Index: clang-tidy/readability/AvoidConstParamsInDecls.cpp
===================================================================
--- clang-tidy/readability/AvoidConstParamsInDecls.cpp
+++ clang-tidy/readability/AvoidConstParamsInDecls.cpp
@@ -31,7 +31,8 @@
 
 void AvoidConstParamsInDecls::registerMatchers(MatchFinder *Finder) {
   const auto ConstParamDecl =
-      parmVarDecl(hasType(qualType(isConstQualified()))).bind("param");
+      parmVarDecl(hasType(qualType(isConstQualified())),
+                  unless(hasAttr(clang::attr::PassObjectSize))).bind("param");
   Finder->addMatcher(functionDecl(unless(isDefinition()),
                                   has(typeLoc(forEach(ConstParamDecl))))
                          .bind("func"),
Index: test/clang-tidy/readability-avoid-const-params-in-decls.cpp
===================================================================
--- test/clang-tidy/readability-avoid-const-params-in-decls.cpp
+++ test/clang-tidy/readability-avoid-const-params-in-decls.cpp
@@ -65,6 +65,8 @@
 void NF6(const int *const) {}
 void NF7(int, const int) {}
 void NF8(const int, const int) {}
+// pass_object_size requires a const pointer param in definitions.
+void NF9(const char *const __attribute__((pass_object_size(0)))) {}
 
 // Do not match on other stuff
 void NF(const alias_type& i);
@@ -76,3 +78,6 @@
 void NF(const int*);
 void NF(const int* const*);
 void NF(alias_const_type);
+// While pass_object_size only requires a const pointer param in definitions,
+// it's probably best to not complain at users for using it in a decl.
+void NF(const char *const __attribute__((pass_object_size(0))));