diff --git a/CMakeLists.txt b/CMakeLists.txt
index ffb422e..d2211d6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.5)
-project(photon)
+project(photon C ASM-ATT)
 
 macro(subdirlist result curdir)
     file(GLOB children RELATIVE ${curdir} ${curdir}/*)
@@ -36,18 +36,37 @@ endif ()
 
 message(STATUS "Target platform: ${PLATFORM}")
 
+set(CMAKE_EXE_LINKER_FLAGS
+    "${CMAKE_EXE_LINKER_FLAGS} -ffreestanding -nostdlib -lgcc")
+
 set(photon_libc_sources "")
-set(generic_dirs string include)
+set(generic_dirs string)
 
 foreach (dir ${generic_dirs})
-    file(GLOB_RECURSE dir_sources ${CMAKE_CURRENT_SOURCE_DIR}/photon/libc/${dir}/*.c)
+    file(GLOB dir_sources ${CMAKE_CURRENT_SOURCE_DIR}/photon/libc/${dir}/*.c)
     set(photon_libc_sources ${photon_libc_sources} ${dir_sources})
 endforeach (dir)
 
-file(GLOB_RECURSE platform_sources ${CMAKE_CURRENT_SOURCE_DIR}/photon/sys/${PLATFORM})
+file(GLOB_RECURSE photon_libc_includes ${CMAKE_CURRENT_SOURCE_DIR}/photon/libc/include/*.h)
+
+file(GLOB photon_libc_crt
+    ${CMAKE_CURRENT_SOURCE_DIR}/photon/libc/sys/${PLATFORM}/machine/${MACHINE}/crt*.s)
+
+add_library(crt OBJECT ${photon_libc_crt})
+message(STATUS "CRT sources: ${photon_libc_crt}")
+
+file(GLOB platform_sources
+    ${CMAKE_CURRENT_SOURCE_DIR}/photon/sys/${PLATFORM}/*.c
+    ${CMAKE_CURRENT_SOURCE_DIR}/photon/sys/${PLATFORM}/*.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/photon/sys/${PLATFORM}/machine/${MACHINE}/*.c
+    ${CMAKE_CURRENT_SOURCE_DIR}/photon/sys/${PLATFORM}/machine/${MACHINE}/*.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/photon/sys/${PLATFORM}/machine/${MACHINE}/*.s)
 set(photon_libc_sources ${photon_libc_sources} ${platform_sources})
 
-add_library(c STATIC ${photon_libc_sources})
+add_library(c STATIC ${photon_libc_sources} ${photon_libc_includes})
 target_compile_options(c PRIVATE -ffreestanding -nostdlib -nostdinc)
+target_link_libraries(c crt)
 
 target_include_directories(c PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/photon/libc/include)
+
+add_subdirectory(tests)
diff --git a/photon/libc/include/machine/_stdint.h b/photon/libc/include/machine/_stdint.h
index 7dcf5b1..4a510ed 100644
--- a/photon/libc/include/machine/_stdint.h
+++ b/photon/libc/include/machine/_stdint.h
@@ -14,9 +14,9 @@
 #define __have_long32 1
 #endif
 
-#ifdef __cplusplus
+#if defined(__cplusplus)
 extern "C" {
-#endif
+#endif /* defined(__cplusplus) */
 
 #ifdef __INT8_TYPE__
 typedef __INT8_TYPE__ __int8_t;
@@ -236,8 +236,8 @@ typedef __uint64_t __uint_fast64_t;
 
 #undef __EXP
 
-#ifdef __cplusplus
+#if defined(__cplusplus)
 }
-#endif
+#endif /* defined(__cplusplus) */
 
 #endif /* _MACHINE__STDINT_H */
diff --git a/photon/libc/include/stddef.h b/photon/libc/include/stddef.h
index 87509ea..270be52 100644
--- a/photon/libc/include/stddef.h
+++ b/photon/libc/include/stddef.h
@@ -8,7 +8,7 @@
 
 #if defined(__cplusplus)
 extern "C" {
-#endif
+#endif /* defined(__cplusplus) */
 
 typedef __intptr_t ptrdiff_t;
 typedef __uintptr_t size_t;
@@ -16,6 +16,6 @@ typedef int wchar_t;
 
 #if defined(__cplusplus)
 }
-#endif
+#endif /* defined(__cplusplus) */
 
-#endif
+#endif /* STDDEF_H_ */
diff --git a/photon/libc/include/stdint.h b/photon/libc/include/stdint.h
index 361107c..117785c 100644
--- a/photon/libc/include/stdint.h
+++ b/photon/libc/include/stdint.h
@@ -50,4 +50,4 @@ typedef __uintptr_t uintptr_t;
 
 typedef
 
-#endif
+#endif /* STDINT_H_ */
diff --git a/photon/libc/machine/i386/types.h b/photon/libc/machine/i386/types.h
deleted file mode 100644
index e69de29..0000000
diff --git a/photon/libc/sys/linux/machine/x86_64/crt0.s b/photon/libc/sys/linux/machine/x86_64/crt0.s
new file mode 100644
index 0000000..36292af
--- /dev/null
+++ b/photon/libc/sys/linux/machine/x86_64/crt0.s
@@ -0,0 +1,15 @@
+.global _start
+.type _start, @function
+
+.extern main
+.type main, @function
+
+_start:
+    pop %rbp
+    pop %rdi
+    mov %rsp, %rsi
+    andq $-16, %rsp
+    call main
+    movq %rax, %rdi
+    movq $60, %rax
+    syscall
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
new file mode 100644
index 0000000..2402243
--- /dev/null
+++ b/tests/CMakeLists.txt
@@ -0,0 +1,8 @@
+file(GLOB test_sources ${CMAKE_CURRENT_SOURCE_DIR}/*.c)
+
+foreach (test ${test_sources})
+    get_filename_component(test_name ${test} NAME_WE)
+    add_executable(${test_name} ${test} $<TARGET_OBJECTS:crt>)
+    target_compile_options(${test_name} PRIVATE -ffreestanding -nostdlib -nostdinc)
+    target_link_libraries(${test_name} c)
+endforeach (test)
diff --git a/tests/start.c b/tests/start.c
new file mode 100644
index 0000000..c006f23
--- /dev/null
+++ b/tests/start.c
@@ -0,0 +1,4 @@
+int main(int argc, char **argv)
+{
+    return 42;
+}