feat(libstore): add page size system feature

src/libstore/globals.cc

@@ -175,6 +175,8 @@ static bool hasVirt() {
 }
 #endif
 
+extern "C" const char** nix_libstore_get_default_system_features();
+
 StringSet Settings::getDefaultSystemFeatures()
 {
     /* For backwards compatibility, accept some "features" that are
@@ -196,6 +198,14 @@ StringSet Settings::getDefaultSystemFeatures()
         features.insert("apple-virt");
     #endif
 
+    const char** value = nix_libstore_get_default_system_features();
+    if (value != nullptr) {
+        for (size_t i = 0; value[i] != nullptr; i++) {
+            features.insert(value[i]);
+        }
+    }
+    free(value);
+
     return features;
 }
 

src/libstore/globals.zig

@@ -0,0 +1,23 @@
+const std = @import("std");
+
+pub fn getDefaultSystemFeatures() callconv(.C) ?[*:null]const ?[*:0]const u8 {
+    var list = std.ArrayList(?[*:0]const u8).init(std.heap.c_allocator);
+    defer list.deinit();
+
+    const pgsize = std.heap.pageSize();
+
+    if (pgsize == std.heap.page_size_max) {
+        list.append(std.fmt.allocPrintZ(std.heap.c_allocator, "pages-{d}k", .{pgsize / 1024}) catch return null) catch return null;
+    } else {
+        var i = pgsize;
+        while (i < std.heap.page_size_max) : (i *= 2) {
+            list.append(std.fmt.allocPrintZ(std.heap.c_allocator, "pages-{d}k", .{i / 1024}) catch return null) catch return null;
+        }
+    }
+
+    return list.toOwnedSliceSentinel(null) catch return null;
+}
+
+comptime {
+    @export(&getDefaultSystemFeatures, .{ .name = "nix_libstore_get_default_system_features" });
+}

src/libstore/libstore.zig

@@ -0,0 +1,5 @@
+pub const globals = @import("globals.zig");
+
+comptime {
+    _ = globals;
+}

src/libstore/meson.build

@@ -1,4 +1,4 @@
-project('nix-store', 'cpp',
+project('nix-store', 'cpp', 'c',
   version : files('.zix-version'),
   default_options : [
     'cpp_std=c++2a',
@@ -132,6 +132,8 @@ if aws_s3.found()
 endif
 deps_other += aws_s3
 
+subdir('nix-meson-build-support/zig')
+
 subdir('nix-meson-build-support/generate-header')
 
 generated_headers = []
@@ -420,6 +422,18 @@ endforeach
 subdir('nix-meson-build-support/export-all-symbols')
 subdir('nix-meson-build-support/windows-version')
 
+sources += custom_target(
+  'zig build-lib',
+  command: [zig, 'build-lib', '-femit-h=@OUTDIR@/libstore-zig.h', '-femit-bin=@OUTPUT@', '-ofmt=c', '-lc', zig_args, '@INPUT@'],
+  output: 'libstore-zig.c',
+  input: 'libstore.zig',
+  depend_files: [
+    'globals.zig',
+  ],
+)
+
+include_dirs += fs.parent(fs.parent(zig.full_path())) / 'lib' / 'zig'
+
 this_library = library(
   'nixstore',
   generated_headers,

src/libstore/package.nix

@@ -50,6 +50,7 @@ mkMesonLibrary (finalAttrs: {
     (fileset.fileFilter (file: file.hasExt "sb") ./.)
     (fileset.fileFilter (file: file.hasExt "md") ./.)
     (fileset.fileFilter (file: file.hasExt "sql") ./.)
+    (fileset.fileFilter (file: file.hasExt "zig") ./.)
   ];
 
   nativeBuildInputs = lib.optional embeddedSandboxShell unixtools.hexdump;