diff --git a/bootstrap/Compilation.zig b/bootstrap/Compilation.zig
index 3f9a3f8..798b6a6 100644
--- a/bootstrap/Compilation.zig
+++ b/bootstrap/Compilation.zig
@@ -87,6 +87,7 @@ pub fn compileBuildExecutable(context: *const Context, arguments: [][*:0]u8) !vo
             .generate_debug_information = true,
             .name = "build",
             .is_test = false,
+            .c_source_files = &.{},
         },
     };
 
@@ -102,13 +103,18 @@ pub fn compileBuildExecutable(context: *const Context, arguments: [][*:0]u8) !vo
         else => false,
     };
     if (!success) {
-        // std.debug.print("The following command terminated with failure ({s}): {s}\n", .{ @tagName(result.term), argv });
-        // if (result.stdout.len > 0) {
-        //     std.debug.print("STDOUT:\n{s}\n", .{result.stdout});
-        // }
-        // if (result.stderr.len > 0) {
-        //     std.debug.print("STDOUT:\n{s}\n", .{result.stderr});
-        // }
+        try write(.panic, "The following command terminated with failure: (");
+        try write(.panic, @tagName(result.term));
+        try write(.panic, "):\n");
+        for (argv) |arg| {
+            try write(.panic, arg);
+            try write(.panic, ", ");
+        }
+        try write(.panic, "\n");
+        try write(.panic, result.stdout);
+        try write(.panic, "\n");
+        try write(.panic, result.stderr);
+        try write(.panic, "\n");
         std.os.abort();
     }
 }
@@ -2181,6 +2187,7 @@ pub fn buildExecutable(context: *const Context, arguments: [][*:0]u8, options: E
     var maybe_only_parse: ?bool = null;
     var link_libc = false;
     var maybe_executable_name: ?[]const u8 = null;
+    var c_source_files = UnpinnedArray([*:0]u8){};
     const generate_debug_information = true;
 
     if (arguments.len == 0) return error.InvalidInput;
@@ -2287,6 +2294,17 @@ pub fn buildExecutable(context: *const Context, arguments: [][*:0]u8, options: E
             } else {
                 reportUnterminatedArgumentError(current_argument);
             }
+        } else if (byte_equal(current_argument, "-c_source_files")) {
+            if (i + 1 != arguments.len) {
+                i += 1;
+
+                try c_source_files.ensure_capacity(context.my_allocator, @intCast(arguments.len - i));
+                while (i < arguments.len) : (i += 1) {
+                    c_source_files.append_with_capacity(arguments[i]);
+                }
+            } else {
+                reportUnterminatedArgumentError(current_argument);
+            }
         } else {
             @panic(current_argument);
             // std.debug.panic("Unrecognized argument: {s}", .{current_argument});
@@ -2328,6 +2346,7 @@ pub fn buildExecutable(context: *const Context, arguments: [][*:0]u8, options: E
             .generate_debug_information = generate_debug_information,
             .name = executable_name,
             .is_test = options.is_test,
+            .c_source_files = c_source_files.slice(),
         },
     };
 
@@ -9886,7 +9905,7 @@ pub const Builder = struct {
                 break :blk switch (result.value) {
                     .@"comptime" => |ct| switch (ct) {
                         .global => |global| switch (global.initial_value) {
-                            .function_definition => .{
+                            .function_definition, .function_declaration => .{
                                 .value = .{
                                     .@"comptime" = .{
                                         .global = global,
@@ -12163,6 +12182,7 @@ pub const Unit = struct {
     main_package: ?*Package = null,
     all_errors: Type.Index = .null,
     descriptor: Descriptor,
+    object_files: UnpinnedArray([*:0]const u8) = .{},
     discard_identifiers: usize = 0,
     anon_i: usize = 0,
     anon_arr: usize = 0,
@@ -12885,6 +12905,20 @@ pub const Unit = struct {
         }
 
         if (!unit.descriptor.only_parse) {
+            try unit.object_files.ensure_capacity(context.my_allocator, @intCast(unit.descriptor.c_source_files.len));
+            for (unit.descriptor.c_source_files) |c_source_file| {
+                const c_src = span(c_source_file);
+                const dot_index = data_structures.last(c_src, '.') orelse unreachable;
+                const path_without_extension = c_src[0..dot_index];
+                const basename = std.fs.path.basename(path_without_extension);
+                const basename_z = try std.mem.joinZ(context.allocator, "/", &.{"nat", basename});
+                var c_flag = "-c".*;
+                var o_flag = "-o".*;
+                var arguments = [_][*:0]u8{&c_flag, c_source_file, &o_flag, basename_z};
+                try compileCSourceFile(context, &arguments);
+                unit.object_files.append_with_capacity(basename_z);
+            }
+
             try unit.analyze(context);
 
             try llvm.codegen(unit, context);
@@ -12938,6 +12972,7 @@ pub const Descriptor = struct {
     link_libc: bool,
     is_test: bool,
     generate_debug_information: bool,
+    c_source_files: []const [*:0]u8,
     name: []const u8,
 };
 
diff --git a/bootstrap/backend/llvm.zig b/bootstrap/backend/llvm.zig
index c8b56ec..b7e9bf5 100644
--- a/bootstrap/backend/llvm.zig
+++ b/bootstrap/backend/llvm.zig
@@ -3062,6 +3062,11 @@ pub fn codegen(unit: *Compilation.Unit, context: *const Compilation.Context) !vo
 
     try arguments.append(context.my_allocator, object_file_path.ptr);
 
+    try arguments.append_slice(context.my_allocator, unit.object_files.slice());
+    // for (unit.object_files.slice()) |object_file| {
+    //     _ = object_file; // autofix
+    // }
+
     switch (unit.descriptor.os) {
         .macos => {
             try arguments.append(context.my_allocator, "-dynamic");
@@ -3126,13 +3131,14 @@ pub fn codegen(unit: *Compilation.Unit, context: *const Compilation.Context) !vo
     }
 
     if (!linking_result) {
+        try write(.panic, "\n");
         for (arguments.slice()) |argument| {
             const arg = data_structures.span(argument);
-            try write(.llvm, arg);
-            try write(.llvm, " ");
+            try write(.panic, arg);
+            try write(.panic, " ");
         }
-        try write(.llvm, "\n");
+        try write(.panic, "\n");
 
-        @panic("Above linker invokation failed");
+        @panic(stderr_ptr[0..stderr_len]);
     }
 }
diff --git a/bootstrap/library.zig b/bootstrap/library.zig
index ac245ac..4b98986 100644
--- a/bootstrap/library.zig
+++ b/bootstrap/library.zig
@@ -723,3 +723,16 @@ pub fn span(ptr: [*:0]const u8) [:0]const u8 {
     }
     return ptr[0..len :0];
 }
+
+pub fn last(bytes: []const u8, byte: u8) ?usize {
+    var i = bytes.len;
+    while (i > 0)  {
+        i -= 1;
+
+        if (bytes[i] == byte) {
+            return i;
+        }
+    }
+
+    return null;
+}
diff --git a/bootstrap/main.zig b/bootstrap/main.zig
index 72d6b3d..f2eeb6c 100644
--- a/bootstrap/main.zig
+++ b/bootstrap/main.zig
@@ -29,10 +29,19 @@ pub export fn main(c_argc: c_int, c_argv: [*][*:0]c_char, c_envp: [*:null]?[*:0]
     if (entry_point(arguments)) |_| {
         return 0;
     } else |err| {
-        const error_name: []const u8 = @errorName(err);
-        Compilation.write(.panic, "Error: ") catch {};
-        Compilation.write(.panic, error_name) catch {};
-        Compilation.write(.panic, "\n") catch {};
+        const print_stack_trace = @import("configuration").print_stack_trace;
+        switch (print_stack_trace) {
+            true => if (@errorReturnTrace()) |trace| {
+                std.debug.dumpStackTrace(trace.*);
+            },
+            false => {
+                const error_name: []const u8 = @errorName(err);
+                Compilation.write(.panic, "Error: ") catch {};
+                Compilation.write(.panic, error_name) catch {};
+                Compilation.write(.panic, "\n") catch {};
+            },
+        }
+
         return 1;
     }
 }
diff --git a/lib/std/build.nat b/lib/std/build.nat
index fd9fc65..f8ad4f2 100644
--- a/lib/std/build.nat
+++ b/lib/std/build.nat
@@ -8,7 +8,7 @@ const Executable = struct{
     main_source_path: [:0]const u8,
     link_libc: bool = false,
     name: [:0]const u8,
-    c_source_files: []const []const u8 = .{}.&,
+    c_source_files: []const [:0]const u8 = .{}.&,
 
     const compile = fn(executable: Executable) *!void {
         const argument_count = std.start.argument_count;
@@ -35,8 +35,15 @@ const Executable = struct{
             } else {
                 link_libc_arg = "false";
             }
-            const argv = [_:null] ?[&:0]const u8{ compiler_path, "exe",  "-main_source_file", executable.main_source_path.ptr, "-link_libc", link_libc_arg, "-name", executable.name.ptr };
-            try std.os.execute(path = compiler_path, argv = argv.&, env = std.start.environment_values);
+
+            if (executable.c_source_files.len > 0) {
+                assert(executable.c_source_files.len == 1);
+                const argv = [_:null] ?[&:0]const u8{ compiler_path, "exe",  "-main_source_file", executable.main_source_path.ptr, "-link_libc", link_libc_arg, "-name", executable.name.ptr, "-c_source_files", executable.c_source_files[0].ptr };
+                try std.os.execute(path = compiler_path, argv = argv.&, env = std.start.environment_values);
+            } else {
+                const argv = [_:null] ?[&:0]const u8{ compiler_path, "exe",  "-main_source_file", executable.main_source_path.ptr, "-link_libc", link_libc_arg, "-name", executable.name.ptr };
+                try std.os.execute(path = compiler_path, argv = argv.&, env = std.start.environment_values);
+            }
         } else {
             const raw_status = try std.os.waitpid(pid, flags = 0);
             if (std.os.ifexited(status = raw_status)) {
diff --git a/lib/std/testing.nat b/lib/std/testing.nat
index d910872..289377e 100644
--- a/lib/std/testing.nat
+++ b/lib/std/testing.nat
@@ -2,7 +2,7 @@ const Error = error{
     unexpected_result,
 };
 
-const expect(ok: bool) Error!void {
+const expect = fn (ok: bool) Error!void {
     if (!ok) {
         return Error.unexpected_result;
     }
diff --git a/test/c-abi/first/build.nat b/test/build/c-abi/build.nat
similarity index 72%
rename from test/c-abi/first/build.nat
rename to test/build/c-abi/build.nat
index 5a3fda9..6afe512 100644
--- a/test/c-abi/first/build.nat
+++ b/test/build/c-abi/build.nat
@@ -1,5 +1,5 @@
 const std = #import("std");
-const build = std.build;
+const Executable  = std.build.Executable;
 
 const main = fn() *!void {
     const executable = Executable{
@@ -9,7 +9,8 @@ const main = fn() *!void {
             .abi = .gnu,
         },
         .main_source_path = "main.nat",
-        .name = "first",
+        .name = "c-abi",
+        .c_source_files = .{ "foo.c" }.&,
     };
 
     try executable.compile();
diff --git a/test/build/c-abi/foo.c b/test/build/c-abi/foo.c
new file mode 100644
index 0000000..6c420c2
--- /dev/null
+++ b/test/build/c-abi/foo.c
@@ -0,0 +1,5 @@
+typedef unsigned u32;
+u32 foo(u32 arg)
+{
+    return arg;
+}
diff --git a/test/c-abi/first/main.nat b/test/build/c-abi/main.nat
similarity index 81%
rename from test/c-abi/first/main.nat
rename to test/build/c-abi/main.nat
index e2d2017..2d7b711 100644
--- a/test/c-abi/first/main.nat
+++ b/test/build/c-abi/main.nat
@@ -1,5 +1,5 @@
 const std = #import("std");
-const expect = std.test.expect;
+const expect = std.testing.expect;
 const foo :: extern = fn(arg: u32) u32;
 const main = fn () *!void {
     const arg = 0xabcdef;