all: fix compilation with -gc boehm_leak (vlang#570)

Co-authored-by: lmp <[email protected]>

c/memory.c.v

@@ -0,0 +1,60 @@
+module c
+
+// When the Boehm collector is used, it is better to replace SDL's memory allocation functions, with versions
+// that Boehm will later know how to process. The callbacks here provide such versions:
+fn cb_malloc_func(size usize) voidptr {
+	res := unsafe { malloc(int(size)) }
+	$if trace_sdl_memory ? {
+		C.fprintf(C.stderr, c'>> sdl.c.cb_malloc_func | size: %lu | => %p\n', size, res)
+	}
+	return res
+}
+
+fn cb_calloc_func(nmemb usize, size usize) voidptr {
+	res := unsafe { vcalloc(isize(nmemb) * isize(size)) }
+	$if trace_sdl_memory ? {
+		C.fprintf(C.stderr, c'>> sdl.c.cb_calloc_func | nmemb: %lu | size: %lu | => %p\n',
+			nmemb, size, res)
+	}
+	return res
+}
+
+fn cb_realloc_func(mem voidptr, size usize) voidptr {
+	res := unsafe { v_realloc(&u8(mem), isize(size)) }
+	$if trace_sdl_memory ? {
+		C.fprintf(C.stderr, c'>> sdl.c.cb_realloc_func | mem: %p | size: %lu | => %p\n',
+			mem, size, res)
+	}
+	return res
+}
+
+fn cb_free_func(mem voidptr) {
+	$if trace_sdl_memory ? {
+		C.fprintf(C.stderr, c'>> sdl.c.cb_free_func | mem: %p\n')
+	}
+	unsafe { free(mem) }
+}
+
+pub type MallocFunc = fn (size usize) voidptr // fn(size usize) voidptr
+
+pub type CallocFunc = fn (nmemb usize, size usize) voidptr // fn(nmemb usize, size usize) voidptr
+
+pub type ReallocFunc = fn (mem voidptr, size usize) voidptr // fn(mem voidptr, size usize) voidptr
+
+pub type FreeFunc = fn (mem voidptr) // fn(mem voidptr)
+
+fn C.SDL_SetMemoryFunctions(malloc_func MallocFunc, calloc_func CallocFunc, realloc_func ReallocFunc, free_func FreeFunc) int
+fn C.SDL_GetNumAllocations() int
+
+fn init() {
+	prev_allocations := C.SDL_GetNumAllocations()
+	if prev_allocations > 0 {
+		eprintln('SDL memory allocation functions should have been replaced with the V ones, but vsdl found, that you did already ${prev_allocations} allocations.')
+		return
+	}
+	replaced := C.SDL_SetMemoryFunctions(cb_malloc_func, cb_calloc_func, cb_realloc_func,
+		cb_free_func)
+	if replaced != 0 {
+		eprintln('SDL memory allocation functions were not replaced.')
+	}
+}

c/sdl.c.v

@@ -34,12 +34,4 @@ $if x64 {
 #flag windows -Dmain=SDL_main
 #flag windows -lSDL2main -lSDL2
 
-$if gcboehm ? {
-	#define SDL_malloc GC_MALLOC
-	#define SDL_calloc(n,m) V_GC_SDL_calloc(n, m)
-	#define SDL_realloc GC_REALLOC
-	#define SDL_free GC_FREE
-	#insert "@VMODROOT/c/v_gc_sdl_boehm.c"
-}
-
 #include <SDL.h>