Initial import

libc/runtime/gc.h

@@ -0,0 +1,48 @@
+#ifndef COSMOPOLITAN_LIBC_RUNTIME_GC_H_
+#define COSMOPOLITAN_LIBC_RUNTIME_GC_H_
+#include "libc/calls/calls.h"
+#include "libc/runtime/runtime.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.
+ */
+
+struct StackFrame;
+
+/**
+ * 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(weakfree, (THING))
+
+/**
+ * Same as longjmp() but runs gc() / defer() destructors.
+ */
+void gclongjmp(jmp_buf, int) nothrow noreturn paramsnonnull();
+
+/**
+ * Calls FN(ARG) when function returns.
+ */
+#define defer(FN, ARG)                            \
+  ({                                              \
+    autotype(ARG) Arg = (ARG);                    \
+    /* prevent weird opts like tail call */       \
+    asm volatile("" : "+g"(Arg) : : "memory");    \
+    __defer(__builtin_frame_address(0), FN, Arg); \
+    asm volatile("" : "+g"(Arg) : : "memory");    \
+    Arg;                                          \
+  })
+
+void __defer(struct StackFrame *, void *, void *) hidden paramsnonnull((1, 2));
+
+COSMOPOLITAN_C_END_
+#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
+#endif /* COSMOPOLITAN_LIBC_RUNTIME_GC_H_ */