all: fix CI failures from VGC PR - add missing stubs, fix README

Author: medvednikov

vlib/builtin/builtin_d_vgc.c.v

@@ -1,7 +1,5 @@
 // builtin_d_vgc.c.v - V Garbage Collector additional support
-// Conditionally compiled when -gc vgc is used.
-// The public gc_* API is provided by builtin_notd_gcboehm.c.v (which delegates
-// to VGC via $if vgc ? blocks) to avoid duplicate function definitions.
+// Conditionally compiled when -d vgc is used.
 // The gc_heap_usage/gc_memory_use functions are in allocation.c.v with $if vgc ? branches.
 
 module builtin

vlib/builtin/builtin_notd_gcboehm.c.v

@@ -24,38 +24,32 @@ fn C.GC_get_memory_use() usize
 fn C.GC_gcollect()
 
 // gc_check_leaks is useful for detecting leaks, but it needs the GC to run.
-// When GC is not used, it is a NOP. When VGC is active, delegates to vgc.
+// When GC is not used, it is a NOP.
 pub fn gc_check_leaks() {}
 
 // gc_is_enabled() returns true, if the GC is enabled at runtime.
-// With `-gc none` returns false. With `-gc vgc` delegates to the VGC.
+// It will always return false, with `-gc none`.
+// See also gc_disable() and gc_enable().
 pub fn gc_is_enabled() bool {
-	$if vgc ? {
-		return C.vgc_atomic_load_u32(unsafe { &vgc_heap.gc_enabled }) != 0
-	}
 	return false
 }
 
 // gc_enable explicitly enables the GC.
-pub fn gc_enable() {
-	$if vgc ? {
-		C.vgc_atomic_store_u32(unsafe { &vgc_heap.gc_enabled }, 1)
-	}
-}
+// Note, that garbage collections are done automatically, when needed in most cases,
+// and also that by default the GC is on, so you do not need to enable it.
+// See also gc_disable() and gc_collect().
+// Note that gc_enable() is a NOP with `-gc none`.
+pub fn gc_enable() {}
 
 // gc_disable explicitly disables the GC.
-pub fn gc_disable() {
-	$if vgc ? {
-		C.vgc_atomic_store_u32(unsafe { &vgc_heap.gc_enabled }, 0)
-	}
-}
+// Do not forget to enable it again by calling gc_enable(), when your program is otherwise idle, and can afford it.
+// See also gc_enable() and gc_collect().
+// Note that gc_disable() is a NOP with `-gc none`.
+pub fn gc_disable() {}
 
 // gc_collect explicitly performs a garbage collection.
-pub fn gc_collect() {
-	$if vgc ? {
-		vgc_gc_start()
-	}
-}
+// When the GC is not on, (with `-gc none`), it is a NOP.
+pub fn gc_collect() {}
 
 pub type FnGC_WarnCB = fn (msg &char, arg usize)
 

vlib/builtin/vgc_notd_vgc.c.v

@@ -0,0 +1,32 @@
+module builtin
+
+// Stub declarations for VGC functions, so that V does not error
+// because of the missing definitions in $if vgc ? { } blocks.
+// Note: they will NOT be called, since calls to them are wrapped with `$if vgc ? { }`.
+
+fn vgc_malloc(n usize) voidptr {
+	return unsafe { nil }
+}
+
+fn vgc_malloc_noscan(n usize) voidptr {
+	return unsafe { nil }
+}
+
+fn vgc_realloc(old_ptr voidptr, new_size usize) voidptr {
+	return unsafe { nil }
+}
+
+fn vgc_calloc(n usize) voidptr {
+	return unsafe { nil }
+}
+
+fn vgc_free(ptr voidptr) {
+}
+
+fn vgc_heap_usage() (usize, usize, usize, usize, usize) {
+	return 0, 0, 0, 0, 0
+}
+
+fn vgc_memory_use() usize {
+	return 0
+}

vlib/goroutines/README.md

@@ -1,10 +1,14 @@
 # goroutines
 
-Go-style goroutine runtime for V, implementing the GMP (Goroutine-Machine-Processor) scheduling model translated from the Go runtime (`src/runtime/proc.go`, `runtime2.go`, `chan.go`).
+Go-style goroutine runtime for V, implementing the GMP
+(Goroutine-Machine-Processor) scheduling model translated
+from the Go runtime (`src/runtime/proc.go`, `runtime2.go`,
+`chan.go`).
 
 ## Overview
 
-This module provides lightweight goroutines for V's `go` keyword, as opposed to `spawn` which creates OS threads.
+This module provides lightweight goroutines for V's `go`
+keyword, as opposed to `spawn` which creates OS threads.
 
 ### GMP Model
 
@@ -22,7 +26,7 @@ This module provides lightweight goroutines for V's `go` keyword, as opposed to
 
 ## Usage
 
-```v
+```v ignore
 // `go` launches a goroutine (lightweight, scheduled by GMP)
 go expensive_computation()