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Bring back gc() function

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Renaming gc() to _gc() was a mistake since the better thing to do is put
it behind the _COSMO_SOURCE macro. We need this change because I haven't
wanted to use my amazing garbage collector ever since we renamed it. You
now need to define _COSMO_SOURCE yourself when using amalgamation header
and cosmocc users need to pass the -mcosmo flag to get the gc() function

Some other issues relating to cancelation have been fixed along the way.
We're also now putting cosmocc in a folder named `.cosmocc` so it can be
more safely excluded by grep --exclude-dir=.cosmocc --exclude-dir=o etc.
This commit is contained in:
Justine Tunney 2024-01-08 10:07:35 -08:00
parent 6cb0354e19
commit a4b455185b
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GPG key ID: BE714B4575D6E328
280 changed files with 1362 additions and 1407 deletions
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49
libc/mem/gc.c
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@ -39,7 +39,7 @@ static void TeardownGc(void) {
if (__tls_enabled) {
t = __get_tls();
if ((g = t->tib_garbages)) {
// exit() currently doesn't use _gclongjmp() like pthread_exit()
// exit() currently doesn't use gclongjmp() like pthread_exit()
// so we need to run the deferred functions manually.
while (g->i) {
--g->i;
@ -88,7 +88,7 @@ static void DeferFunction(struct StackFrame *frame, void *fn, void *arg) {
frame->addr = (intptr_t)__gc;
}
// the gnu extension macros for _gc / _defer point here
// the gnu extension macros for gc / defer point here
void __defer(void *rbp, void *fn, void *arg) {
struct StackFrame *f, *frame = rbp;
f = __builtin_frame_address(0);
@ -96,48 +96,3 @@ void __defer(void *rbp, void *fn, void *arg) {
unassert(PointerNotOwnedByParentStackFrame(f, frame, arg));
DeferFunction(frame, fn, arg);
}
/**
* Frees memory when function returns.
*
* This garbage collector overwrites the return address on the stack so
* that the RET instruction calls a trampoline which calls free(). It's
* loosely analogous to Go's defer keyword rather than a true cycle gc.
*
* const char *s = _gc(strdup("hello"));
* puts(s);
*
* This macro is equivalent to:
*
* _defer(free, ptr)
*
* @warning do not return a gc()'d pointer
* @warning do not realloc() with gc()'d pointer
* @warning be careful about static keyword due to impact of inlining
* @note you should use -fno-omit-frame-pointer
*/
void *(_gc)(void *thing) {
struct StackFrame *frame;
frame = __builtin_frame_address(0);
DeferFunction(frame->next, _weakfree, thing);
return thing;
}
/**
* Calls fn(arg) when function returns.
*
* This garbage collector overwrites the return address on the stack so
* that the RET instruction calls a trampoline which calls free(). It's
* loosely analogous to Go's defer keyword rather than a true cycle gc.
*
* @warning do not return a gc()'d pointer
* @warning do not realloc() with gc()'d pointer
* @warning be careful about static keyword due to impact of inlining
* @note you should use -fno-omit-frame-pointer
*/
void *(_defer)(void *fn, void *arg) {
struct StackFrame *frame;
frame = __builtin_frame_address(0);
DeferFunction(frame->next, fn, arg);
return arg;
}