diff --git a/CMakeLists.txt b/CMakeLists.txt
index 86dca3aea5..8b119e1628 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -199,6 +199,7 @@ install(FILES ${C_HEADERS} DESTINATION ${C_HEADERS_DEST})
 install(FILES "${CMAKE_SOURCE_DIR}/std/base64.zig" DESTINATION "${ZIG_STD_DEST}")
 install(FILES "${CMAKE_SOURCE_DIR}/std/buf_map.zig" DESTINATION "${ZIG_STD_DEST}")
 install(FILES "${CMAKE_SOURCE_DIR}/std/buf_set.zig" DESTINATION "${ZIG_STD_DEST}")
+install(FILES "${CMAKE_SOURCE_DIR}/std/buffer.zig" DESTINATION "${ZIG_STD_DEST}")
 install(FILES "${CMAKE_SOURCE_DIR}/std/build.zig" DESTINATION "${ZIG_STD_DEST}")
 install(FILES "${CMAKE_SOURCE_DIR}/std/c/darwin.zig" DESTINATION "${ZIG_STD_DEST}/c")
 install(FILES "${CMAKE_SOURCE_DIR}/std/c/index.zig" DESTINATION "${ZIG_STD_DEST}/c")
diff --git a/example/shared_library/build.zig b/example/shared_library/build.zig
new file mode 100644
index 0000000000..1212c58ab8
--- /dev/null
+++ b/example/shared_library/build.zig
@@ -0,0 +1,20 @@
+const Builder = @import("std").build.Builder;
+
+pub fn build(b: &Builder) {
+    const lib = b.addSharedLibrary("mathtest", "mathtest.zig", b.version(1, 0, 0));
+
+    const exe = b.addCExecutable("test");
+    exe.addCompileFlags([][]const u8 {
+        "-std=c99",
+    });
+    exe.addSourceFile("test.c");
+    exe.linkLibrary(lib);
+
+    b.default_step.dependOn(&exe.step);
+
+    const run_cmd = b.addCommand(b.out_dir, b.env_map, "./test", [][]const u8{});
+    run_cmd.step.dependOn(&exe.step);
+
+    const test_step = b.step("test", "Test the program");
+    test_step.dependOn(&run_cmd.step);
+}
diff --git a/example/shared_library/mathtest.zig b/example/shared_library/mathtest.zig
index 9dc33b9555..a11642554f 100644
--- a/example/shared_library/mathtest.zig
+++ b/example/shared_library/mathtest.zig
@@ -1,7 +1,3 @@
 export fn add(a: i32, b: i32) -> i32 {
     a + b
 }
-
-export fn hang() -> unreachable {
-    while (true) { }
-}
diff --git a/example/shared_library/test.c b/example/shared_library/test.c
index 4fff250f08..b60a6a5a75 100644
--- a/example/shared_library/test.c
+++ b/example/shared_library/test.c
@@ -1,7 +1,7 @@
 #include "mathtest.h"
-#include <stdio.h>
+#include <assert.h>
 
 int main(int argc, char **argv) {
-    printf("%d\n", add(42, 1137));
+    assert(add(42, 1337) == 1379);
     return 0;
 }
diff --git a/src/codegen.cpp b/src/codegen.cpp
index 735c3f19a9..d8c3e0e2d6 100644
--- a/src/codegen.cpp
+++ b/src/codegen.cpp
@@ -155,6 +155,12 @@ void codegen_set_test_name_prefix(CodeGen *g, Buf *prefix) {
     g->test_name_prefix = prefix;
 }
 
+void codegen_set_lib_version(CodeGen *g, size_t major, size_t minor, size_t patch) {
+    g->version_major = major;
+    g->version_minor = minor;
+    g->version_patch = patch;
+}
+
 void codegen_set_is_test(CodeGen *g, bool is_test_build) {
     g->is_test_build = is_test_build;
 }
diff --git a/src/codegen.hpp b/src/codegen.hpp
index 03aa6f53e4..d5d7bd0644 100644
--- a/src/codegen.hpp
+++ b/src/codegen.hpp
@@ -46,6 +46,7 @@ void codegen_set_linker_script(CodeGen *g, const char *linker_script);
 void codegen_set_omit_zigrt(CodeGen *g, bool omit_zigrt);
 void codegen_set_test_filter(CodeGen *g, Buf *filter);
 void codegen_set_test_name_prefix(CodeGen *g, Buf *prefix);
+void codegen_set_lib_version(CodeGen *g, size_t major, size_t minor, size_t patch);
 
 PackageTableEntry *new_package(const char *root_src_dir, const char *root_src_path);
 void codegen_add_root_code(CodeGen *g, Buf *source_dir, Buf *source_basename, Buf *source_code);
diff --git a/src/main.cpp b/src/main.cpp
index 1d37352427..bf2dbcf683 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -67,6 +67,10 @@ static int usage(const char *arg0) {
         "Test Options:\n"
         "  --test-filter [text]         skip tests that do not match filter\n"
         "  --test-name-prefix [text]    add prefix to all tests\n"
+        "Dynamic Library Options:\n"
+        "  --ver-major [ver]            semver major version\n"
+        "  --ver-minor [ver]            semver minor version\n"
+        "  --ver-patch [ver]            semver patch version\n"
     , arg0);
     return EXIT_FAILURE;
 }
@@ -156,6 +160,9 @@ int main(int argc, char **argv) {
     ZigList<const char *> objects = {0};
     const char *test_filter = nullptr;
     const char *test_name_prefix = nullptr;
+    size_t ver_major = 0;
+    size_t ver_minor = 0;
+    size_t ver_patch = 0;
 
     if (argc >= 2 && strcmp(argv[1], "build") == 0) {
         const char *zig_exe_path = arg0;
@@ -350,6 +357,12 @@ int main(int argc, char **argv) {
                     test_filter = argv[i];
                 } else if (strcmp(arg, "--test-name-prefix") == 0) {
                     test_name_prefix = argv[i];
+                } else if (strcmp(arg, "--ver-major") == 0) {
+                    ver_major = atoi(argv[i]);
+                } else if (strcmp(arg, "--ver-minor") == 0) {
+                    ver_minor = atoi(argv[i]);
+                } else if (strcmp(arg, "--ver-patch") == 0) {
+                    ver_patch = atoi(argv[i]);
                 } else {
                     fprintf(stderr, "Invalid argument: %s\n", arg);
                     return usage(arg0);
@@ -509,6 +522,7 @@ int main(int argc, char **argv) {
             }
 
             CodeGen *g = codegen_create(&root_source_dir, target);
+            codegen_set_lib_version(g, ver_major, ver_minor, ver_patch);
             codegen_set_is_release(g, is_release_build);
             codegen_set_is_test(g, cmd == CmdTest);
             codegen_set_linker_script(g, linker_script);
diff --git a/std/buffer.zig b/std/buffer.zig
new file mode 100644
index 0000000000..c7f0861356
--- /dev/null
+++ b/std/buffer.zig
@@ -0,0 +1,117 @@
+const debug = @import("debug.zig");
+const mem = @import("mem.zig");
+const Allocator = mem.Allocator;
+const assert = debug.assert;
+const List = @import("list.zig").List;
+
+/// A buffer that allocates memory and maintains a null byte at the end.
+pub const Buffer = struct {
+    list: List(u8),
+
+    /// Must deinitialize with deinit.
+    pub fn init(allocator: &Allocator, m: []const u8) -> %Buffer {
+        var self = %return initSize(allocator, m.len);
+        mem.copy(u8, self.list.items, m);
+        return self;
+    }
+
+    /// Must deinitialize with deinit.
+    pub fn initSize(allocator: &Allocator, size: usize) -> %Buffer {
+        var self = initNull(allocator);
+        %return self.resize(size);
+        return self;
+    }
+
+    /// Must deinitialize with deinit.
+    /// None of the other operations are valid until you do one of these:
+    /// * ::replaceContents
+    /// * ::replaceContentsBuffer
+    /// * ::resize
+    pub fn initNull(allocator: &Allocator) -> Buffer {
+        Buffer {
+            .list = List(u8).init(allocator),
+        }
+    }
+
+    /// Must deinitialize with deinit.
+    pub fn initFromBuffer(buffer: &const Buffer) -> %Buffer {
+        return Buffer.init(buffer.list.allocator, buffer.toSliceConst());
+    }
+
+    pub fn deinit(self: &Buffer) {
+        self.list.deinit();
+    }
+
+    pub fn toSlice(self: &Buffer) -> []u8 {
+        return self.list.toSlice()[0...self.len()];
+    }
+
+    pub fn toSliceConst(self: &const Buffer) -> []const u8 {
+        return self.list.toSliceConst()[0...self.len()];
+    }
+
+    pub fn resize(self: &Buffer, new_len: usize) -> %void {
+        %return self.list.resize(new_len + 1);
+        self.list.items[self.len()] = 0;
+    }
+
+    pub fn isNull(self: &const Buffer) -> bool {
+        return self.list.len == 0;
+    }
+
+    pub fn len(self: &const Buffer) -> usize {
+        return self.list.len - 1;
+    }
+
+    pub fn append(self: &Buffer, m: []const u8) -> %void {
+        const old_len = self.len();
+        %return self.resize(old_len + m.len);
+        mem.copy(u8, self.list.toSlice()[old_len...], m);
+    }
+
+    pub fn appendByte(self: &Buffer, byte: u8) -> %void {
+        %return self.resize(self.len() + 1);
+        self.list.items[self.len() - 1] = byte;
+    }
+
+    pub fn eql(self: &const Buffer, m: []const u8) -> bool {
+        mem.eql(u8, self.toSliceConst(), m)
+    }
+
+    pub fn startsWith(self: &const Buffer, m: []const u8) -> bool {
+        if (self.len() < m.len) return false;
+        return mem.eql(u8, self.list.items[0...m.len], m);
+    }
+
+    pub fn endsWith(self: &const Buffer, m: []const u8) -> bool {
+        const l = self.len();
+        if (l < m.len) return false;
+        const start = l - m.len;
+        return mem.eql(u8, self.list.items[start...], m);
+    }
+
+    pub fn replaceContents(self: &const Buffer, m: []const u8) -> %void {
+        %return self.resize(m.len);
+        mem.copy(u8, self.list.toSlice(), m);
+    }
+};
+
+test "simple Buffer" {
+    const cstr = @import("cstr.zig");
+
+    var buf = %%Buffer.init(&debug.global_allocator, "");
+    assert(buf.len() == 0);
+    %%buf.append("hello");
+    %%buf.appendByte(' ');
+    %%buf.append("world");
+    assert(buf.eql("hello world"));
+    assert(mem.eql(u8, cstr.toSliceConst(buf.toSliceConst().ptr), buf.toSliceConst()));
+
+    var buf2 = %%Buffer.initFromBuffer(&buf);
+    assert(buf.eql(buf2.toSliceConst()));
+
+    assert(buf.startsWith("hell"));
+
+    %%buf2.resize(4);
+    assert(buf.startsWith(buf2.toSliceConst()));
+}
diff --git a/std/build.zig b/std/build.zig
index d22d6b660a..29b3350292 100644
--- a/std/build.zig
+++ b/std/build.zig
@@ -120,12 +120,30 @@ pub const Builder = struct {
         self.lib_dir = %%os.path.join(self.allocator, self.prefix, "lib");
     }
 
-    pub fn addExecutable(self: &Builder, name: []const u8, root_src: []const u8) -> &Exe {
-        const exe = %%self.allocator.create(Exe);
-        *exe = Exe.init(self, name, root_src);
+    pub fn addExecutable(self: &Builder, name: []const u8, root_src: []const u8) -> &LibOrExeStep {
+        const exe = %%self.allocator.create(LibOrExeStep);
+        *exe = LibOrExeStep.initExecutable(self, name, root_src);
         return exe;
     }
 
+    pub fn addObject(self: &Builder, name: []const u8, root_src: []const u8) -> &ObjectStep {
+        const obj_step = %%self.allocator.create(ObjectStep);
+        *obj_step = ObjectStep.init(self, name, src);
+        return obj_step;
+    }
+
+    pub fn addSharedLibrary(self: &Builder, name: []const u8, root_src: []const u8, ver: &const Version) -> &LibOrExeStep {
+        const lib_step = %%self.allocator.create(LibOrExeStep);
+        *lib_step = LibOrExeStep.initSharedLibrary(self, name, root_src, ver);
+        return lib_step;
+    }
+
+    pub fn addStaticLibrary(self: &Builder, name: []const u8, root_src: []const u8) -> &LibOrExeStep {
+        const lib_step = %%self.allocator.create(LibOrExeStep);
+        *lib_step = LibOrExeStep.initStaticLibrary(self, name, root_src);
+        return lib_step;
+    }
+
     pub fn addTest(self: &Builder, root_src: []const u8) -> &TestStep {
         const test_step = %%self.allocator.create(TestStep);
         *test_step = TestStep.init(self, root_src);
@@ -487,11 +505,13 @@ pub const Builder = struct {
         return self.invalid_user_input;
     }
 
-    fn spawnChild(self: &Builder, exe_path: []const u8, args: []const []const u8) {
+    fn spawnChild(self: &Builder, exe_path: []const u8, args: []const []const u8) -> %void {
         return self.spawnChildEnvMap(&self.env_map, exe_path, args);
     }
 
-    fn spawnChildEnvMap(self: &Builder, env_map: &const BufMap, exe_path: []const u8, args: []const []const u8) {
+    fn spawnChildEnvMap(self: &Builder, env_map: &const BufMap, exe_path: []const u8,
+        args: []const []const u8) -> %void
+    {
         if (self.verbose) {
             %%io.stderr.printf("{}", exe_path);
             for (args) |arg| {
@@ -501,18 +521,26 @@ pub const Builder = struct {
         }
 
         var child = os.ChildProcess.spawn(exe_path, args, env_map,
-            StdIo.Ignore, StdIo.Inherit, StdIo.Inherit, self.allocator)
-            %% |err| debug.panic("Unable to spawn {}: {}\n", exe_path, @errorName(err));
+            StdIo.Ignore, StdIo.Inherit, StdIo.Inherit, self.allocator) %% |err|
+        {
+            %%io.stderr.printf("Unable to spawn {}: {}\n", exe_path, @errorName(err));
+            return err;
+        };
 
-        const term = %%child.wait();
+        const term = child.wait() %% |err| {
+            %%io.stderr.printf("Unable to spawn {}: {}\n", exe_path, @errorName(err));
+            return err;
+        };
         switch (term) {
             Term.Clean => |code| {
                 if (code != 0) {
-                    debug.panic("Process {} exited with error code {}\n", exe_path, code);
+                    %%io.stderr.printf("Process {} exited with error code {}\n", exe_path, code);
+                    return error.UncleanExit;
                 }
             },
             else => {
-                debug.panic("Process {} terminated unexpectedly\n", exe_path);
+                %%io.stderr.printf("Process {} terminated unexpectedly\n", exe_path);
+                return error.UncleanExit;
             },
         };
 
@@ -547,7 +575,7 @@ pub const Builder = struct {
     }
 
     fn pathFromRoot(self: &Builder, rel_path: []const u8) -> []u8 {
-        return %%os.path.join(self.allocator, self.build_root, rel_path);
+        return %%os.path.resolve(self.allocator, self.build_root, rel_path);
     }
 
     pub fn fmt(self: &Builder, comptime format: []const u8, args: ...) -> []u8 {
@@ -600,7 +628,7 @@ const LinkerScript = enum {
     Path: []const u8,
 };
 
-pub const Exe = struct {
+pub const LibOrExeStep = struct {
     step: Step,
     builder: &Builder,
     root_src: []const u8,
@@ -610,13 +638,42 @@ pub const Exe = struct {
     link_libs: BufSet,
     verbose: bool,
     release: bool,
+    static: bool,
     output_path: ?[]const u8,
+    kind: Kind,
+    version: Version,
+    out_filename: []const u8,
+    out_filename_major_only: []const u8,
+    out_filename_name_only: []const u8,
 
-    pub fn init(builder: &Builder, name: []const u8, root_src: []const u8) -> Exe {
-        Exe {
+    const Kind = enum {
+        Exe,
+        Lib,
+    };
+
+    pub fn initExecutable(builder: &Builder, name: []const u8, root_src: []const u8) -> LibOrExeStep {
+        return initExtraArgs(builder, name, root_src, Kind.Exe, false, builder.version(0, 0, 0));
+    }
+
+    pub fn initSharedLibrary(builder: &Builder, name: []const u8, root_src: []const u8,
+        ver: &const Version) -> LibOrExeStep
+    {
+        return initExtraArgs(builder, name, root_src, Kind.Lib, false, ver);
+    }
+
+    pub fn initStaticLibrary(builder: &Builder, name: []const u8, root_src: []const u8) -> LibOrExeStep {
+        return initExtraArgs(builder, name, root_src, Kind.Lib, true, builder.version(0, 0, 0));
+    }
+
+    fn initExtraArgs(builder: &Builder, name: []const u8, root_src: []const u8, kind: Kind,
+        static: bool, ver: &const Version) -> LibOrExeStep
+    {
+        var self = LibOrExeStep {
             .builder = builder,
             .verbose = false,
             .release = false,
+            .static = static,
+            .kind = kind,
             .root_src = root_src,
             .name = name,
             .target = Target.Native,
@@ -624,14 +681,34 @@ pub const Exe = struct {
             .link_libs = BufSet.init(builder.allocator),
             .step = Step.init(name, builder.allocator, make),
             .output_path = null,
+            .version = *ver,
+            .out_filename = undefined,
+            .out_filename_major_only = undefined,
+            .out_filename_name_only = undefined,
+        };
+        self.computeOutFileNames();
+        return self;
+    }
+
+    fn computeOutFileNames(self: &LibOrExeStep) {
+        switch (self.kind) {
+            Kind.Exe => {
+                self.out_filename = self.builder.fmt("{}{}", self.name, self.target.exeFileExt());
+            },
+            Kind.Lib => {
+                if (self.static) {
+                    self.out_filename = self.builder.fmt("lib{}.a", self.name);
+                } else {
+                    self.out_filename = self.builder.fmt("lib{}.so.{d}.{d}.{d}",
+                        self.name, self.version.major, self.version.minor, self.version.patch);
+                    self.out_filename_major_only = self.builder.fmt("lib{}.so.{d}", self.name, self.version.major);
+                    self.out_filename_name_only = self.builder.fmt("lib{}.so", self.name);
+                }
+            },
         }
     }
 
-    pub fn deinit(self: &Exe) {
-        self.link_libs.deinit();
-    }
-
-    pub fn setTarget(self: &Exe, target_arch: Arch, target_os: Os, target_environ: Environ) {
+    pub fn setTarget(self: &LibOrExeStep, target_arch: Arch, target_os: Os, target_environ: Environ) {
         self.target = Target.Cross {
             CrossTarget {
                 .arch = target_arch,
@@ -641,59 +718,74 @@ pub const Exe = struct {
         };
     }
 
-    /// Exe keeps a reference to script for its lifetime or until this function
+    /// LibOrExeStep keeps a reference to script for its lifetime or until this function
     /// is called again.
-    pub fn setLinkerScriptContents(self: &Exe, script: []const u8) {
+    pub fn setLinkerScriptContents(self: &LibOrExeStep, script: []const u8) {
         self.linker_script = LinkerScript.Embed { script };
     }
 
-    pub fn setLinkerScriptPath(self: &Exe, path: []const u8) {
+    pub fn setLinkerScriptPath(self: &LibOrExeStep, path: []const u8) {
         self.linker_script = LinkerScript.Path { path };
     }
 
-    pub fn linkLibrary(self: &Exe, name: []const u8) {
+    pub fn linkSystemLibrary(self: &LibOrExeStep, name: []const u8) {
         %%self.link_libs.put(name);
     }
 
-    pub fn setVerbose(self: &Exe, value: bool) {
+    pub fn setVerbose(self: &LibOrExeStep, value: bool) {
         self.verbose = value;
     }
 
-    pub fn setRelease(self: &Exe, value: bool) {
+    pub fn setRelease(self: &LibOrExeStep, value: bool) {
         self.release = value;
     }
 
-    pub fn setOutputPath(self: &Exe, value: []const u8) {
+    pub fn setOutputPath(self: &LibOrExeStep, value: []const u8) {
         self.output_path = value;
     }
 
     fn make(step: &Step) -> %void {
-        const exe = @fieldParentPtr(Exe, "step", step);
-        const builder = exe.builder;
+        const self = @fieldParentPtr(LibOrExeStep, "step", step);
+        const builder = self.builder;
 
         var zig_args = List([]const u8).init(builder.allocator);
         defer zig_args.deinit();
 
-        %%zig_args.append("build_exe");
-        %%zig_args.append(builder.pathFromRoot(exe.root_src));
+        const cmd = switch (self.kind) {
+            Kind.Lib => "build_lib",
+            Kind.Exe => "build_exe",
+        };
+        %%zig_args.append(cmd);
+        %%zig_args.append(builder.pathFromRoot(self.root_src));
 
-        if (exe.verbose) {
+        if (self.verbose) {
             %%zig_args.append("--verbose");
         }
 
-        if (exe.release) {
+        if (self.release) {
             %%zig_args.append("--release");
         }
 
-        if (const output_path ?= exe.output_path) {
+        if (const output_path ?= self.output_path) {
             %%zig_args.append("--output");
             %%zig_args.append(builder.pathFromRoot(output_path));
         }
 
         %%zig_args.append("--name");
-        %%zig_args.append(exe.name);
+        %%zig_args.append(self.name);
 
-        switch (exe.target) {
+        if (self.kind == Kind.Lib and !self.static) {
+            %%zig_args.append("--ver-major");
+            %%zig_args.append(builder.fmt("{}", self.version.major));
+
+            %%zig_args.append("--ver-minor");
+            %%zig_args.append(builder.fmt("{}", self.version.minor));
+
+            %%zig_args.append("--ver-patch");
+            %%zig_args.append(builder.fmt("{}", self.version.patch));
+        }
+
+        switch (self.target) {
             Target.Native => {},
             Target.Cross => |cross_target| {
                 %%zig_args.append("--target-arch");
@@ -707,7 +799,7 @@ pub const Exe = struct {
             },
         }
 
-        switch (exe.linker_script) {
+        switch (self.linker_script) {
             LinkerScript.None => {},
             LinkerScript.Embed => |script| {
                 const tmp_file_name = "linker.ld.tmp"; // TODO issue #298
@@ -723,7 +815,7 @@ pub const Exe = struct {
         }
 
         {
-            var it = exe.link_libs.iterator();
+            var it = self.link_libs.iterator();
             while (true) {
                 const entry = it.next() ?? break;
                 %%zig_args.append("--library");
@@ -746,7 +838,118 @@ pub const Exe = struct {
             %%zig_args.append(lib_path);
         }
 
-        builder.spawnChild(builder.zig_exe, zig_args.toSliceConst());
+        %%builder.spawnChild(builder.zig_exe, zig_args.toSliceConst());
+
+        if (self.kind == Kind.Lib and !self.static) {
+            // sym link for libfoo.so.1 to libfoo.so.1.2.3
+            %%os.atomicSymLink(builder.allocator, self.out_filename, self.out_filename_major_only);
+            // sym link for libfoo.so to libfoo.so.1
+            %%os.atomicSymLink(builder.allocator, self.out_filename_major_only, self.out_filename_name_only);
+        }
+    }
+};
+
+pub const ObjectStep = struct {
+    step: Step,
+    builder: &Builder,
+    root_src: []const u8,
+    name: []const u8,
+    target: Target,
+    verbose: bool,
+    release: bool,
+    output_path: ?[]const u8,
+
+    pub fn init(builder: &Builder, name: []const u8, root_src: []const u8) -> ObjectStep {
+        ObjectStep {
+            .builder = builder,
+            .verbose = false,
+            .release = false,
+            .root_src = root_src,
+            .name = name,
+            .target = Target.Native,
+            .step = Step.init(name, builder.allocator, make),
+            .output_path = null,
+        }
+    }
+
+    pub fn setTarget(self: &ObjectStep, target_arch: Arch, target_os: Os, target_environ: Environ) {
+        self.target = Target.Cross {
+            CrossTarget {
+                .arch = target_arch,
+                .os = target_os,
+                .environ = target_environ,
+            }
+        };
+    }
+
+    pub fn setVerbose(self: &ObjectStep, value: bool) {
+        self.verbose = value;
+    }
+
+    pub fn setRelease(self: &ObjectStep, value: bool) {
+        self.release = value;
+    }
+
+    pub fn setOutputPath(self: &ObjectStep, value: []const u8) {
+        self.output_path = value;
+    }
+
+    fn make(step: &Step) -> %void {
+        const self = @fieldParentPtr(ObjectStep, "step", step);
+        const builder = self.builder;
+
+        var zig_args = List([]const u8).init(builder.allocator);
+        defer zig_args.deinit();
+
+        %%zig_args.append("build_obj");
+        %%zig_args.append(builder.pathFromRoot(self.root_src));
+
+        if (self.verbose) {
+            %%zig_args.append("--verbose");
+        }
+
+        if (self.release) {
+            %%zig_args.append("--release");
+        }
+
+        if (const output_path ?= self.output_path) {
+            %%zig_args.append("--output");
+            %%zig_args.append(builder.pathFromRoot(output_path));
+        }
+
+        %%zig_args.append("--name");
+        %%zig_args.append(self.name);
+
+        switch (self.target) {
+            Target.Native => {},
+            Target.Cross => |cross_target| {
+                %%zig_args.append("--target-arch");
+                %%zig_args.append(@enumTagName(cross_target.arch));
+
+                %%zig_args.append("--target-os");
+                %%zig_args.append(@enumTagName(cross_target.os));
+
+                %%zig_args.append("--target-environ");
+                %%zig_args.append(@enumTagName(cross_target.environ));
+            },
+        }
+
+        for (builder.include_paths.toSliceConst()) |include_path| {
+            %%zig_args.append("-isystem");
+            %%zig_args.append(include_path);
+        }
+
+        for (builder.rpaths.toSliceConst()) |rpath| {
+            %%zig_args.append("-rpath");
+            %%zig_args.append(rpath);
+        }
+
+        for (builder.lib_paths.toSliceConst()) |lib_path| {
+            %%zig_args.append("--library-path");
+            %%zig_args.append(lib_path);
+        }
+
+        %%builder.spawnChild(builder.zig_exe, zig_args.toSliceConst());
     }
 };
 
@@ -836,7 +1039,7 @@ pub const AsmStep = struct {
             },
         }
 
-        builder.spawnChild(builder.zig_exe, zig_args.toSliceConst());
+        %%builder.spawnChild(builder.zig_exe, zig_args.toSliceConst());
     }
 };
 
@@ -941,7 +1144,7 @@ pub const LinkStep = struct {
         self.linker_script = LinkerScript.Path { path };
     }
 
-    pub fn linkLibrary(self: &LinkStep, name: []const u8) {
+    pub fn linkSystemLibrary(self: &LinkStep, name: []const u8) {
         %%self.link_libs.put(name);
     }
 
@@ -1047,7 +1250,7 @@ pub const LinkStep = struct {
             %%zig_args.append(lib_path);
         }
 
-        builder.spawnChild(builder.zig_exe, zig_args.toSliceConst());
+        %%builder.spawnChild(builder.zig_exe, zig_args.toSliceConst());
     }
 };
 
@@ -1083,7 +1286,7 @@ pub const TestStep = struct {
         self.release = value;
     }
 
-    pub fn linkLibrary(self: &TestStep, name: []const u8) {
+    pub fn linkSystemLibrary(self: &TestStep, name: []const u8) {
         %%self.link_libs.put(name);
     }
 
@@ -1147,7 +1350,7 @@ pub const TestStep = struct {
             %%zig_args.append(lib_path);
         }
 
-        builder.spawnChild(builder.zig_exe, zig_args.toSliceConst());
+        %%builder.spawnChild(builder.zig_exe, zig_args.toSliceConst());
     }
 };
 
@@ -1207,7 +1410,7 @@ pub const CLibrary = struct {
         }
     }
 
-    pub fn linkLibrary(self: &CLibrary, name: []const u8) {
+    pub fn linkSystemLibrary(self: &CLibrary, name: []const u8) {
         %%self.link_libs.put(name);
     }
 
@@ -1276,7 +1479,7 @@ pub const CLibrary = struct {
                 %%cc_args.append(dir);
             }
 
-            builder.spawnChild(cc, cc_args.toSliceConst());
+            %return builder.spawnChild(cc, cc_args.toSliceConst());
 
             %%self.object_files.append(o_file);
         }
@@ -1300,7 +1503,7 @@ pub const CLibrary = struct {
                 %%cc_args.append(builder.pathFromRoot(object_file));
             }
 
-            builder.spawnChild(cc, cc_args.toSliceConst());
+            %return builder.spawnChild(cc, cc_args.toSliceConst());
 
             // sym link for libfoo.so.1 to libfoo.so.1.2.3
             %%os.atomicSymLink(builder.allocator, self.out_filename, self.major_only_filename);
@@ -1347,7 +1550,7 @@ pub const CExecutable = struct {
         }
     }
 
-    pub fn linkLibrary(self: &CExecutable, name: []const u8) {
+    pub fn linkSystemLibrary(self: &CExecutable, name: []const u8) {
         %%self.link_libs.put(name);
     }
 
@@ -1356,6 +1559,14 @@ pub const CExecutable = struct {
         %%self.full_path_libs.append(clib.out_filename);
     }
 
+    pub fn linkLibrary(self: &CExecutable, lib: &LibOrExeStep) {
+        assert(lib.kind == LibOrExeStep.Kind.Lib);
+        self.step.dependOn(&lib.step);
+        %%self.full_path_libs.append(lib.out_filename);
+        // TODO should be some kind of isolated directory that only has this header in it
+        %%self.include_dirs.append(self.builder.out_dir);
+    }
+
     pub fn addSourceFile(self: &CExecutable, file: []const u8) {
         %%self.source_files.append(file);
     }
@@ -1395,7 +1606,7 @@ pub const CExecutable = struct {
             %%cc_args.resize(0);
 
             %%cc_args.append("-c");
-            %%cc_args.append(source_file);
+            %%cc_args.append(builder.pathFromRoot(source_file));
 
             // TODO don't dump the .o file in the same place as the source file
             const o_file = builder.fmt("{}{}", source_file, self.target.oFileExt());
@@ -1409,10 +1620,10 @@ pub const CExecutable = struct {
 
             for (self.include_dirs.toSliceConst()) |dir| {
                 %%cc_args.append("-I");
-                %%cc_args.append(dir);
+                %%cc_args.append(builder.pathFromRoot(dir));
             }
 
-            builder.spawnChild(cc, cc_args.toSliceConst());
+            %return builder.spawnChild(cc, cc_args.toSliceConst());
 
             %%self.object_files.append(o_file);
         }
@@ -1436,7 +1647,7 @@ pub const CExecutable = struct {
             %%cc_args.append(full_path_lib);
         }
 
-        builder.spawnChild(cc, cc_args.toSliceConst());
+        %return builder.spawnChild(cc, cc_args.toSliceConst());
     }
 
     pub fn setTarget(self: &CExecutable, target_arch: Arch, target_os: Os, target_environ: Environ) {
@@ -1475,7 +1686,7 @@ pub const CommandStep = struct {
         const self = @fieldParentPtr(CommandStep, "step", step);
 
         // TODO set cwd
-        self.builder.spawnChildEnvMap(self.env_map, self.exe_path, self.args);
+        return self.builder.spawnChildEnvMap(self.env_map, self.exe_path, self.args);
     }
 };
 
@@ -1552,7 +1763,7 @@ pub const WriteFileStep = struct {
     fn make(step: &Step) -> %void {
         const self = @fieldParentPtr(WriteFileStep, "step", step);
         const full_path = self.builder.pathFromRoot(self.file_path);
-        const full_path_dir = %%os.path.dirname(self.builder.allocator, full_path);
+        const full_path_dir = os.path.dirname(full_path);
         os.makePath(self.builder.allocator, full_path_dir) %% |err| {
             %%io.stderr.printf("unable to make path {}: {}\n", full_path_dir, @errorName(err));
             return err;
diff --git a/std/cstr.zig b/std/cstr.zig
index 21cf393d46..0934b9967f 100644
--- a/std/cstr.zig
+++ b/std/cstr.zig
@@ -1,11 +1,6 @@
-const List = @import("list.zig").List;
-const mem = @import("mem.zig");
-const Allocator = mem.Allocator;
 const debug = @import("debug.zig");
 const assert = debug.assert;
 
-const strlen = len;
-
 pub fn len(ptr: &const u8) -> usize {
     var count: usize = 0;
     while (ptr[count] != 0; count += 1) {}
@@ -25,139 +20,11 @@ pub fn cmp(a: &const u8, b: &const u8) -> i8 {
 }
 
 pub fn toSliceConst(str: &const u8) -> []const u8 {
-    return str[0...strlen(str)];
+    return str[0...len(str)];
 }
 
 pub fn toSlice(str: &u8) -> []u8 {
-    return str[0...strlen(str)];
-}
-
-
-/// A buffer that allocates memory and maintains a null byte at the end.
-pub const Buffer0 = struct {
-    list: List(u8),
-
-    /// Must deinitialize with deinit.
-    pub fn initEmpty(allocator: &Allocator) -> %Buffer0 {
-        return initSize(allocator, 0);
-    }
-
-    /// Must deinitialize with deinit.
-    pub fn initFromMem(allocator: &Allocator, m: []const u8) -> %Buffer0 {
-        var self = %return initSize(allocator, m.len);
-        mem.copy(u8, self.list.items, m);
-        return self;
-    }
-
-    /// Must deinitialize with deinit.
-    pub fn initFromCStr(allocator: &Allocator, s: &const u8) -> %Buffer0 {
-        return Buffer0.initFromMem(allocator, s[0...strlen(s)]);
-    }
-
-    /// Must deinitialize with deinit.
-    pub fn initFromOther(cbuf: &const Buffer0) -> %Buffer0 {
-        return Buffer0.initFromMem(cbuf.list.allocator, cbuf.list.items[0...cbuf.len()]);
-    }
-
-    /// Must deinitialize with deinit.
-    pub fn initFromSlice(other: &const Buffer0, start: usize, end: usize) -> %Buffer0 {
-        return Buffer0.initFromMem(other.list.allocator, other.list.items[start...end]);
-    }
-
-    /// Must deinitialize with deinit.
-    pub fn initSize(allocator: &Allocator, size: usize) -> %Buffer0 {
-        var self = Buffer0 {
-            .list = List(u8).init(allocator),
-        };
-        %return self.resize(size);
-        return self;
-    }
-
-    pub fn deinit(self: &Buffer0) {
-        self.list.deinit();
-    }
-
-    pub fn toSlice(self: &Buffer0) -> []u8 {
-        return self.list.toSlice()[0...self.len()];
-    }
-
-    pub fn toSliceConst(self: &const Buffer0) -> []const u8 {
-        return self.list.toSliceConst()[0...self.len()];
-    }
-
-    pub fn resize(self: &Buffer0, new_len: usize) -> %void {
-        %return self.list.resize(new_len + 1);
-        self.list.items[self.len()] = 0;
-    }
-
-    pub fn len(self: &const Buffer0) -> usize {
-        return self.list.len - 1;
-    }
-
-    pub fn appendMem(self: &Buffer0, m: []const u8) -> %void {
-        const old_len = self.len();
-        %return self.resize(old_len + m.len);
-        mem.copy(u8, self.list.toSlice()[old_len...], m);
-    }
-
-    pub fn appendOther(self: &Buffer0, other: &const Buffer0) -> %void {
-        return self.appendMem(other.toSliceConst());
-    }
-
-    pub fn appendCStr(self: &Buffer0, s: &const u8) -> %void {
-        self.appendMem(s[0...strlen(s)])
-    }
-
-    pub fn appendByte(self: &Buffer0, byte: u8) -> %void {
-        %return self.resize(self.len() + 1);
-        self.list.items[self.len() - 1] = byte;
-    }
-
-    pub fn eqlMem(self: &const Buffer0, m: []const u8) -> bool {
-        if (self.len() != m.len) return false;
-        return mem.cmp(u8, self.list.items[0...m.len], m) == mem.Cmp.Equal;
-    }
-
-    pub fn eqlCStr(self: &const Buffer0, s: &const u8) -> bool {
-        self.eqlMem(s[0...strlen(s)])
-    }
-
-    pub fn eqlOther(self: &const Buffer0, other: &const Buffer0) -> bool {
-        self.eqlMem(other.list.items[0...other.len()])
-    }
-
-    pub fn startsWithMem(self: &const Buffer0, m: []const u8) -> bool {
-        if (self.len() < m.len) return false;
-        return mem.cmp(u8, self.list.items[0...m.len], m) == mem.Cmp.Equal;
-    }
-
-    pub fn startsWithOther(self: &const Buffer0, other: &const Buffer0) -> bool {
-        self.startsWithMem(other.list.items[0...other.len()])
-    }
-
-    pub fn startsWithCStr(self: &const Buffer0, s: &const u8) -> bool {
-        self.startsWithMem(s[0...strlen(s)])
-    }
-};
-
-test "simple Buffer0" {
-    var buf = %%Buffer0.initEmpty(&debug.global_allocator);
-    assert(buf.len() == 0);
-    %%buf.appendCStr(c"hello");
-    %%buf.appendByte(' ');
-    %%buf.appendMem("world");
-    assert(buf.eqlCStr(c"hello world"));
-    assert(buf.eqlMem("hello world"));
-    assert(mem.eql(u8, buf.toSliceConst(), "hello world"));
-
-    var buf2 = %%Buffer0.initFromOther(&buf);
-    assert(buf.eqlOther(&buf2));
-
-    assert(buf.startsWithMem("hell"));
-    assert(buf.startsWithCStr(c"hell"));
-
-    %%buf2.resize(4);
-    assert(buf.startsWithOther(&buf2));
+    return str[0...len(str)];
 }
 
 test "cstr fns" {
diff --git a/std/index.zig b/std/index.zig
index 26518d6de9..5deb3d37c4 100644
--- a/std/index.zig
+++ b/std/index.zig
@@ -1,4 +1,5 @@
 pub const base64 = @import("base64.zig");
+pub const buffer = @import("buffer.zig");
 pub const build = @import("build.zig");
 pub const c = @import("c/index.zig");
 pub const cstr = @import("cstr.zig");
diff --git a/std/io.zig b/std/io.zig
index e9c70d9611..2b48e1d899 100644
--- a/std/io.zig
+++ b/std/io.zig
@@ -10,7 +10,7 @@ const debug = @import("debug.zig");
 const assert = debug.assert;
 const os = @import("os/index.zig");
 const mem = @import("mem.zig");
-const Buffer0 = @import("cstr.zig").Buffer0;
+const Buffer = @import("buffer.zig").Buffer;
 const fmt = @import("fmt.zig");
 
 pub var stdin = InStream {
@@ -326,7 +326,7 @@ pub const InStream = struct {
         return usize(stat.size);
     }
 
-    pub fn readAll(is: &InStream, buf: &Buffer0) -> %void {
+    pub fn readAll(is: &InStream, buf: &Buffer) -> %void {
         %return buf.resize(os.page_size);
 
         var actual_buf_len: usize = 0;
diff --git a/std/list.zig b/std/list.zig
index b20cd06fef..3052fb3243 100644
--- a/std/list.zig
+++ b/std/list.zig
@@ -44,6 +44,11 @@ pub fn List(comptime T: type) -> type{
             l.len = new_len;
         }
 
+        pub fn resizeDown(l: &Self, new_len: usize) {
+            assert(new_len <= l.len);
+            l.len = new_len;
+        }
+
         pub fn ensureCapacity(l: &Self, new_capacity: usize) -> %void {
             var better_capacity = l.items.len;
             if (better_capacity >= new_capacity) return;
diff --git a/std/os/index.zig b/std/os/index.zig
index 0113706796..52e26d9e2b 100644
--- a/std/os/index.zig
+++ b/std/os/index.zig
@@ -226,11 +226,11 @@ pub fn posixDup2(old_fd: i32, new_fd: i32) -> %void {
 pub fn posixExecve(exe_path: []const u8, argv: []const []const u8, env_map: &const BufMap,
     allocator: &Allocator) -> %void
 {
-    const argv_buf = %return allocator.alloc(?&const u8, argv.len + 2);
-    mem.set(?&const u8, argv_buf, null);
+    const argv_buf = %return allocator.alloc(?&u8, argv.len + 2);
+    mem.set(?&u8, argv_buf, null);
     defer {
         for (argv_buf) |arg| {
-            const arg_buf = if (const ptr ?= arg) ptr[0...cstr.len(ptr)] else break;
+            const arg_buf = if (const ptr ?= arg) cstr.toSlice(ptr) else break;
             allocator.free(arg_buf);
         }
         allocator.free(argv_buf);
@@ -253,11 +253,11 @@ pub fn posixExecve(exe_path: []const u8, argv: []const []const u8, env_map: &con
     argv_buf[argv.len + 1] = null;
 
     const envp_count = env_map.count();
-    const envp_buf = %return allocator.alloc(?&const u8, envp_count + 1);
-    mem.set(?&const u8, envp_buf, null);
+    const envp_buf = %return allocator.alloc(?&u8, envp_count + 1);
+    mem.set(?&u8, envp_buf, null);
     defer {
         for (envp_buf) |env| {
-            const env_buf = if (const ptr ?= env) ptr[0...cstr.len(ptr)] else break;
+            const env_buf = if (const ptr ?= env) cstr.toSlice(ptr) else break;
             allocator.free(env_buf);
         }
         allocator.free(envp_buf);
@@ -380,7 +380,7 @@ pub const args = struct {
     }
     pub fn at(i: usize) -> []const u8 {
         const s = raw[i];
-        return s[0...cstr.len(s)];
+        return cstr.toSlice(s);
     }
 };
 
@@ -397,7 +397,7 @@ pub fn getCwd(allocator: &Allocator) -> %[]u8 {
             return error.Unexpected;
         }
 
-        return buf;
+        return cstr.toSlice(buf.ptr);
     }
 }
 
@@ -572,22 +572,39 @@ pub fn makeDir(allocator: &Allocator, dir_path: []const u8) -> %void {
 /// Calls makeDir recursively to make an entire path. Returns success if the path
 /// already exists and is a directory.
 pub fn makePath(allocator: &Allocator, full_path: []const u8) -> %void {
-    const child_dir = %return path.dirname(allocator, full_path);
-    defer allocator.free(child_dir);
+    const resolved_path = %return path.resolve(allocator, full_path);
+    defer allocator.free(resolved_path);
 
-    if (mem.eql(u8, child_dir, full_path))
-        return;
-
-    makePath(allocator, child_dir) %% |err| {
-        if (err != error.PathAlreadyExists)
-            return err;
-    };
-
-    makeDir(allocator, full_path) %% |err| {
-        if (err != error.PathAlreadyExists)
-            return err;
-        // TODO stat the file and return an error if it's not a directory
-    };
+    var end_index: usize = resolved_path.len;
+    while (true) {
+        makeDir(allocator, resolved_path[0...end_index]) %% |err| {
+            if (err == error.PathAlreadyExists) {
+                // TODO stat the file and return an error if it's not a directory
+                // this is important because otherwise a dangling symlink
+                // could cause an infinite loop
+                if (end_index == resolved_path.len)
+                    return;
+            } else if (err == error.FileNotFound) {
+                // march end_index backward until next path component
+                while (true) {
+                    end_index -= 1;
+                    if (resolved_path[end_index] == '/')
+                        break;
+                }
+                continue;
+            } else {
+                return err;
+            }
+        };
+        if (end_index == resolved_path.len)
+            return;
+        // march end_index forward until next path component
+        while (true) {
+            end_index += 1;
+            if (end_index == resolved_path.len or resolved_path[end_index] == '/')
+                break;
+        }
+    }
 }
 
 /// Returns ::error.DirNotEmpty if the directory is not empty.
@@ -739,7 +756,7 @@ pub const Dir = struct {
         const next_index = self.index + linux_entry.d_reclen;
         self.index = next_index;
 
-        const name = (&linux_entry.d_name)[0...cstr.len(&linux_entry.d_name)];
+        const name = cstr.toSlice(&linux_entry.d_name);
 
         // skip . and .. entries
         if (mem.eql(u8, name, ".") or mem.eql(u8, name, "..")) {
diff --git a/std/os/path.zig b/std/os/path.zig
index 66c07ad6de..1f82153a89 100644
--- a/std/os/path.zig
+++ b/std/os/path.zig
@@ -2,7 +2,11 @@ const debug = @import("../debug.zig");
 const assert = debug.assert;
 const mem = @import("../mem.zig");
 const Allocator = mem.Allocator;
+const os = @import("index.zig");
 
+pub const sep = '/';
+
+/// Naively combines a series of paths with the native path seperator.
 /// Allocates memory for the result, which must be freed by the caller.
 pub fn join(allocator: &Allocator, paths: ...) -> %[]u8 {
     assert(paths.len >= 2);
@@ -26,8 +30,8 @@ pub fn join(allocator: &Allocator, paths: ...) -> %[]u8 {
         mem.copy(u8, buf[buf_index...], arg);
         buf_index += arg.len;
         if (path_i >= paths.len) break;
-        if (arg[arg.len - 1] != '/') {
-            buf[buf_index] = '/';
+        if (arg[arg.len - 1] != sep) {
+            buf[buf_index] = sep;
             buf_index += 1;
         }
     }
@@ -43,22 +47,128 @@ test "os.path.join" {
     assert(mem.eql(u8, %%join(&debug.global_allocator, "/a/", "b/", "c"), "/a/b/c"));
 }
 
-pub fn dirname(allocator: &Allocator, path: []const u8) -> %[]u8 {
-    if (path.len != 0) {
-        var last_index: usize = path.len - 1;
-        if (path[last_index] == '/')
-            last_index -= 1;
+pub fn isAbsolute(path: []const u8) -> bool {
+    switch (@compileVar("os")) {
+        Os.windows => @compileError("Unsupported OS"),
+        else => return path[0] == sep,
+    }
+}
 
-        var i: usize = last_index;
+/// This function is like a series of `cd` statements executed one after another.
+/// The result does not have a trailing path separator.
+pub fn resolve(allocator: &Allocator, args: ...) -> %[]u8 {
+    var paths: [args.len][]const u8 = undefined;
+    comptime var arg_i = 0;
+    inline while (arg_i < args.len; arg_i += 1) {
+        paths[arg_i] = args[arg_i];
+    }
+    return resolveSlice(allocator, paths);
+}
+
+pub fn resolveSlice(allocator: &Allocator, paths: []const []const u8) -> %[]u8 {
+    if (paths.len == 0)
+        return os.getCwd(allocator);
+
+    var first_index: usize = 0;
+    var have_abs = false;
+    var max_size: usize = 0;
+    for (paths) |p, i| {
+        if (isAbsolute(p)) {
+            first_index = i;
+            have_abs = true;
+            max_size = 0;
+        }
+        max_size += p.len + 1;
+    }
+
+    var result: []u8 = undefined;
+    var result_index: usize = 0;
+
+    if (have_abs) {
+        result = %return allocator.alloc(u8, max_size);
+    } else {
+        const cwd = %return os.getCwd(allocator);
+        defer allocator.free(cwd);
+        result = %return allocator.alloc(u8, max_size + cwd.len + 1);
+        mem.copy(u8, result, cwd);
+        result_index += cwd.len;
+    }
+    %defer allocator.free(result);
+
+    for (paths[first_index...]) |p, i| {
+        var it = mem.split(p, '/');
         while (true) {
-            const c = path[i];
-            if (c == '/')
-                return mem.dupe(allocator, u8, path[0...i]);
-            if (i == 0)
-                break;
-            i -= 1;
+            const component = it.next() ?? break;
+            if (mem.eql(u8, component, ".")) {
+                continue;
+            } else if (mem.eql(u8, component, "..")) {
+                while (true) {
+                    if (result_index == 0)
+                        break;
+                    result_index -= 1;
+                    if (result[result_index] == '/')
+                        break;
+                }
+            } else {
+                result[result_index] = '/';
+                result_index += 1;
+                mem.copy(u8, result[result_index...], component);
+                result_index += component.len;
+            }
         }
     }
 
-    return mem.dupe(allocator, u8, ".");
+    if (result_index == 0) {
+        result[0] = '/';
+        result_index += 1;
+    }
+
+    return result[0...result_index];
+}
+
+test "os.path.resolve" {
+    assert(mem.eql(u8, testResolve("/a/b", "c"), "/a/b/c"));
+    assert(mem.eql(u8, testResolve("/a/b", "c", "//d", "e///"), "/d/e"));
+    assert(mem.eql(u8, testResolve("/a/b/c", "..", "../"), "/a"));
+    assert(mem.eql(u8, testResolve("/", "..", ".."), "/"));
+}
+fn testResolve(args: ...) -> []u8 {
+    return %%resolve(&debug.global_allocator, args);
+}
+
+pub fn dirname(path: []const u8) -> []const u8 {
+    if (path.len == 0)
+        return path[0...0];
+    var end_index: usize = path.len - 1;
+    while (path[end_index] == '/') {
+        if (end_index == 0)
+            return path[0...1];
+        end_index -= 1;
+    }
+
+    while (path[end_index] != '/') {
+        if (end_index == 0)
+            return path[0...0];
+        end_index -= 1;
+    }
+
+    if (end_index == 0 and path[end_index] == '/')
+        return path[0...1];
+
+    return path[0...end_index];
+}
+
+test "os.path.dirname" {
+    testDirname("/a/b/c", "/a/b");
+    testDirname("/a/b/c///", "/a/b");
+    testDirname("/a", "/");
+    testDirname("/", "/");
+    testDirname("////", "/");
+    testDirname("", "");
+    testDirname("a", "");
+    testDirname("a/", "");
+    testDirname("a//", "");
+}
+fn testDirname(input: []const u8, expected_output: []const u8) {
+    assert(mem.eql(u8, dirname(input), expected_output));
 }
diff --git a/test/build_examples.zig b/test/build_examples.zig
index 72bed9d296..dc2e793da4 100644
--- a/test/build_examples.zig
+++ b/test/build_examples.zig
@@ -5,4 +5,5 @@ pub fn addCases(cases: &tests.BuildExamplesContext) {
     cases.addC("example/hello_world/hello_libc.zig");
     cases.add("example/cat/main.zig");
     cases.add("example/guess_number/main.zig");
+    cases.addBuildFile("example/shared_library/build.zig");
 }
diff --git a/test/tests.zig b/test/tests.zig
index d760856339..3340e5913c 100644
--- a/test/tests.zig
+++ b/test/tests.zig
@@ -4,7 +4,7 @@ const build = std.build;
 const os = std.os;
 const StdIo = os.ChildProcess.StdIo;
 const Term = os.ChildProcess.Term;
-const Buffer0 = std.cstr.Buffer0;
+const Buffer = std.buffer.Buffer;
 const io = std.io;
 const mem = std.mem;
 const fmt = std.fmt;
@@ -116,7 +116,7 @@ pub fn addPkgTests(b: &build.Builder, test_filter: ?[]const u8, root_src: []cons
             these_tests.setFilter(test_filter);
             these_tests.setRelease(release);
             if (link_libc) {
-                these_tests.linkLibrary("c");
+                these_tests.linkSystemLibrary("c");
             }
             step.dependOn(&these_tests.step);
         }
@@ -211,8 +211,8 @@ pub const CompareOutputContext = struct {
                 },
             };
 
-            var stdout = %%Buffer0.initEmpty(b.allocator);
-            var stderr = %%Buffer0.initEmpty(b.allocator);
+            var stdout = Buffer.initNull(b.allocator);
+            var stderr = Buffer.initNull(b.allocator);
 
             %%(??child.stdout).readAll(&stdout);
             %%(??child.stderr).readAll(&stderr);
@@ -388,7 +388,7 @@ pub const CompareOutputContext = struct {
                     exe.setOutputPath(exe_path);
                     exe.setRelease(release);
                     if (case.link_libc) {
-                        exe.linkLibrary("c");
+                        exe.linkSystemLibrary("c");
                     }
 
                     for (case.sources.toSliceConst()) |src_file| {
@@ -415,7 +415,7 @@ pub const CompareOutputContext = struct {
                 const exe = b.addExecutable("test", root_src);
                 exe.setOutputPath(exe_path);
                 if (case.link_libc) {
-                    exe.linkLibrary("c");
+                    exe.linkSystemLibrary("c");
                 }
 
                 for (case.sources.toSliceConst()) |src_file| {
@@ -537,8 +537,8 @@ pub const CompileErrorContext = struct {
                 },
             };
 
-            var stdout_buf = %%Buffer0.initEmpty(b.allocator);
-            var stderr_buf = %%Buffer0.initEmpty(b.allocator);
+            var stdout_buf = Buffer.initNull(b.allocator);
+            var stderr_buf = Buffer.initNull(b.allocator);
 
             %%(??child.stdout).readAll(&stdout_buf);
             %%(??child.stderr).readAll(&stderr_buf);
@@ -657,6 +657,35 @@ pub const BuildExamplesContext = struct {
         self.addAllArgs(root_src, false);
     }
 
+    pub fn addBuildFile(self: &BuildExamplesContext, build_file: []const u8) {
+        const b = self.b;
+
+        const annotated_case_name = b.fmt("build {}", build_file);
+        if (const filter ?= self.test_filter) {
+            if (mem.indexOf(u8, annotated_case_name, filter) == null)
+                return;
+        }
+
+        var zig_args = List([]const u8).init(b.allocator);
+        %%zig_args.append("build");
+
+        %%zig_args.append("--build-file");
+        %%zig_args.append(b.pathFromRoot(build_file));
+
+        %%zig_args.append("test");
+
+        if (b.verbose) {
+            %%zig_args.append("--verbose");
+        }
+
+        const run_cmd = b.addCommand(b.out_dir, b.env_map, b.zig_exe, zig_args.toSliceConst());
+
+        const log_step = b.addLog("PASS {}\n", annotated_case_name);
+        log_step.step.dependOn(&run_cmd.step);
+
+        self.step.dependOn(&log_step.step);
+    }
+
     pub fn addAllArgs(self: &BuildExamplesContext, root_src: []const u8, link_libc: bool) {
         const b = self.b;
 
@@ -671,7 +700,7 @@ pub const BuildExamplesContext = struct {
             const exe = b.addExecutable("test", root_src);
             exe.setRelease(release);
             if (link_libc) {
-                exe.linkLibrary("c");
+                exe.linkSystemLibrary("c");
             }
 
             const log_step = b.addLog("PASS {}\n", annotated_case_name);
@@ -774,8 +803,8 @@ pub const ParseHContext = struct {
                 },
             };
 
-            var stdout_buf = %%Buffer0.initEmpty(b.allocator);
-            var stderr_buf = %%Buffer0.initEmpty(b.allocator);
+            var stdout_buf = Buffer.initNull(b.allocator);
+            var stderr_buf = Buffer.initNull(b.allocator);
 
             %%(??child.stdout).readAll(&stdout_buf);
             %%(??child.stderr).readAll(&stderr_buf);