Initial project import

tools/v/thirdparty/libgc/include/gc.h

@@ -0,0 +1,16 @@
+/* This file is installed for backward compatibility. */
+#include "gc/gc.h"
+
+/* Fix for vlang/v#27179: the original version of this file cast the
+ * pointer argument to V's `u64` type, which makes the header illegal
+ * to include from standalone C (any C shim doing `#include <gc.h>`
+ * via V's -I@VEXEROOT/thirdparty/libgc/include path would fail with
+ * "unknown type: u64"). `GC_word` is the libgc-defined type that
+ * `GC_noop1` actually takes (gc/gc.h, typedef'd to uintptr_t on most
+ * platforms) — using it makes this header valid both from V code and
+ * from plain C shims. */
+#ifndef _MSC_VER
+__attribute__ ((weak)) GC_API void GC_CALL GC_noop1_ptr(volatile void *p) {
+   GC_noop1((GC_word)p);
+}
+#endif