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https://github.com/jart/cosmopolitan.git
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33e8fc8687
You can now do epic things like this:
puts(_gc(xasprintf("%d", 123)));
The _gc() API is shorthand for _defer() which works like Go's keyword:
const char *s = xasprintf("%d", 123);
_defer(free, s);
puts(s);
Be sure to always use -fno-omit-frame-pointer which makes code fast too.
Enjoy! See also #114
66 lines
3.3 KiB
C
66 lines
3.3 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2021 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/nexgen32e/stackframe.h"
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#include "libc/runtime/gc.h"
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#include "libc/runtime/runtime.h"
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/**
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* Frees memory when function returns.
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*
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* This garbage collector overwrites the return address on the stack so
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* that the RET instruction calls a trampoline which calls free(). It's
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* loosely analogous to Go's defer keyword rather than a true cycle gc.
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*
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* const char *s = _gc(strdup("hello"));
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* puts(s);
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*
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* This macro is equivalent to:
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*
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* _defer(free, ptr)
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*
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* @warning do not return a gc()'d pointer
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* @warning do not realloc() with gc()'d pointer
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* @warning be careful about static keyword due to impact of inlining
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* @note you should use -fno-omit-frame-pointer
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*/
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void *(_gc)(void *thing) {
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struct StackFrame *frame;
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frame = __builtin_frame_address(0);
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__deferer(frame->next, _weakfree, thing);
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return thing;
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}
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/**
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* Calls fn(arg) when function returns.
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*
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* This garbage collector overwrites the return address on the stack so
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* that the RET instruction calls a trampoline which calls free(). It's
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* loosely analogous to Go's defer keyword rather than a true cycle gc.
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*
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* @warning do not return a gc()'d pointer
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* @warning do not realloc() with gc()'d pointer
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* @warning be careful about static keyword due to impact of inlining
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* @note you should use -fno-omit-frame-pointer
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*/
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void *(_defer)(void *fn, void *arg) {
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struct StackFrame *frame;
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frame = __builtin_frame_address(0);
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__deferer(frame->next, fn, arg);
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return arg;
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}
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