modpost: use null string instead of NULL pointer for default namespace

The default namespace is the null string, "".

When set, the null string "" is converted to NULL:

  s->namespace = namespace[0] ? NOFAIL(strdup(namespace)) : NULL;

When printed, the NULL pointer is get back to the null string:

  sym->namespace ?: ""

This saves 1 byte memory allocated for "", but loses the readability.

In kernel-space, we strive to save memory, but modpost is a userspace
tool used to build the kernel. On modern systems, such small piece of
memory is not a big deal.

Handle the namespace string as is.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index bc9ef40..a7c979b 100644 (file)
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -300,6 +300,13 @@ static bool contains_namespace(struct list_head *head, const char *namespace)
 {
        struct namespace_list *list;
 
+       /*
+        * The default namespace is null string "", which is always implicitly
+        * contained.
+        */
+       if (!namespace[0])
+               return true;
+
        list_for_each_entry(list, head, list) {
                if (!strcmp(list->namespace, namespace))
                        return true;
@@ -369,7 +376,7 @@ static struct symbol *sym_add_exported(const char *name, struct module *mod,
        s = alloc_symbol(name);
        s->module = mod;
        s->is_gpl_only = gpl_only;
-       s->namespace = namespace[0] ? NOFAIL(strdup(namespace)) : NULL;
+       s->namespace = NOFAIL(strdup(namespace));
        list_add_tail(&s->list, &mod->exported_symbols);
        hash_add_symbol(s);
 
@@ -1829,8 +1836,7 @@ static void check_exports(struct module *mod)
                else
                        basename = mod->name;
 
-               if (exp->namespace &&
-                   !contains_namespace(&mod->imported_namespaces, exp->namespace)) {
+               if (!contains_namespace(&mod->imported_namespaces, exp->namespace)) {
                        modpost_log(allow_missing_ns_imports ? LOG_WARN : LOG_ERROR,
                                    "module %s uses symbol %s from namespace %s, but does not import it.\n",
                                    basename, exp->name, exp->namespace);
@@ -1916,8 +1922,7 @@ static void add_exported_symbols(struct buffer *buf, struct module *mod)
        list_for_each_entry(sym, &mod->exported_symbols, list)
                buf_printf(buf, "KSYMTAB_%s(%s, \"%s\", \"%s\");\n",
                           sym->is_func ? "FUNC" : "DATA", sym->name,
-                          sym->is_gpl_only ? "_gpl" : "",
-                          sym->namespace ?: "");
+                          sym->is_gpl_only ? "_gpl" : "", sym->namespace);
 
        if (!modversions)
                return;
@@ -2185,7 +2190,7 @@ static void write_dump(const char *fname)
                        buf_printf(&buf, "0x%08x\t%s\t%s\tEXPORT_SYMBOL%s\t%s\n",
                                   sym->crc, sym->name, mod->name,
                                   sym->is_gpl_only ? "_GPL" : "",
-                                  sym->namespace ?: "");
+                                  sym->namespace);
                }
        }
        write_buf(&buf, fname);