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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#pragma once
#include "alloc-util.h"
#include "macro.h"
#include "memory-util.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. */
#define _common_static_destruct_attrs_ \
/* Older compilers don't know "retain" attribute. */ \
_Pragma("GCC diagnostic ignored \"-Wattributes\"") \
/* The actual destructor structure we place in a special section to find it. */ \
_section_("SYSTEMD_STATIC_DESTRUCT") \
/* Use pointer alignment, since that is apparently what gcc does for static variables. */ \
_alignptr_ \
/* Make sure this is not dropped from the image despite not being explicitly referenced. */ \
_used_ \
/* Prevent garbage collection by the linker. */ \
_retain_ \
/* Make sure that AddressSanitizer doesn't pad this variable: we want everything in this section
* packed next to each other so that we can enumerate it. */ \
_variable_no_sanitize_address_
typedef enum StaticDestructorType {
STATIC_DESTRUCTOR_SIMPLE,
STATIC_DESTRUCTOR_ARRAY,
_STATIC_DESTRUCTOR_TYPE_MAX,
_STATIC_DESTRUCTOR_INVALID = -EINVAL,
} StaticDestructorType;
typedef struct SimpleCleanup {
void *data;
free_func_t destroy;
} SimpleCleanup;
typedef struct StaticDestructor {
StaticDestructorType type;
union {
SimpleCleanup simple;
ArrayCleanup array;
};
} 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); \
} \
_common_static_destruct_attrs_ \
static const StaticDestructor UNIQ_T(static_destructor_entry, uq) = { \
.type = STATIC_DESTRUCTOR_SIMPLE, \
.simple.data = &(variable), \
.simple.destroy = UNIQ_T(static_destructor_wrapper, uq), \
}
#define STATIC_ARRAY_DESTRUCTOR_REGISTER(a, n, func) \
_STATIC_ARRAY_DESTRUCTOR_REGISTER(UNIQ, a, n, func)
#define _STATIC_ARRAY_DESTRUCTOR_REGISTER(uq, a, n, func) \
/* Type-safety check */ \
_unused_ static void (* UNIQ_T(static_destructor_wrapper, uq))(typeof(a[0]) *x, size_t y) = (func); \
_common_static_destruct_attrs_ \
static const StaticDestructor UNIQ_T(static_destructor_entry, uq) = { \
.type = STATIC_DESTRUCTOR_ARRAY, \
.array.parray = (void**) &(a), \
.array.pn = &(n), \
.array.pfunc = (free_array_func_t) (func), \
};
/* Beginning and end of our section listing the destructors. We define these as weak as we want this to work
* even if no destructors are defined and the section is missing. */
extern const StaticDestructor _weak_ __start_SYSTEMD_STATIC_DESTRUCT[];
extern const StaticDestructor _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) {
if (!__start_SYSTEMD_STATIC_DESTRUCT)
return;
for (const StaticDestructor *d = ALIGN_PTR(__start_SYSTEMD_STATIC_DESTRUCT);
d < __stop_SYSTEMD_STATIC_DESTRUCT;
d = ALIGN_PTR(d + 1))
switch (d->type) {
case STATIC_DESTRUCTOR_SIMPLE:
d->simple.destroy(d->simple.data);
break;
case STATIC_DESTRUCTOR_ARRAY:
array_cleanup(&d->array);
break;
default:
assert_not_reached();
}
}
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