Initial project import

tools/v/vlib/goroutines/context_nix.h

@@ -0,0 +1,69 @@
+#ifndef GOROUTINES_CONTEXT_NIX_H
+#define GOROUTINES_CONTEXT_NIX_H
+
+#include <ucontext.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+// Extended context: ucontext_t + entry function info for first-time starts.
+typedef struct {
+    ucontext_t uctx;
+    void (*entry_fn)(void *);
+    void *entry_arg;
+} goroutine_ctx_t;
+
+// Thread-local pointer to the target goroutine context.
+// Set just before swapcontext/setcontext so the trampoline can find its fn/arg.
+#if defined(_WIN32) || defined(_WIN64)
+static __declspec(thread) goroutine_ctx_t *_goroutine_start_ctx = NULL;
+#else
+static _Thread_local goroutine_ctx_t *_goroutine_start_ctx = NULL;
+#endif
+
+static void *goroutines_context_alloc(void) {
+    return calloc(1, sizeof(goroutine_ctx_t));
+}
+
+// Zero-argument trampoline. Reads fn/arg from the TLS-stored context.
+// This avoids passing arguments through makecontext, which is broken on macOS ARM64.
+static void goroutines__context_trampoline(void) {
+    goroutine_ctx_t *gctx = _goroutine_start_ctx;
+    _goroutine_start_ctx = NULL;
+    void (*fn)(void *) = gctx->entry_fn;
+    void *arg = gctx->entry_arg;
+    // Clear so future context switches to this goroutine don't re-trigger
+    gctx->entry_fn = NULL;
+    gctx->entry_arg = NULL;
+    fn(arg);
+}
+
+static void goroutines_context_init(void *ctx_buf, void *stack, int stack_size, void *entry_fn, void *arg) {
+    goroutine_ctx_t *gctx = (goroutine_ctx_t *)ctx_buf;
+    gctx->entry_fn = (void (*)(void *))entry_fn;
+    gctx->entry_arg = arg;
+    getcontext(&gctx->uctx);
+    gctx->uctx.uc_stack.ss_sp = stack;
+    gctx->uctx.uc_stack.ss_size = (size_t)stack_size;
+    gctx->uctx.uc_link = NULL;
+    makecontext(&gctx->uctx, (void (*)())goroutines__context_trampoline, 0);
+}
+
+static void goroutines_context_switch(void *from_buf, void *to_buf) {
+    goroutine_ctx_t *from = (goroutine_ctx_t *)from_buf;
+    goroutine_ctx_t *to = (goroutine_ctx_t *)to_buf;
+    // If switching to a goroutine that hasn't started yet, set TLS for trampoline
+    if (to->entry_fn != NULL) {
+        _goroutine_start_ctx = to;
+    }
+    swapcontext(&from->uctx, &to->uctx);
+}
+
+static void goroutines_context_set(void *to_buf) {
+    goroutine_ctx_t *to = (goroutine_ctx_t *)to_buf;
+    if (to->entry_fn != NULL) {
+        _goroutine_start_ctx = to;
+    }
+    setcontext(&to->uctx);
+}
+
+#endif