notmuch integration, using nix flake (nix develop)

build.zig

@@ -3,12 +3,16 @@ const std = @import("std");
 // Although this function looks imperative, note that its job is to
 // declaratively construct a build graph that will be executed by an external
 // runner.
-pub fn build(b: *std.Build) void {
+pub fn build(b: *std.Build) !void {
     // Standard target options allows the person running `zig build` to choose
     // what target to build for. Here we do not override the defaults, which
     // means any target is allowed, and the default is native. Other options
     // for restricting supported target set are available.
-    const target = b.standardTargetOptions(.{});
+    var target_query = b.standardTargetOptionsQueryOnly(.{});
+
+    const paths = try checkNix(b, &target_query);
+    const reload_discovered_native_paths = target_query.dynamic_linker.len != 0;
+    const target = b.resolveTargetQuery(target_query);
 
     // Standard optimization options allow the person running `zig build` to select
     // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall. Here we do not
@@ -35,6 +39,8 @@ pub fn build(b: *std.Build) void {
         .target = target,
         .optimize = optimize,
     });
+
+    configure(exe, paths, reload_discovered_native_paths);
     // This declares intent for the executable to be installed into the
     // standard location when the user invokes the "install" step (the default
     // step when running `zig build`).
@@ -70,6 +76,7 @@ pub fn build(b: *std.Build) void {
         .target = target,
         .optimize = optimize,
     });
+    configure(exe, paths, reload_discovered_native_paths);
 
     const run_lib_unit_tests = b.addRunArtifact(lib_unit_tests);
 
@@ -79,6 +86,7 @@ pub fn build(b: *std.Build) void {
         .optimize = optimize,
     });
 
+    configure(exe_unit_tests, paths, reload_discovered_native_paths);
     const run_exe_unit_tests = b.addRunArtifact(exe_unit_tests);
 
     // Similar to creating the run step earlier, this exposes a `test` step to
@@ -88,3 +96,129 @@ pub fn build(b: *std.Build) void {
     test_step.dependOn(&run_lib_unit_tests.step);
     test_step.dependOn(&run_exe_unit_tests.step);
 }
+
+fn configure(compile: *std.Build.Step.Compile, paths: std.zig.system.NativePaths, reload_paths: bool) void {
+    compile.linkLibC();
+    compile.linkSystemLibrary("notmuch");
+
+    // These are only needed if we are in nix develop shell
+    if (!reload_paths) return;
+    for (paths.lib_dirs.items) |dir|
+        compile.addLibraryPath(.{ .cwd_relative = dir });
+    for (paths.include_dirs.items) |dir|
+        compile.addIncludePath(.{ .cwd_relative = dir });
+    for (paths.rpaths.items) |dir|
+        compile.addRPath(.{ .cwd_relative = dir });
+}
+
+fn checkNix(b: *std.Build, target_query: *std.Target.Query) !std.zig.system.NativePaths {
+    // All linux-specific stuff should be in here
+    if (@import("builtin").os.tag != .linux or !(target_query.os_tag == null or target_query.os_tag.? == .linux)) {
+        std.log.err("Only linux host and target builds supported right now", .{});
+        return error.NotImplemented;
+    }
+    // Capture the natively detected paths for potential future use
+    const native_result = b.resolveTargetQuery(target_query.*);
+    const paths = try std.zig.system.NativePaths.detect(b.allocator, native_result.result);
+    const nix_develop_bintools = std.posix.getenv("NIX_BINTOOLS");
+    if (nix_develop_bintools) |bintools| {
+        // std.debug.print("\nDetected nix bintools\n", .{});
+        // We'll capture the interpreter used in $NIX_BINTOOLS/bin/size
+        // We expect this to be a symlink to a native elf executable
+        // readlink $NIX_BINTOOLS/bin/size
+        var pathbuf: [std.posix.PATH_MAX]u8 = undefined;
+        const elf_path = try std.posix.readlink(
+            try std.fs.path.join(b.allocator, &[_][]const u8{
+                bintools,
+                "bin",
+                "size",
+            }),
+            &pathbuf,
+        );
+
+        // Setting the dynamic linker (necessary to avoid dll hell) will put
+        // zig into a non-native mode, and will therefore ignore all the native
+        // paths. We'll put these back from the values captured above in
+        // our configure function
+        target_query.dynamic_linker = try getDynamicLinker(elf_path);
+    }
+    return paths;
+}
+fn getDynamicLinker(elf_path: []const u8) !std.Target.DynamicLinker {
+    // read the dynamic linker from this
+    const elf_file = try std.fs.openFileAbsolute(elf_path, .{});
+    defer elf_file.close();
+    var file_contents: [1024 * 1024]u8 = undefined; // binary is expected to be appox 40k
+    const read = try elf_file.readAll(&file_contents);
+    if (read == 1024 * 1024) {
+        std.log.err("file too big!", .{});
+        return error.FileTooBig;
+    }
+    if (!std.mem.eql(u8, file_contents[0..4], &[_]u8{ 0x7F, 0x45, 0x4C, 0x46 })) {
+        std.log.err("file not an ELF!", .{});
+        return error.FileNotElf;
+    }
+    if (!std.mem.eql(u8, file_contents[4..9], &[_]u8{ 0x02, 0x01, 0x01, 0x00, 0x00 })) {
+        std.log.err("ELF header not expected (64 bit, LSB, version 1, SYSV ABI, ABI version 0)", .{});
+        std.log.err("It's possible the code will work with unexpected header...might loosen this restriction and see what happens", .{});
+        std.log.err("(32 bit will require code change)", .{});
+        return error.FileNotExpectedElf;
+    }
+    if (file_contents[0x10] != 0x02) {
+        std.log.err("ELF not executable", .{});
+        return error.FileNotExpectedElf;
+    }
+    if (file_contents[0x14] != 0x01) {
+        std.log.err("ELF not version 1", .{});
+        return error.FileNotExpectedElf;
+    }
+    // Section header table
+    const e_shoff = std.mem.littleToNative(u64, @as(*u64, @ptrFromInt(@intFromPtr(file_contents[0x28 .. 0x29 + 8]))).*); // E8 9D 00 00 00 00 00 00
+    // Number of sections
+    const e_shnum = std.mem.littleToNative(u16, @as(*u16, @ptrFromInt(@intFromPtr(file_contents[0x3c .. 0x3d + 2]))).*); // 1d
+
+    // Index of section header that contains section header names
+    const e_shstrndx = std.mem.littleToNative(u16, @as(*u16, @ptrFromInt(@intFromPtr(file_contents[0x3e .. 0x3f + 2]))).*); // 1c
+    // Beginning of section 0x1c (28) that contains header names
+    const e_shstroff = e_shoff + (64 * e_shstrndx); // 0xa4e8
+    const shstrtab_contents = file_contents[e_shstroff .. e_shstroff + 1 + (e_shnum * 64)];
+    // Offset for my set of null terminated strings
+    const shstrtab_sh_offset = std.mem.littleToNative(u64, @as(*u64, @ptrFromInt(@intFromPtr(shstrtab_contents[0x18 .. 0x19 + 8]))).*); // 0x9cec
+    // Total size of section
+    const shstrtab_sh_size = std.mem.littleToNative(u64, @as(*u64, @ptrFromInt(@intFromPtr(shstrtab_contents[0x20 .. 0x21 + 8]))).*); // 250
+    // std.debug.print("e_shoff: {x}, e_shstrndx: {x}, e_shstroff: {x}, e_shnum: {x}, shstrtab_sh_offset: {x}, shstrtab_sh_size: {}\n", .{ e_shoff, e_shstrndx, e_shstroff, e_shnum, shstrtab_sh_offset, shstrtab_sh_size });
+    const shstrtab_strings = file_contents[shstrtab_sh_offset .. shstrtab_sh_offset + 1 + shstrtab_sh_size];
+    var interp: ?[]const u8 = null;
+    for (0..e_shnum) |shndx| {
+        // get section offset. Look for type == SHT_PROGBITS, then go fetch name
+        const sh_off = e_shoff + (64 * shndx);
+        const sh_contents = file_contents[sh_off .. sh_off + 1 + 64];
+        const sh_type = std.mem.littleToNative(u16, @as(*u16, @ptrFromInt(@intFromPtr(sh_contents[0x04 .. 0x05 + 2]))).*);
+        if (sh_type != 0x01) continue;
+        // This is an offset to the null terminated string in our string content
+        const sh_name_offset = std.mem.littleToNative(u16, @as(*u16, @ptrFromInt(@intFromPtr(sh_contents[0x00 .. 0x01 + 2]))).*);
+        const sentinel = std.mem.indexOfScalar(u8, shstrtab_strings[sh_name_offset..], 0);
+        if (sentinel == null) {
+            std.log.err("Invalid ELF file", .{});
+            return error.InvalidElfFile;
+        }
+        const sh_name = shstrtab_strings[sh_name_offset .. sh_name_offset + sentinel.?];
+        // std.debug.print("section name: {s}\n", .{sh_name});
+        if (std.mem.eql(u8, ".interp", sh_name)) {
+            // found interpreter
+            const interp_offset = std.mem.littleToNative(u64, @as(*u64, @ptrFromInt(@intFromPtr(sh_contents[0x18 .. 0x19 + 8]))).*); // 0x9218
+            const interp_size = std.mem.littleToNative(u64, @as(*u64, @ptrFromInt(@intFromPtr(sh_contents[0x20 .. 0x21 + 8]))).*); // 2772
+            // std.debug.print("Found interpreter at {x}, size: {}\n", .{ interp_offset, interp_size });
+            interp = file_contents[interp_offset .. interp_offset + 1 + interp_size];
+            // std.debug.print("Interp: {s}\n", .{interp});
+        }
+    }
+    if (interp == null) {
+        std.log.err("Could not locate interpreter", .{});
+        return error.CouldNotLocateInterpreter;
+    }
+
+    var dl = std.Target.DynamicLinker{ .buffer = undefined, .len = 0 };
+    dl.set(interp);
+    return dl;
+}

src/main.zig

@@ -1,8 +1,11 @@
 const std = @import("std");
+const c = @cImport({
+    @cInclude("notmuch.h");
+});
 
 pub fn main() !void {
     // Prints to stderr (it's a shortcut based on `std.io.getStdErr()`)
-    std.debug.print("All your {s} are belong to us.\n", .{"codebase"});
+    std.debug.print("All your {s} are belong to us. Status: {s}\n", .{ "codebase", c.notmuch_status_to_string(0) });
 
     // stdout is for the actual output of your application, for example if you
     // are implementing gzip, then only the compressed bytes should be sent to
@@ -16,9 +19,6 @@ pub fn main() !void {
     try bw.flush(); // don't forget to flush!
 }
 
-test "simple test" {
+test "can get status" {
-    var list = std.ArrayList(i32).init(std.testing.allocator);
+    try std.testing.expectEqualStrings("No error occurred", std.mem.span(c.notmuch_status_to_string(0)));
-    defer list.deinit(); // try commenting this out and see if zig detects the memory leak!
-    try list.append(42);
-    try std.testing.expectEqual(@as(i32, 42), list.pop());
 }