_t table_len = PyBytes_GET_SIZE(table);
-        if (table_len != 256) {
-            PyErr_SetString(PyExc_ValueError,
-                           "translation table must be 256 characters long");
-            return NULL;
-        }
-
-        Py_ssize_t len = PyBytes_GET_SIZE(bytes);
-        const char *input = PyBytes_AS_STRING(bytes);
-        const char *trans_table = PyBytes_AS_STRING(table);
-
-        PyObject *result = PyBytes_FromStringAndSize(NULL, len);
-        if (result == NULL) {
-            return NULL;
-        }
-
-        char *output = PyBytes_AS_STRING(result);
-        bool changed = false;
-
-        // Without a loop unrolling hint performance can be worse than CPython
-        CPY_UNROLL_LOOP(4)
-        for (Py_ssize_t i = len; --i >= 0;) {
-            char c = *input++;
-            if ((*output++ = trans_table[(unsigned char)c]) != c)
-                changed = true;
-        }
-
-        // If nothing changed, discard result and return the original object
-        if (!changed) {
-            Py_DECREF(result);
-            Py_INCREF(bytes);
-            return bytes;
-        }
-
-        return result;
-    }
-
-    // Fallback to Python method call for non-exact types or non-standard tables
-    _Py_IDENTIFIER(translate);
-    PyObject *name = _PyUnicode_FromId(&PyId_translate);
-    if (name == NULL) {
-        return NULL;
-    }
-    return PyObject_CallMethodOneArg(bytes, name, table);
-}
diff --git a/mypyc/primitives/bytes_ops.py b/mypyc/primitives/bytes_ops.py
index 982c41dc25b10..0669ddac00df3 100644
--- a/mypyc/primitives/bytes_ops.py
+++ b/mypyc/primitives/bytes_ops.py
@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+from mypyc.ir.deps import BYTES_EXTRA_OPS
 from mypyc.ir.ops import ERR_MAGIC, ERR_NEVER
 from mypyc.ir.rtypes import (
     RUnion,
@@ -135,6 +136,7 @@
     return_type=bytes_rprimitive,
     c_function_name="CPyBytes_Translate",
     error_kind=ERR_MAGIC,
+    dependencies=[BYTES_EXTRA_OPS],
 )
 
 # Join bytes objects and return a new bytes.

From 8907b8727698e567b6fa256e69452f864e070f58 Mon Sep 17 00:00:00 2001
From: Jukka Lehtosalo <jukka.lehtosalo@iki.fi>
Date: Fri, 28 Nov 2025 14:34:21 +0000
Subject: [PATCH 3/6] Fix header test

---
 mypyc/test/test_cheader.py | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/mypyc/test/test_cheader.py b/mypyc/test/test_cheader.py
index ec9e2c4cf4504..dc975b2b9d418 100644
--- a/mypyc/test/test_cheader.py
+++ b/mypyc/test/test_cheader.py
@@ -8,6 +8,7 @@
 import unittest
 
 from mypyc.primitives import registry
+from mypyc.ir.deps import SourceDep
 
 
 class TestHeaderInclusion(unittest.TestCase):
@@ -24,6 +25,7 @@ def check_name(name: str) -> None:
                     rf"\b{name}\b", header
                 ), f'"{name}" is used in mypyc.primitives but not declared in CPy.h'
 
+        all_ops = []
         for values in [
             registry.method_call_ops.values(),
             registry.binary_ops.values(),
@@ -31,9 +33,21 @@ def check_name(name: str) -> None:
             registry.function_ops.values(),
         ]:
             for ops in values:
-                for op in ops:
-                    if op.c_function_name is not None:
-                        check_name(op.c_function_name)
+                all_ops.extend(ops)
+
+        # Find additional headers via extra C source file dependencies.
+        for op in all_ops:
+            if op.dependencies:
+                for dep in op.dependencies:
+                    if isinstance(dep, SourceDep):
+                        header_fnam = os.path.join(base_dir, dep.get_header())
+                        if os.path.isfile(header_fnam):
+                            with open(os.path.join(base_dir, header_fnam)) as f:
+                                header += f.read()
+
+        for op in all_ops:
+            if op.c_function_name is not None:
+                check_name(op.c_function_name)
 
         primitives_path = os.path.join(os.path.dirname(__file__), "..", "primitives")
         for fnam in glob.glob(f"{primitives_path}/*.py"):

From b7453d6178632ffa453734480a3dfc83a0cae1ed Mon Sep 17 00:00:00 2001
From: Jukka Lehtosalo <jukka.lehtosalo@iki.fi>
Date: Fri, 28 Nov 2025 14:45:16 +0000
Subject: [PATCH 4/6] Clean up

---
 mypyc/build.py               | 15 ++-------------
 mypyc/codegen/emitmodule.py  | 12 ++++++++----
 mypyc/ir/deps.py             |  6 +++---
 mypyc/ir/ops.py              |  2 +-
 mypyc/primitives/registry.py |  2 +-
 mypyc/test/test_cheader.py   |  2 +-
 6 files changed, 16 insertions(+), 23 deletions(-)

diff --git a/mypyc/build.py b/mypyc/build.py
index 45edeb07c93e5..198865dc787bb 100644
--- a/mypyc/build.py
+++ b/mypyc/build.py
@@ -40,7 +40,6 @@
 from mypyc.common import IS_FREE_THREADED, RUNTIME_C_FILES, shared_lib_name
 from mypyc.errors import Errors
 from mypyc.ir.deps import SourceDep
-from mypyc.ir.module_ir import ModuleIR
 from mypyc.ir.pprint import format_modules
 from mypyc.namegen import exported_name
 from mypyc.options import CompilerOptions
@@ -278,16 +277,6 @@ def include_dir() -> str:
     return os.path.join(os.path.abspath(os.path.dirname(__file__)), "lib-rt")
 
 
-def collect_source_dependencies(modules: dict[str, ModuleIR]) -> set[SourceDep]:
-    """Collect all SourceDep dependencies from all modules."""
-    source_deps: set[SourceDep] = set()
-    for module in modules.values():
-        for dep in module.dependencies:
-            if isinstance(dep, SourceDep):
-                source_deps.add(dep)
-    return source_deps
-
-
 def generate_c(
     sources: list[BuildSource],
     options: Options,
@@ -338,7 +327,7 @@ def generate_c(
         generate_annotated_html(options.mypyc_annotation_file, result, modules, mapper)
 
     # Collect SourceDep dependencies
-    source_deps = sorted(collect_source_dependencies(modules), key=lambda d: d.path)
+    source_deps = sorted(emitmodule.collect_source_dependencies(modules), key=lambda d: d.path)
 
     return ctext, "\n".join(format_modules(modules)), source_deps
 
@@ -736,7 +725,7 @@ def mypycify(
             with open(os.path.join(include_dir(), name), encoding="utf-8") as f:
                 write_file(rt_file, f.read())
             # Only add .c files to shared_cfilenames
-            if name.endswith('.c'):
+            if name.endswith(".c"):
                 shared_cfilenames.append(rt_file)
 
     extensions = []
diff --git a/mypyc/codegen/emitmodule.py b/mypyc/codegen/emitmodule.py
index 61880740028f7..a56083796e79d 100644
--- a/mypyc/codegen/emitmodule.py
+++ b/mypyc/codegen/emitmodule.py
@@ -29,8 +29,13 @@
 from mypy.util import hash_digest, json_dumps
 from mypyc.analysis.capsule_deps import find_implicit_op_dependencies
 from mypyc.codegen.cstring import c_string_initializer
-from mypyc.ir.deps import LIBRT_BASE64, LIBRT_STRINGS
-from mypyc.codegen.emit import Emitter, EmitterContext, HeaderDeclaration, c_array_initializer, native_function_doc_initializer
+from mypyc.codegen.emit import (
+    Emitter,
+    EmitterContext,
+    HeaderDeclaration,
+    c_array_initializer,
+    native_function_doc_initializer,
+)
 from mypyc.codegen.emitclass import generate_class, generate_class_reuse, generate_class_type_decl
 from mypyc.codegen.emitfunc import generate_native_function, native_function_header
 from mypyc.codegen.emitwrapper import (
@@ -51,6 +56,7 @@
     short_id_from_name,
 )
 from mypyc.errors import Errors
+from mypyc.ir.deps import LIBRT_BASE64, LIBRT_STRINGS, SourceDep
 from mypyc.ir.func_ir import FuncIR
 from mypyc.ir.module_ir import ModuleIR, ModuleIRs, deserialize_modules
 from mypyc.ir.ops import DeserMaps, LoadLiteral
@@ -424,8 +430,6 @@ def load_scc_from_cache(
 
 def collect_source_dependencies(modules: dict[str, ModuleIR]) -> set[SourceDep]:
     """Collect all SourceDep dependencies from all modules."""
-    from mypyc.ir.deps import SourceDep
-
     source_deps: set[SourceDep] = set()
     for module in modules.values():
         for dep in module.dependencies:
diff --git a/mypyc/ir/deps.py b/mypyc/ir/deps.py
index 01fd060d48197..e29c228c30e68 100644
--- a/mypyc/ir/deps.py
+++ b/mypyc/ir/deps.py
@@ -1,4 +1,4 @@
-from typing import Final, Union
+from typing import Final
 
 
 class Capsule:
@@ -34,10 +34,10 @@ def __hash__(self) -> int:
 
     def get_header(self) -> str:
         """Get the header file path by replacing .c with .h"""
-        return self.path.replace('.c', '.h')
+        return self.path.replace(".c", ".h")
 
 
-Dependency = Union[Capsule, SourceDep]
+Dependency = Capsule | SourceDep
 
 
 LIBRT_STRINGS: Final = Capsule("librt.strings")
diff --git a/mypyc/ir/ops.py b/mypyc/ir/ops.py
index f478156ac41ad..c09872ca38264 100644
--- a/mypyc/ir/ops.py
+++ b/mypyc/ir/ops.py
@@ -31,6 +31,7 @@ class to enable the new behavior. Sometimes adding a new abstract
 
 from mypy_extensions import trait
 
+from mypyc.ir.deps import Dependency
 from mypyc.ir.rtypes import (
     RArray,
     RInstance,
@@ -55,7 +56,6 @@ class to enable the new behavior. Sometimes adding a new abstract
     short_int_rprimitive,
     void_rtype,
 )
-from mypyc.ir.deps import Dependency
 
 if TYPE_CHECKING:
     from mypyc.codegen.literals import LiteralValue
diff --git a/mypyc/primitives/registry.py b/mypyc/primitives/registry.py
index 650800462ac59..a59599f693c4a 100644
--- a/mypyc/primitives/registry.py
+++ b/mypyc/primitives/registry.py
@@ -39,9 +39,9 @@
 
 from typing import Final, NamedTuple
 
+from mypyc.ir.deps import Dependency
 from mypyc.ir.ops import PrimitiveDescription, StealsDescription
 from mypyc.ir.rtypes import RType
-from mypyc.ir.deps import Dependency
 
 # Error kind for functions that return negative integer on exception. This
 # is only used for primitives. We translate it away during IR building.
diff --git a/mypyc/test/test_cheader.py b/mypyc/test/test_cheader.py
index dc975b2b9d418..d21eefdb9bc5c 100644
--- a/mypyc/test/test_cheader.py
+++ b/mypyc/test/test_cheader.py
@@ -7,8 +7,8 @@
 import re
 import unittest
 
-from mypyc.primitives import registry
 from mypyc.ir.deps import SourceDep
+from mypyc.primitives import registry
 
 
 class TestHeaderInclusion(unittest.TestCase):

From 9889e915f02f637ea3658fa6665f8b52d16d8701 Mon Sep 17 00:00:00 2001
From: Jukka Lehtosalo <jukka.lehtosalo@iki.fi>
Date: Wed, 3 Dec 2025 15:27:25 -0700
Subject: [PATCH 5/6] Add test and fix test harness

---
 mypyc/build.py                       |  7 ++++---
 mypyc/test-data/run-multimodule.test | 12 ++++++++++++
 mypyc/test/test_run.py               |  4 +++-
 3 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/mypyc/build.py b/mypyc/build.py
index 198865dc787bb..e55e2e99946ae 100644
--- a/mypyc/build.py
+++ b/mypyc/build.py
@@ -490,7 +490,7 @@ def mypyc_build(
     *,
     separate: bool | list[tuple[list[str], str | None]] = False,
     only_compile_paths: Iterable[str] | None = None,
-    skip_cgen_input: Any | None = None,
+    skip_cgen_input: tuple[list[list[tuple[str, str]]], list[str]] | None = None,
     always_use_shared_lib: bool = False,
 ) -> tuple[emitmodule.Groups, list[tuple[list[str], list[str]]], list[SourceDep]]:
     """Do the front and middle end of mypyc building, producing and writing out C source."""
@@ -523,7 +523,8 @@ def mypyc_build(
         # TODO: unique names?
         write_file(os.path.join(compiler_options.target_dir, "ops.txt"), ops_text)
     else:
-        group_cfiles = skip_cgen_input
+        group_cfiles = skip_cgen_input[0]
+        source_deps = [SourceDep(d) for d in skip_cgen_input[1]]
 
     # Write out the generated C and collect the files for each group
     # Should this be here??
@@ -553,7 +554,7 @@ def mypycify(
     strip_asserts: bool = False,
     multi_file: bool = False,
     separate: bool | list[tuple[list[str], str | None]] = False,
-    skip_cgen_input: Any | None = None,
+    skip_cgen_input: tuple[list[list[tuple[str, str]]], list[str]] | None = None,
     target_dir: str | None = None,
     include_runtime_files: bool | None = None,
     strict_dunder_typing: bool = False,
diff --git a/mypyc/test-data/run-multimodule.test b/mypyc/test-data/run-multimodule.test
index 9323612cb4fbc..216aed25a5e5b 100644
--- a/mypyc/test-data/run-multimodule.test
+++ b/mypyc/test-data/run-multimodule.test
@@ -950,3 +950,15 @@ import native
 15
 NT(x=4)
 {'x': 5}
+
+[case testExtraLibRtSourceFileDep]
+table_list = list(range(256))
+table_list[ord('A')] = ord('B')
+table = bytes(table_list)
+
+def translate(b: bytes) -> bytes:
+    # The primimitive for bytes.translate requires an optional C file from lib-rt
+    return b.translate(table)
+[file driver.py]
+import native
+assert native.translate(b'ABCD') == b'BBCD'
diff --git a/mypyc/test/test_run.py b/mypyc/test/test_run.py
index d332a7466af41..681e15b588448 100644
--- a/mypyc/test/test_run.py
+++ b/mypyc/test/test_run.py
@@ -22,6 +22,7 @@
 from mypy.test.helpers import assert_module_equivalence, perform_file_operations
 from mypyc.build import construct_groups
 from mypyc.codegen import emitmodule
+from mypyc.codegen.emitmodule import collect_source_dependencies
 from mypyc.errors import Errors
 from mypyc.options import CompilerOptions
 from mypyc.test.config import test_data_prefix
@@ -266,6 +267,7 @@ def run_case_step(self, testcase: DataDrivenTestCase, incremental_step: int) ->
             ir, cfiles, _ = emitmodule.compile_modules_to_c(
                 result, compiler_options=compiler_options, errors=errors, groups=groups
             )
+            deps = sorted(dep.path for dep in collect_source_dependencies(ir))
             if errors.num_errors:
                 errors.flush_errors()
                 assert False, "Compile error"
@@ -288,7 +290,7 @@ def run_case_step(self, testcase: DataDrivenTestCase, incremental_step: int) ->
                 setup_format.format(
                     module_paths,
                     separate,
-                    cfiles,
+                    (cfiles, deps),
                     self.multi_file,
                     opt_level,
                     librt,

From 2b6c8b16195896fcd801142a8e48624250abb12e Mon Sep 17 00:00:00 2001
From: Jukka Lehtosalo <jukka.lehtosalo@iki.fi>
Date: Mon, 8 Dec 2025 14:54:32 +0000
Subject: [PATCH 6/6] Update comments and docstrings

---
 mypyc/build.py   | 1 -
 mypyc/ir/deps.py | 8 +++++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/mypyc/build.py b/mypyc/build.py
index e55e2e99946ae..757f0a49737a1 100644
--- a/mypyc/build.py
+++ b/mypyc/build.py
@@ -725,7 +725,6 @@ def mypycify(
             rt_file = os.path.join(build_dir, name)
             with open(os.path.join(include_dir(), name), encoding="utf-8") as f:
                 write_file(rt_file, f.read())
-            # Only add .c files to shared_cfilenames
             if name.endswith(".c"):
                 shared_cfilenames.append(rt_file)
 
diff --git a/mypyc/ir/deps.py b/mypyc/ir/deps.py
index e29c228c30e68..b7747646628b1 100644
--- a/mypyc/ir/deps.py
+++ b/mypyc/ir/deps.py
@@ -5,6 +5,7 @@ class Capsule:
     """Defines a C extension capsule that a primitive may require."""
 
     def __init__(self, name: str) -> None:
+        # Module fullname, e.g. 'librt.base64'
         self.name: Final = name
 
     def __repr__(self) -> str:
@@ -18,9 +19,14 @@ def __hash__(self) -> int:
 
 
 class SourceDep:
-    """Defines a C source file that a primitive may require."""
+    """Defines a C source file that a primitive may require.
+
+    Each source file must also have a corresponding .h file (replace .c with .h)
+    that gets implicitly #included if the source is used.
+    """
 
     def __init__(self, path: str) -> None:
+        # Relative path from mypyc/lib-rt, e.g. 'bytes_extra_ops.c'
         self.path: Final = path
 
     def __repr__(self) -> str: