tree-wide: reset the cleaned-up variable in cleanup functions

If the cleanup function returns the appropriate type, use that to reset the
variable. For other functions (usually the foreign ones which return void), add
an explicit value to reset to.

This causes a bit of code churn, but I think it might be worth it. In a
following patch static destructors will be called from a fuzzer, and this
change allows them to be called multiple times. But I think such a change might
help with detecting unitialized code reuse too. We hit various bugs like this,
and things are more obvious when a pointer has been set to NULL.

I was worried whether this change increases text size, but it doesn't seem to:

-Dbuildtype=debug:
before "tree-wide: return NULL from freeing functions":
-rwxrwxr-x 1 zbyszek zbyszek 4117672 Feb 16 14:36 build/libsystemd.so.0.30.0*
-rwxrwxr-x 1 zbyszek zbyszek 4494520 Feb 16 15:06 build/systemd*
after "tree-wide: return NULL from freeing functions":
-rwxrwxr-x 1 zbyszek zbyszek 4117672 Feb 16 14:36 build/libsystemd.so.0.30.0*
-rwxrwxr-x 1 zbyszek zbyszek 4494576 Feb 16 15:10 build/systemd*
now:
-rwxrwxr-x 1 zbyszek zbyszek 4117672 Feb 16 14:36 build/libsystemd.so.0.30.0*
-rwxrwxr-x 1 zbyszek zbyszek 4494640 Feb 16 15:15 build/systemd*

-Dbuildtype=release:
before "tree-wide: return NULL from freeing functions":
-rwxrwxr-x 1 zbyszek zbyszek 5252256 Feb 14 14:47 build-rawhide/libsystemd.so.0.30.0*
-rwxrwxr-x 1 zbyszek zbyszek 1834184 Feb 16 15:09 build-rawhide/systemd*
after "tree-wide: return NULL from freeing functions":
-rwxrwxr-x 1 zbyszek zbyszek 5252256 Feb 14 14:47 build-rawhide/libsystemd.so.0.30.0*
-rwxrwxr-x 1 zbyszek zbyszek 1834184 Feb 16 15:10 build-rawhide/systemd*
now:
-rwxrwxr-x 1 zbyszek zbyszek 5252256 Feb 14 14:47 build-rawhide/libsystemd.so.0.30.0*
-rwxrwxr-x 1 zbyszek zbyszek 1834184 Feb 16 15:16 build-rawhide/systemd*

I would expect that the compiler would be able to elide the setting of a
variable if the variable is never used again. And this seems to be the case:
in optimized builds there is no change in size whatsoever. And the change in
size in unoptimized build is negligible.

Something strange is happening with size of libsystemd: it's bigger in
optimized builds. Something to figure out, but unrelated to this patch.

src/shared/acl-util.h

@@ -21,13 +21,13 @@ int fd_add_uid_acl_permission(int fd, uid_t uid, unsigned mask);
 
 /* acl_free takes multiple argument types.
  * Multiple cleanup functions are necessary. */
-DEFINE_TRIVIAL_CLEANUP_FUNC(acl_t, acl_free);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(acl_t, acl_free, NULL);
 #define acl_free_charp acl_free
-DEFINE_TRIVIAL_CLEANUP_FUNC(char*, acl_free_charp);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(char*, acl_free_charp, NULL);
 #define acl_free_uid_tp acl_free
-DEFINE_TRIVIAL_CLEANUP_FUNC(uid_t*, acl_free_uid_tp);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(uid_t*, acl_free_uid_tp, NULL);
 #define acl_free_gid_tp acl_free
-DEFINE_TRIVIAL_CLEANUP_FUNC(gid_t*, acl_free_gid_tp);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(gid_t*, acl_free_gid_tp, NULL);
 
 #else
 #define ACL_READ    0x04

src/shared/blkid-util.h

@@ -6,5 +6,5 @@
 
 #  include "macro.h"
 
-DEFINE_TRIVIAL_CLEANUP_FUNC(blkid_probe, blkid_free_probe);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(blkid_probe, blkid_free_probe, NULL);
 #endif

src/shared/cryptsetup-util.h

@@ -50,8 +50,8 @@ static inline int sym_crypt_token_max(_unused_ const char *type) {
 
 int dlopen_cryptsetup(void);
 
-DEFINE_TRIVIAL_CLEANUP_FUNC(struct crypt_device *, crypt_free);
-DEFINE_TRIVIAL_CLEANUP_FUNC(struct crypt_device *, sym_crypt_free);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(struct crypt_device *, crypt_free, NULL);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(struct crypt_device *, sym_crypt_free, NULL);
 
 void cryptsetup_enable_logging(struct crypt_device *cd);
 

src/shared/firewall-util-iptables.c

@@ -27,7 +27,7 @@
 #include "macro.h"
 #include "socket-util.h"
 
-DEFINE_TRIVIAL_CLEANUP_FUNC(struct xtc_handle*, iptc_free);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(struct xtc_handle*, iptc_free, NULL);
 
 static int entry_fill_basics(
                 struct ipt_entry *entry,

src/shared/libmount-util.h

@@ -8,8 +8,8 @@
 
 #include "macro.h"
 
-DEFINE_TRIVIAL_CLEANUP_FUNC(struct libmnt_table*, mnt_free_table);
-DEFINE_TRIVIAL_CLEANUP_FUNC(struct libmnt_iter*, mnt_free_iter);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(struct libmnt_table*, mnt_free_table, NULL);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(struct libmnt_iter*, mnt_free_iter, NULL);
 
 static inline int libmount_parse(
                 const char *path,

src/shared/module-util.h

@@ -7,6 +7,6 @@
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(struct kmod_ctx*, kmod_unref);
 DEFINE_TRIVIAL_CLEANUP_FUNC(struct kmod_module*, kmod_module_unref);
-DEFINE_TRIVIAL_CLEANUP_FUNC(struct kmod_list*, kmod_module_unref_list);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(struct kmod_list*, kmod_module_unref_list, NULL);
 
 int module_load_and_warn(struct kmod_ctx *ctx, const char *module, bool verbose);

src/shared/mount-util.h

@@ -45,7 +45,7 @@ int bind_remount_one_with_mountinfo(const char *path, unsigned long new_flags, u
 
 int mount_move_root(const char *path);
 
-DEFINE_TRIVIAL_CLEANUP_FUNC(FILE*, endmntent);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(FILE*, endmntent, NULL);
 #define _cleanup_endmntent_ _cleanup_(endmntentp)
 
 int mount_verbose_full(

src/shared/openssl-util.h

@@ -6,10 +6,10 @@
 #if HAVE_OPENSSL
 #  include <openssl/pem.h>
 
-DEFINE_TRIVIAL_CLEANUP_FUNC(X509*, X509_free);
-DEFINE_TRIVIAL_CLEANUP_FUNC(X509_NAME*, X509_NAME_free);
-DEFINE_TRIVIAL_CLEANUP_FUNC(EVP_PKEY_CTX*, EVP_PKEY_CTX_free);
-DEFINE_TRIVIAL_CLEANUP_FUNC(EVP_CIPHER_CTX*, EVP_CIPHER_CTX_free);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(X509*, X509_free, NULL);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(X509_NAME*, X509_NAME_free, NULL);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(EVP_PKEY_CTX*, EVP_PKEY_CTX_free, NULL);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(EVP_CIPHER_CTX*, EVP_CIPHER_CTX_free, NULL);
 
 int rsa_encrypt_bytes(EVP_PKEY *pkey, const void *decrypted_key, size_t decrypted_key_size, void **ret_encrypt_key, size_t *ret_encrypt_key_size);
 

src/shared/pkcs11-util.h

@@ -21,8 +21,8 @@ P11KitUri *uri_from_module_info(const CK_INFO *info);
 P11KitUri *uri_from_slot_info(const CK_SLOT_INFO *slot_info);
 P11KitUri *uri_from_token_info(const CK_TOKEN_INFO *token_info);
 
-DEFINE_TRIVIAL_CLEANUP_FUNC(P11KitUri*, p11_kit_uri_free);
-DEFINE_TRIVIAL_CLEANUP_FUNC(CK_FUNCTION_LIST**, p11_kit_modules_finalize_and_release);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(P11KitUri*, p11_kit_uri_free, NULL);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(CK_FUNCTION_LIST**, p11_kit_modules_finalize_and_release, NULL);
 
 CK_RV pkcs11_get_slot_list_malloc(CK_FUNCTION_LIST *m, CK_SLOT_ID **ret_slotids, CK_ULONG *ret_n_slotids);
 

src/shared/pwquality-util.h

@@ -19,7 +19,7 @@ extern const char* (*sym_pwquality_strerror)(char *buf, size_t len, int errcode,
 
 int dlopen_pwquality(void);
 
-DEFINE_TRIVIAL_CLEANUP_FUNC(pwquality_settings_t*, sym_pwquality_free_settings);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(pwquality_settings_t*, sym_pwquality_free_settings, NULL);
 
 void pwq_maybe_disable_dictionary(pwquality_settings_t *pwq);
 int pwq_allocate_context(pwquality_settings_t **ret);

src/shared/seccomp-util.h

@@ -121,7 +121,7 @@ extern uint32_t seccomp_local_archs[];
 #define ERRNO_IS_SECCOMP_FATAL(r)                                       \
         IN_SET(abs(r), EPERM, EACCES, ENOMEM, EFAULT)
 
-DEFINE_TRIVIAL_CLEANUP_FUNC(scmp_filter_ctx, seccomp_release);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(scmp_filter_ctx, seccomp_release, NULL);
 
 int parse_syscall_archs(char **l, Set **ret_archs);