diff --git a/maint/gen_abi.py b/maint/gen_abi.py
index d449339aabd..826bc747b94 100644
--- a/maint/gen_abi.py
+++ b/maint/gen_abi.py
@@ -25,6 +25,7 @@ def search(pat, str, flags=0):
 def main():
     load_mpi_abi_h("src/binding/abi/mpi_abi.h")
     dump_mpi_abi_internal_h("src/binding/abi/mpi_abi_internal.h")
+    dump_io_abi_internal_h("src/binding/abi/io_abi_internal.h")
     dump_romio_abi_internal_h("src/mpi/romio/include/romio_abi_internal.h")
     dump_mpi_abi_util_c("src/binding/abi/mpi_abi_util.c")
 
@@ -101,7 +102,7 @@ def gen_mpi_abi_internal_h(out):
         for line in output_lines:
             print(line, file=Out)
         print("", file=Out)
-        
+
         print("#endif /* MPI_ABI_INTERNAL_H_INCLUDED */", file=Out)
 
 def dump_romio_abi_internal_h(romio_abi_internal_h):
@@ -181,6 +182,52 @@ def add_other(out):
         print("#define ROMIO_ABI_INTERNAL_H_INCLUDED", file=Out)
         print("", file=Out)
 
+        for line in output_lines:
+            print(line, file=Out)
+        print("", file=Out)
+
+        print("#endif /* ROMIO_ABI_INTERNAL_H_INCLUDED */", file=Out)
+
+# similar to romio_abi_internal.h but for use in the mpich io binding
+def dump_io_abi_internal_h(io_abi_internal_h):
+    def gen_io_abi_internal_h(out):
+        for line in G.abi_h_lines:
+            if RE.search(r'MPI_ABI_H_INCLUDED', line):
+                # skip the include guard, harmless
+                pass
+            elif RE.match(r'typedef struct.*\bMPI_File;\s*$', line):
+                out.append("typedef struct ADIOI_FileD *MPI_File;")
+            elif RE.match(r'(int|double|MPI_\w+) (P?MPI\w+)\((.*)\);', line):
+                # prototypes, rename param prefix, add MPICH_API_PUBLIC
+                (T, name, param) = RE.m.group(1,2,3)
+                if RE.match(r'P?MPI_(File_\w+|Register_datarep\w*)', name):
+                    out.append("%s %s(%s) MPICH_API_PUBLIC;" % (T, name, param))
+                else:
+                    out.append("%s %s(%s);" % (T, name, param))
+            else:
+                # replace param prefix
+                out.append(line.rstrip())
+
+    def add_mpich_visibility(out):
+        out.append("#if defined(HAVE_VISIBILITY)")
+        out.append("#define MPICH_API_PUBLIC __attribute__((visibility (\"default\")))")
+        out.append("#else")
+        out.append("#define MPICH_API_PUBLIC")
+        out.append("#endif")
+        out.append("")
+
+    # ----
+    output_lines = []
+    add_mpich_visibility(output_lines)
+    gen_io_abi_internal_h(output_lines)
+
+    print(" --> [%s]" % io_abi_internal_h)
+    with open(io_abi_internal_h, "w") as Out:
+        dump_copyright(Out)
+        print("#ifndef ROMIO_ABI_INTERNAL_H_INCLUDED", file=Out)
+        print("#define ROMIO_ABI_INTERNAL_H_INCLUDED", file=Out)
+        print("", file=Out)
+
         for line in output_lines:
             print(line, file=Out)
         print("", file=Out)
diff --git a/maint/gen_binding_c.py b/maint/gen_binding_c.py
index 60a18b62187..4ed9ce07c1f 100644
--- a/maint/gen_binding_c.py
+++ b/maint/gen_binding_c.py
@@ -145,46 +145,39 @@ def dump_c_binding_abi():
         G.check_write_path(abi_file_path)
         dump_c_file(abi_file_path, G.out)
 
-    def dump_io_funcs(do_abi=False):
+    def dump_io_funcs():
+        G.io_impl_declares = []
         G.out = []
         G.out.append("#include \"mpiimpl.h\"")
-        if do_abi:
-            G.out.append("#include \"mpi_abi_util.h\"")
+        G.out.append("#include \"mpir_io_impl.h\"")
         G.out.append("")
-        # Add a couple direct impl prototypes
-        G.out.append("void MPIR_Ext_cs_enter(void);")
-        G.out.append("void MPIR_Ext_cs_exit(void);")
-        G.out.append("#ifndef HAVE_ROMIO")
-        G.out.append("#define MPIO_Err_return_file(fh, errorcode) MPIR_Err_return_comm(0, __func__, errorcode)")
-        G.out.append("#else")
-        G.out.append("MPI_Fint MPIR_File_c2f_impl(MPI_File fh);")
-        G.out.append("MPI_File MPIR_File_f2c_impl(MPI_Fint fh);")
-        G.out.append("int MPIO_Err_return_file(MPI_File fh, int errorcode);")
-        G.out.append("#endif")
-
-        G.doc3_src_txt = []
-        G.poly_aliases = [] # large-count mansrc aliases
 
         for func in io_func_list:
             G.err_codes = {}
             manpage_out = []
-            if not do_abi:
-                dump_func(func, manpage_out)
-            else:
-                dump_func_abi(func)
-
-        if not do_abi:
-            dump_out(c_dir + "/io.c")
-        else:
-            abi_file_path = abi_dir + "/io_abi.c"
-            G.check_write_path(abi_file_path)
-            dump_c_file(abi_file_path, G.out)
+            dump_func(func, manpage_out)
+
+        dump_out(c_dir + "/io.c")
+
+    def dump_io_funcs_abi():
+        G.out = []
+        G.out.append("#include \"mpichconf.h\"")
+        G.out.append("#include \"io_abi_internal.h\"")
+        G.out.append("#include \"mpir_io_impl.h\"")
+        G.out.append("")
+
+        for func in io_func_list:
+            dump_func_abi(func)
+
+        abi_file_path = abi_dir + "/io_abi.c"
+        G.check_write_path(abi_file_path)
+        dump_c_file(abi_file_path, G.out)
 
     # ----
     dump_c_binding()
     dump_c_binding_abi()
     dump_io_funcs()
-    dump_io_funcs(True)
+    dump_io_funcs_abi()
 
     if 'output-mansrc' in G.opts:
         f = c_dir + '/mansrc/' + 'poly_aliases.lst'
@@ -198,6 +191,7 @@ def dump_io_funcs(do_abi=False):
     G.check_write_path("src/include/mpi_proto.h")
     dump_Makefile_mk("%s/Makefile.mk" % c_dir)
     dump_mpir_impl_h("src/include/mpir_impl.h")
+    dump_mpir_io_impl_h("src/include/mpir_io_impl.h")
     dump_errnames_txt("%s/errnames.txt" % c_dir)
     dump_qmpi_register_h("src/mpi_t/qmpi_register.h")
     dump_mpi_proto_h("src/include/mpi_proto.h")
diff --git a/maint/local_python/binding_c.py b/maint/local_python/binding_c.py
index 1e74702be54..7abbb671834 100644
--- a/maint/local_python/binding_c.py
+++ b/maint/local_python/binding_c.py
@@ -81,14 +81,15 @@ def dump_romio_reference(name):
 
     dump_profiling(func)
 
-    if 'polymorph' in func:
+    if func['dir'] == 'io':
+        dump_function_io(func)
+    elif 'polymorph' in func:
         # MPII_ function to support C/Fortran Polymorphism, eg MPI_Comm_get_attr
         G.out.append("#ifndef MPICH_MPI_FROM_PMPI")
         dump_function_internal(func, kind="polymorph")
         G.out.append("#endif /* MPICH_MPI_FROM_PMPI */")
         G.out.append("")
 
-    if 'polymorph' in func:
         dump_function_internal(func, kind="call-polymorph")
     elif 'replace' in func and 'body' not in func:
         pass
@@ -208,6 +209,32 @@ def dump_mpix_symbols():
         print("", file=Out)
         print("#endif /* MPIR_IMPL_H_INCLUDED */", file=Out)
 
+def dump_mpir_io_impl_h(f):
+    print("  --> [%s]" %f)
+    with open(f, "w") as Out:
+        for l in G.copyright_c:
+            print(l, file=Out)
+        print("#ifndef MPIR_IO_IMPL_H_INCLUDED", file=Out)
+        print("#define MPIR_IO_IMPL_H_INCLUDED", file=Out)
+
+        print("", file=Out)
+        print("void MPIR_Ext_cs_enter(void);", file=Out)
+        print("void MPIR_Ext_cs_exit(void);", file=Out)
+        print("#ifndef HAVE_ROMIO", file=Out)
+        print("int MPIR_Err_return_comm(void *, const char[], int);", file=Out)
+        print("#define MPIO_Err_return_file(fh, errorcode) MPIR_Err_return_comm((void *)0, __func__, errorcode)", file=Out)
+        print("#else", file=Out)
+        print("MPI_Fint MPIR_File_c2f_impl(MPI_File fh);", file=Out)
+        print("MPI_File MPIR_File_f2c_impl(MPI_Fint fh);", file=Out)
+        print("int MPIO_Err_return_file(MPI_File fh, int errorcode);", file=Out)
+        print("#endif", file=Out)
+
+        print("", file=Out)
+        for l in G.io_impl_declares:
+            print(l, file=Out)
+        print("", file=Out)
+        print("#endif /* MPIR_IO_IMPL_H_INCLUDED */", file=Out)
+
 def filter_out_abi():
     funcname = None
     for l in G.out:
@@ -816,6 +843,62 @@ def dump_copy_right():
     G.out.append(" */")
     G.out.append("")
 
+def dump_function_io(func):
+    is_large = func['_is_large']
+    parameters = ""
+    for p in func['c_parameters']:
+        parameters = parameters + ", " + p['name']
+
+    func_decl = get_declare_function(func, is_large)
+    func_name = get_function_name(func, is_large)
+    # declare impl functions, but only do it once
+    if '_is_abi' not in func and 'return' not in func:
+        if func['_is_large'] and func['_poly_impl'] != "separate":
+            pass
+        else:
+            impl_name = re.sub(r'^MPIX?_', 'MPIR_', func['name']) + "_impl"
+            if func['_is_large'] and func['_poly_impl'] == "separate":
+                impl_name = re.sub(r'_impl$', '_large_impl', impl_name)
+            if func['_impl_param_list']:
+                params = ', '.join(func['_impl_param_list'])
+            else:
+                params="void"
+            G.io_impl_declares.append("int %s(%s);" % (impl_name, params))
+
+    dump_line_with_break(func_decl)
+    G.out.append("{")
+    G.out.append("INDENT")
+    if "impl" in func and func['impl'] == "direct":
+        dump_function_direct(func)
+    else:
+        G.out.append("int mpi_errno = MPI_SUCCESS;")
+        if not '_skip_global_cs' in func:
+            G.out.append("MPIR_Ext_cs_enter();")
+        G.out.append("")
+        G.out.append("#ifndef HAVE_ROMIO")
+        if not '_is_abi' in func:
+            G.out.append("mpi_errno = MPIR_Err_create_code(MPI_SUCCESS, MPIR_ERR_RECOVERABLE, __func__, __LINE__, MPI_ERR_OTHER, \"**notimpl\", 0);")
+        else:
+            G.out.append("mpi_errno = MPI_ERR_INTERN;")
+        G.out.append("goto fn_fail;");
+        G.out.append("#else")
+        dump_body_of_routine(func)
+        G.out.append("#endif")
+        G.out.append("")
+        G.out.append("fn_exit:")
+        if not '_skip_global_cs' in func:
+            G.out.append("MPIR_Ext_cs_exit();")
+        G.out.append("return mpi_errno;")
+        G.out.append("fn_fail:")
+        if '_has_file' in func:
+            G.out.append("mpi_errno = MPIO_Err_return_file(%s, mpi_errno);" % func['_has_file'])
+        else:
+            G.out.append("mpi_errno = MPIO_Err_return_file(MPI_FILE_NULL, mpi_errno);")
+        G.out.append("goto fn_exit;")
+    G.out.append("DEDENT")
+    G.out.append("}")
+    G.out.append("")
+
 def dump_qmpi_wrappers(func, is_large):
     parameters = ""
     for p in func['c_parameters']: