Don't use constexpr MD5 for Mojo's IPC hashes

As these files are generated, there's no need to make the compiler
constexpr evaluate these. Also switch these to a more modern hash, as
MD5 has been broken for quite some time.

Bug: 406829393
Change-Id: Ie5f258560339bc4238efe90e38c32bfa98f9983f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6405582
Reviewed-by: Alex Gough <ajgo@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1439852}

mojo/public/tools/bindings/generators/cpp_templates/interface_definition.tmpl

@@ -149,14 +149,14 @@ const char* {{interface.name}}::MessageToMethodName_(mojo::Message& message) {
 #if !BUILDFLAG(IS_FUCHSIA)
 {%-   for method in interface.methods %}
 uint32_t {{interface.name}}::{{method.name}}_Sym::IPCStableHash() {
-  // This method's address is used for indetifiying the mojo method name after
+  // This method's address is used for identifiying the mojo method name after
   // symbolization. So each IPCStableHash should have a unique address.
   // We cannot use NO_CODE_FOLDING() here - it relies on the uniqueness of
   // __LINE__ value, which is not unique accross different mojo modules.
   // The code below is very similar to NO_CODE_FOLDING, but it uses a unique
   // hash instead of __LINE__.
-  constexpr uint32_t kHash = base::MD5Hash32Constexpr(
-          "(Impl){{namespace_as_string}}::{{interface.name}}::{{method.name}}");
+{%-     set message_name = "%s::%s::%s"|format(namespace_as_string, interface.name, method.name) %}
+  static constexpr uint32_t kHash = {{message_name|ipc_hash}};  // IPCStableHash for {{message_name}}
   const uint32_t hash = kHash;
   base::debug::Alias(&hash);
   return hash;

mojo/public/tools/bindings/generators/mojom_cpp_generator.py

@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 """Generates C++ source files from a mojom.Module."""
+import hashlib
 import os
 import mojom.generate.generator as generator
 import mojom.generate.module as mojom
@@ -178,6 +179,11 @@ def ShouldInlineUnion(union):
   return not any(mojom.IsReferenceKind(field.kind) for field in union.fields)
 
 
+def _IpcHash(message_name):
+  sha256_hash = hashlib.sha256(message_name.encode('utf-8'))
+  return f'0x{sha256_hash.hexdigest()[:8]}'
+
+
 def HasPackedMethodOrdinals(interface):
   """Returns whether all method ordinals are packed such that indexing into a
   table would be efficient."""
@@ -409,6 +415,7 @@ class Generator(generator.Generator):
         "requires_context_for_data_view": RequiresContextForDataView,
         "should_inline": ShouldInlineStruct,
         "should_inline_union": ShouldInlineUnion,
+        "ipc_hash": _IpcHash,
         "is_array_kind": mojom.IsArrayKind,
         "is_bool_kind": mojom.IsBoolKind,
         "is_default_constructible": self._IsDefaultConstructible,
@@ -550,7 +557,8 @@ class Generator(generator.Generator):
     return self._ExpressionToText(constant.value, kind=constant.kind)
 
   def _ConstantLength(self, constant):
-    # The length of the string value, removing the quotes, but preserving the null-terminator.
+    # The length of the string value, removing the quotes, but preserving the
+    # null-terminator.
     return f"{len(constant.value) - 1}"
 
   def _UnderToCamel(self, value, digits_split=False):