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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#pragma once
#include "alloc-util.h"
#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;
free_func_t destroy;
} 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); \
} \
/* 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_ \
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 no destructors are defined and the section is missing. */
extern const struct StaticDestructor _weak_ __start_SYSTEMD_STATIC_DESTRUCT[];
extern const struct 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) {
const StaticDestructor *d;
if (!__start_SYSTEMD_STATIC_DESTRUCT)
return;
d = ALIGN_PTR(__start_SYSTEMD_STATIC_DESTRUCT);
while (d < __stop_SYSTEMD_STATIC_DESTRUCT) {
d->destroy(d->data);
d = ALIGN_PTR(d + 1);
}
}
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