63e688cc3b
various gcc attribute clean-ups
57 lines
3 KiB
C
57 lines
3 KiB
C
#pragma once
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#include "alloc-util.h"
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#include "macro.h"
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/* A framework for registering static variables that shall be freed on shutdown of a process. It's a bit like gcc's
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* destructor attribute, but allows us to precisely schedule when we want to free the variables. This is supposed to
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* feel a bit like the gcc cleanup attribute, but for static variables. Note that this does not work for static
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* variables declared in .so's, as the list is private to the same linking unit. But maybe that's a good thing. */
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typedef struct StaticDestructor {
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void *data;
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free_func_t destroy;
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} StaticDestructor;
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#define STATIC_DESTRUCTOR_REGISTER(variable, func) \
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_STATIC_DESTRUCTOR_REGISTER(UNIQ, variable, func)
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#define _STATIC_DESTRUCTOR_REGISTER(uq, variable, func) \
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/* Type-safe destructor */ \
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static void UNIQ_T(static_destructor_wrapper, uq)(void *p) { \
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typeof(variable) *q = p; \
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func(q); \
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} \
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/* The actual destructor structure we place in a special section to find it */ \
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_section_("SYSTEMD_STATIC_DESTRUCT") \
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/* We pick pointer alignment, since that is apparently what gcc does for static variables */ \
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_alignptr_ \
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/* Make sure this is not dropped from the image because not explicitly referenced */ \
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_used_ \
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/* 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. */ \
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_variable_no_sanitize_address_ \
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static const StaticDestructor UNIQ_T(static_destructor_entry, uq) = { \
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.data = &(variable), \
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.destroy = UNIQ_T(static_destructor_wrapper, uq), \
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}
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/* Beginning and end of our section listing the destructors. We define these as weak as we want this to work even if
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* there's not a single destructor is defined in which case the section will be missing. */
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extern const struct StaticDestructor _weak_ __start_SYSTEMD_STATIC_DESTRUCT[];
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extern const struct StaticDestructor _weak_ __stop_SYSTEMD_STATIC_DESTRUCT[];
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/* The function to destroy everything. (Note that this must be static inline, as it's key that it remains in the same
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* linking unit as the variables we want to destroy. */
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static inline void static_destruct(void) {
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const StaticDestructor *d;
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if (!__start_SYSTEMD_STATIC_DESTRUCT)
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return;
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d = ALIGN_TO_PTR(__start_SYSTEMD_STATIC_DESTRUCT, sizeof(void*));
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while (d < __stop_SYSTEMD_STATIC_DESTRUCT) {
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d->destroy(d->data);
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d = ALIGN_TO_PTR(d + 1, sizeof(void*));
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}
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}
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