glue mimalloc with netsurf C libs

build.zig

@@ -152,6 +152,10 @@ fn common(
 ) !void {
     try jsruntime_pkgs.add(step, options);
     linkNetSurf(step);
+
+    // link mimalloc
+    step.addObjectFile(.{ .path = "vendor/mimalloc/out/libmimalloc.a" });
+    step.addIncludePath(.{ .path = "vendor/mimalloc/include" });
 }
 
 fn linkNetSurf(step: *std.build.LibExeObjStep) void {

src/mimalloc.zig

@@ -0,0 +1,48 @@
+// This file makes the glue between mimalloc heap allocation and libdom memory
+// management.
+// We replace the libdom default usage of allocations with mimalloc heap
+// allocation to be able to free all memory used at once, like an arena usage.
+
+const std = @import("std");
+const c = @cImport({
+    @cInclude("mimalloc.h");
+});
+
+const Error = error{
+    HeapNotNull,
+    HeapNull,
+};
+
+var heap: ?*c.mi_heap_t = null;
+
+pub fn create() Error!void {
+    if (heap != null) return Error.HeapNotNull;
+    heap = c.mi_heap_new();
+    if (heap == null) return Error.HeapNull;
+}
+
+pub fn destroy() void {
+    if (heap == null) return;
+    c.mi_heap_destroy(heap.?);
+    heap = null;
+}
+
+pub export fn m_alloc(size: usize) callconv(.C) ?*anyopaque {
+    if (heap == null) return null;
+    return c.mi_heap_malloc(heap.?, size);
+}
+
+pub export fn re_alloc(ptr: ?*anyopaque, size: usize) callconv(.C) ?*anyopaque {
+    if (heap == null) return null;
+    return c.mi_heap_realloc(heap.?, ptr, size);
+}
+
+pub export fn c_alloc(nmemb: usize, size: usize) callconv(.C) ?*anyopaque {
+    if (heap == null) return null;
+    return c.mi_heap_calloc(heap.?, nmemb, size);
+}
+
+// NOOP, use destroy to clear all the memory allocated at once.
+pub export fn f_ree(_: ?*anyopaque) callconv(.C) void {
+    return;
+}

src/netsurf.zig

@@ -8,9 +8,29 @@ const c = @cImport({
     @cInclude("events/event.h");
 });
 
+const mimalloc = @import("mimalloc.zig");
+
 const Callback = @import("jsruntime").Callback;
 const EventToInterface = @import("events/event.zig").Event.toInterface;
 
+// init initializes netsurf lib.
+// init starts a mimalloc heap arena for the netsurf session. The caller must
+// call deinit() to free the arena memory.
+pub fn init() !void {
+    try mimalloc.create();
+}
+
+// deinit frees the mimalloc heap arena memory.
+// It also clean dom namespaces and lwc strings.
+pub fn deinit() void {
+    _ = c.dom_namespace_finalise();
+
+    // destroy all lwc strings.
+    c.lwc_deinit_strings();
+
+    mimalloc.destroy();
+}
+
 // Vtable
 // ------