Merge pull request #10845 from poettering/static-destruct

RFC: introduce automatic destructors for static variables

src/ac-power/ac-power.c

@@ -2,6 +2,7 @@
 
 #include <getopt.h>
 
+#include "main-func.h"
 #include "util.h"
 
 static bool arg_verbose = false;

src/basic/macro.h

@@ -506,23 +506,4 @@ static inline int __coverity_check__(int condition) {
         DEFINE_PUBLIC_TRIVIAL_REF_FUNC(type, name);                    \
         DEFINE_PUBLIC_TRIVIAL_UNREF_FUNC(type, name, free_func);
 
-/* Negative return values from impl are mapped to EXIT_FAILURE, and
- * everything else means success! */
-#define DEFINE_MAIN_FUNCTION(impl)                                      \
-        int main(int argc, char *argv[]) {                              \
-                int r;                                                  \
-                r = impl(argc, argv);                                   \
-                return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;             \
-        }
-
-/* Zero is mapped to EXIT_SUCCESS, and both negative and positive values
- * are mapped to EXIT_FAILURE.
- * Note: this means "true" maps to EXIT_FAILURE. */
-#define DEFINE_MAIN_FUNCTION_WITH_POSITIVE_FAILURE(impl)                \
-        int main(int argc, char *argv[]) {                              \
-                int r;                                                  \
-                r = impl(argc, argv);                                   \
-                return r != 0 ? EXIT_FAILURE : EXIT_SUCCESS;            \
-        }
-
 #include "log.h"

src/basic/main-func.h

@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+#pragma once
+
+#include <stdlib.h>
+
+#include "static-destruct.h"
+
+/* Negative return values from impl are mapped to EXIT_FAILURE, and
+ * everything else means success! */
+#define DEFINE_MAIN_FUNCTION(impl)                                      \
+        int main(int argc, char *argv[]) {                              \
+                int r;                                                  \
+                r = impl(argc, argv);                                   \
+                static_destruct();                                      \
+                return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;             \
+        }
+
+/* Zero is mapped to EXIT_SUCCESS, and both negative and positive values
+ * are mapped to EXIT_FAILURE.
+ * Note: this means "true" maps to EXIT_FAILURE. */
+#define DEFINE_MAIN_FUNCTION_WITH_POSITIVE_FAILURE(impl)                \
+        int main(int argc, char *argv[]) {                              \
+                int r;                                                  \
+                r = impl(argc, argv);                                   \
+                static_destruct();                                      \
+                return r != 0 ? EXIT_FAILURE : EXIT_SUCCESS;            \
+        }

src/basic/meson.build

@@ -183,6 +183,7 @@ basic_sources = files('''
         special.h
         stat-util.c
         stat-util.h
+        static-destruct.h
         stdio-util.h
         strbuf.c
         strbuf.h

src/basic/static-destruct.h

@@ -0,0 +1,51 @@
+#pragma once
+
+#include "macro.h"
+
+/* A framework for registering static variables that shall be freed on shutdown of a process. It's a bit like gcc's
+ * destructor attribute, but allows us to precisely schedule when we want to free the variables. This is supposed to
+ * feel a bit like the gcc cleanup attribute, but for static variables. Note that this does not work for static
+ * variables declared in .so's, as the list is private to the same linking unit. But maybe that's a good thing. */
+
+typedef struct StaticDestructor {
+        void *data;
+        void (*destroy)(void *p);
+} StaticDestructor;
+
+#define STATIC_DESTRUCTOR_REGISTER(variable, func) \
+        _STATIC_DESTRUCTOR_REGISTER(UNIQ, variable, func)
+
+#define _STATIC_DESTRUCTOR_REGISTER(uq, variable, func)                 \
+        /* Type-safe destructor */                                      \
+        static void UNIQ_T(static_destructor_wrapper, uq)(void *p) {    \
+                typeof(variable) *q = p;                                \
+                func(q);                                                \
+        }                                                               \
+        /* The actual destructor structure */                           \
+        __attribute__ ((__section__("SYSTEMD_STATIC_DESTRUCT")))        \
+        __attribute__ ((__aligned__(__BIGGEST_ALIGNMENT__)))            \
+        __attribute__ ((__used__))                                      \
+        static const StaticDestructor UNIQ_T(static_destructor_entry, uq) = { \
+                .data = &(variable),                                    \
+                .destroy = UNIQ_T(static_destructor_wrapper, uq),       \
+        }
+
+/* Beginning and end of our section listing the destructors. We define these as weak as we want this to work even if
+ * there's not a single destructor is defined in which case the section will be missing. */
+extern const struct StaticDestructor __attribute__((__weak__)) __start_SYSTEMD_STATIC_DESTRUCT[];
+extern const struct StaticDestructor __attribute__((__weak__)) __stop_SYSTEMD_STATIC_DESTRUCT[];
+
+/* The function to destroy everything. (Note that this must be static inline, as it's key that it remains in the same
+ * linking unit as the variables we want to destroy. */
+static inline void static_destruct(void) {
+        const StaticDestructor *d;
+
+        if (!__start_SYSTEMD_STATIC_DESTRUCT)
+                return;
+
+        d = ALIGN_TO_PTR(__start_SYSTEMD_STATIC_DESTRUCT, __BIGGEST_ALIGNMENT__);
+        while (d < __stop_SYSTEMD_STATIC_DESTRUCT) {
+                d->destroy(d->data);
+                d = ALIGN_TO_PTR(d + 1, __BIGGEST_ALIGNMENT__);
+        }
+}

src/boot/bless-boot.c

@@ -9,6 +9,7 @@
 #include "fd-util.h"
 #include "fs-util.h"
 #include "log.h"
+#include "main-func.h"
 #include "parse-util.h"
 #include "path-util.h"
 #include "util.h"

src/boot/boot-check-no-failures.c

@@ -10,6 +10,7 @@
 #include "alloc-util.h"
 #include "bus-error.h"
 #include "log.h"
+#include "main-func.h"
 #include "util.h"
 
 static int help(void) {

src/cgtop/cgtop.c

@@ -19,6 +19,7 @@
 #include "fd-util.h"
 #include "fileio.h"
 #include "hashmap.h"
+#include "main-func.h"
 #include "parse-util.h"
 #include "path-util.h"
 #include "process-util.h"

src/coredump/coredump.c

@@ -34,6 +34,7 @@
 #include "journal-importer.h"
 #include "log.h"
 #include "macro.h"
+#include "main-func.h"
 #include "missing.h"
 #include "mkdir.h"
 #include "parse-util.h"

src/debug-generator/debug-generator.c

@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: LGPL-2.1+ */
 
 #include "alloc-util.h"
+#include "main-func.h"
 #include "mkdir.h"
 #include "parse-util.h"
 #include "proc-cmdline.h"
@@ -16,6 +17,10 @@ static char **arg_mask = NULL;
 static char **arg_wants = NULL;
 static bool arg_debug_shell = false;
 
+STATIC_DESTRUCTOR_REGISTER(arg_default_unit, freep);
+STATIC_DESTRUCTOR_REGISTER(arg_mask, strv_freep);
+STATIC_DESTRUCTOR_REGISTER(arg_wants, strv_freep);
+
 static int parse_proc_cmdline_item(const char *key, const char *value, void *data) {
         int r;
 
@@ -136,12 +141,12 @@ static int generate_wants_symlinks(void) {
         return r;
 }
 
-int main(int argc, char *argv[]) {
+static int run(int argc, char *argv[]) {
         int r, q;
 
         if (argc > 1 && argc != 4) {
                 log_error("This program takes three or no arguments.");
-                return EXIT_FAILURE;
+                return -EINVAL;
         }
 
         if (argc > 1)
@@ -160,22 +165,14 @@ int main(int argc, char *argv[]) {
 
         if (arg_debug_shell) {
                 r = strv_extend(&arg_wants, "debug-shell.service");
-                if (r < 0) {
-                        r = log_oom();
-                        goto finish;
-                }
+                if (r < 0)
+                        return log_oom();
         }
 
         r = generate_mask_symlinks();
-
         q = generate_wants_symlinks();
-        if (q < 0)
-                r = q;
 
-finish:
-        arg_default_unit = mfree(arg_default_unit);
-        strv_free(arg_wants);
-        strv_free(arg_mask);
-
-        return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
+        return r < 0 ? r : q;
 }
+
+DEFINE_MAIN_FUNCTION(run);

src/detect-virt/detect-virt.c

@@ -6,6 +6,7 @@
 #include <stdlib.h>
 
 #include "alloc-util.h"
+#include "main-func.h"
 #include "string-table.h"
 #include "terminal-util.h"
 #include "util.h"

src/escape/escape.c

@@ -6,6 +6,7 @@
 
 #include "alloc-util.h"
 #include "log.h"
+#include "main-func.h"
 #include "string-util.h"
 #include "strv.h"
 #include "terminal-util.h"

src/fsck/fsck.c

@@ -22,6 +22,7 @@
 #include "device-util.h"
 #include "fd-util.h"
 #include "fs-util.h"
+#include "main-func.h"
 #include "parse-util.h"
 #include "path-util.h"
 #include "proc-cmdline.h"

src/hostname/hostnamectl.c

@@ -14,6 +14,7 @@
 #include "bus-error.h"
 #include "bus-util.h"
 #include "hostname-util.h"
+#include "main-func.h"
 #include "spawn-polkit-agent.h"
 #include "terminal-util.h"
 #include "util.h"

src/hwdb/hwdb.c

@@ -6,6 +6,7 @@
 
 #include "alloc-util.h"
 #include "hwdb-util.h"
+#include "main-func.h"
 #include "selinux-util.h"
 #include "terminal-util.h"
 #include "util.h"

src/id128/id128.c

@@ -5,6 +5,7 @@
 
 #include "alloc-util.h"
 #include "id128-print.h"
+#include "main-func.h"
 #include "terminal-util.h"
 #include "util.h"
 #include "verbs.h"

src/import/export.c

@@ -13,6 +13,7 @@
 #include "hostname-util.h"
 #include "import-util.h"
 #include "machine-image.h"
+#include "main-func.h"
 #include "signal-util.h"
 #include "string-util.h"
 #include "verbs.h"

src/import/import.c

@@ -13,6 +13,7 @@
 #include "import-tar.h"
 #include "import-util.h"
 #include "machine-image.h"
+#include "main-func.h"
 #include "signal-util.h"
 #include "string-util.h"
 #include "verbs.h"

src/import/importd.c

@@ -13,6 +13,7 @@
 #include "hostname-util.h"
 #include "import-util.h"
 #include "machine-pool.h"
+#include "main-func.h"
 #include "missing.h"
 #include "mkdir.h"
 #include "parse-util.h"

src/import/pull.c

@@ -9,6 +9,7 @@
 #include "hostname-util.h"
 #include "import-util.h"
 #include "machine-image.h"
+#include "main-func.h"
 #include "parse-util.h"
 #include "pull-raw.h"
 #include "pull-tar.h"

src/journal/cat.c

@@ -11,11 +11,12 @@
 
 #include "alloc-util.h"
 #include "fd-util.h"
+#include "main-func.h"
 #include "parse-util.h"
 #include "string-util.h"
 #include "syslog-util.h"
-#include "util.h"
 #include "terminal-util.h"
+#include "util.h"
 
 static const char *arg_identifier = NULL;
 static int arg_priority = LOG_INFO;

src/login/inhibit.c

@@ -14,6 +14,7 @@
 #include "fd-util.h"
 #include "format-table.h"
 #include "format-util.h"
+#include "main-func.h"
 #include "pager.h"
 #include "process-util.h"
 #include "signal-util.h"

src/login/logind.c

@@ -19,6 +19,7 @@
 #include "format-util.h"
 #include "fs-util.h"
 #include "logind.h"
+#include "main-func.h"
 #include "parse-util.h"
 #include "process-util.h"
 #include "selinux-util.h"

src/login/user-runtime-dir.c

@@ -8,6 +8,7 @@
 #include "bus-error.h"
 #include "fs-util.h"
 #include "label.h"
+#include "main-func.h"
 #include "mkdir.h"
 #include "mount-util.h"
 #include "path-util.h"

src/machine/machined.c

@@ -17,6 +17,7 @@
 #include "label.h"
 #include "machine-image.h"
 #include "machined.h"
+#include "main-func.h"
 #include "process-util.h"
 #include "signal-util.h"
 #include "special.h"

src/notify/notify.c

@@ -12,6 +12,7 @@
 #include "env-util.h"
 #include "format-util.h"
 #include "log.h"
+#include "main-func.h"
 #include "parse-util.h"
 #include "string-util.h"
 #include "strv.h"

src/partition/makefs.c

@@ -11,6 +11,7 @@
 
 #include "alloc-util.h"
 #include "dissect-image.h"
+#include "main-func.h"
 #include "process-util.h"
 #include "signal-util.h"
 #include "string-util.h"

src/path/path.c

@@ -10,6 +10,7 @@
 #include "alloc-util.h"
 #include "log.h"
 #include "macro.h"
+#include "main-func.h"
 #include "string-util.h"
 #include "terminal-util.h"
 #include "util.h"

src/portable/portabled.c

@@ -6,6 +6,7 @@
 #include "alloc-util.h"
 #include "bus-util.h"
 #include "def.h"
+#include "main-func.h"
 #include "portabled-bus.h"
 #include "portabled-image-bus.h"
 #include "portabled.h"

src/quotacheck/quotacheck.c

@@ -6,6 +6,7 @@
 #include <sys/prctl.h>
 #include <unistd.h>
 
+#include "main-func.h"
 #include "proc-cmdline.h"
 #include "process-util.h"
 #include "signal-util.h"

src/random-seed/random-seed.c

@@ -12,6 +12,7 @@
 #include "fd-util.h"
 #include "io-util.h"
 #include "log.h"
+#include "main-func.h"
 #include "mkdir.h"
 #include "string-util.h"
 #include "util.h"

src/remount-fs/remount-fs.c

@@ -10,6 +10,7 @@
 
 #include "exit-status.h"
 #include "log.h"
+#include "main-func.h"
 #include "mount-setup.h"
 #include "mount-util.h"
 #include "path-util.h"

src/sleep/sleep.c

@@ -16,6 +16,7 @@
 #include "fd-util.h"
 #include "fileio.h"
 #include "log.h"
+#include "main-func.h"
 #include "parse-util.h"
 #include "sleep-config.h"
 #include "stdio-util.h"

src/stdio-bridge/stdio-bridge.c

@@ -11,10 +11,11 @@
 #include "sd-daemon.h"
 
 #include "alloc-util.h"
+#include "build.h"
 #include "bus-internal.h"
 #include "bus-util.h"
-#include "build.h"
 #include "log.h"
+#include "main-func.h"
 #include "util.h"
 
 #define DEFAULT_BUS_PATH "unix:path=/run/dbus/system_bus_socket"

src/sysv-generator/sysv-generator.c

@@ -14,6 +14,7 @@
 #include "hexdecoct.h"
 #include "install.h"
 #include "log.h"
+#include "main-func.h"
 #include "mkdir.h"
 #include "path-lookup.h"
 #include "path-util.h"

src/tty-ask-password-agent/tty-ask-password-agent.c

@@ -30,6 +30,7 @@
 #include "hashmap.h"
 #include "io-util.h"
 #include "macro.h"
+#include "main-func.h"
 #include "mkdir.h"
 #include "path-util.h"
 #include "process-util.h"

src/volatile-root/volatile-root.c

@@ -4,12 +4,13 @@
 
 #include "alloc-util.h"
 #include "fs-util.h"
+#include "main-func.h"
 #include "mkdir.h"
 #include "mount-util.h"
-#include "stat-util.h"
-#include "volatile-util.h"
-#include "string-util.h"
 #include "path-util.h"
+#include "stat-util.h"
+#include "string-util.h"
+#include "volatile-util.h"
 
 static int make_volatile(const char *path) {
         _cleanup_free_ char *old_usr = NULL;