Expose public garbage collector API for C language

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

libc/runtime/gc.internal.h

@@ -1,49 +1,10 @@
-#ifndef COSMOPOLITAN_LIBC_RUNTIME_GC_H_
-#define COSMOPOLITAN_LIBC_RUNTIME_GC_H_
-#include "libc/calls/calls.h"
-#include "libc/nexgen32e/stackframe.h"
-#include "libc/runtime/runtime.h"
+#ifndef COSMOPOLITAN_LIBC_RUNTIME_GC_INTERNAL_H_
+#define COSMOPOLITAN_LIBC_RUNTIME_GC_INTERNAL_H_
+#include "libc/runtime/gc.h"
 #if !(__ASSEMBLER__ + __LINKER__ + 0)
-COSMOPOLITAN_C_START_
 
-/**
- * @fileoverview Cosmopolitan Return-Oriented Garbage Collector.
- *
- * This is the same thing as {@code std::unique_ptr<>} in C++ or the
- * {@code defer} keyword in Go. We harness the power of ROP for good
- * using very few lines of code.
- */
+#define gc(THING)      _gc(THING)
+#define defer(FN, ARG) _defer(FN, ARG)
 
-/**
- * Releases resource when function returns.
- *
- * @warning do not return a gc()'d pointer
- * @warning do not realloc() with gc()'d pointer
- */
-#define gc(THING) defer((void *)weakfree, (void *)(THING))
-
-/**
- * Same as longjmp() but runs gc() / defer() destructors.
- */
-void gclongjmp(jmp_buf, int) nothrow wontreturn paramsnonnull();
-
-/**
- * Calls FN(ARG) when function returns.
- */
-#ifndef __VSCODE_INTELLISENSE__
-#define defer(FN, ARG)                                                 \
-  ({                                                                   \
-    autotype(ARG) Arg = (ARG);                                         \
-    /* prevent weird opts like tail call */                            \
-    asm volatile("" : "+g"(Arg) : : "memory");                         \
-    __defer((struct StackFrame *)__builtin_frame_address(0), FN, Arg); \
-    asm volatile("" : "+g"(Arg) : : "memory");                         \
-    Arg;                                                               \
-  })
-#endif /* __VSCODE_INTELLISENSE__ */
-
-void __defer(struct StackFrame *, void *, void *) hidden paramsnonnull((1, 2));
-
-COSMOPOLITAN_C_END_
 #endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
-#endif /* COSMOPOLITAN_LIBC_RUNTIME_GC_H_ */
+#endif /* COSMOPOLITAN_LIBC_RUNTIME_GC_INTERNAL_H_ */