[libc] Move all tests to a top level `test` directory.

[sivachandra]

Summary

A toplevel target, check-libc has also been added.

[sivachandra]

This change is implementing the proposal I made in http://lists.llvm.org/pipermail/libc-dev/2019-December/000030.html

[sivachandra]

Thanks for the review. I have now pushed this change.

libc/CMakeLists.txt

 set(LIBC_TARGET_MACHINE ${CMAKE_SYSTEM_PROCESSOR})
 
 include(CMakeParseArguments)
 include(LLVMLibCRules)
 
 add_subdirectory(src)
 add_subdirectory(config)
 add_subdirectory(include)
-add_subdirectory(lib)
 add_subdirectory(utils)
+
+# The lib and test directories are added at the very end as tests
+# and libraries potentially draw from the components present in all
+# of the other directories.
+add_subdirectory(lib)
+add_subdirectory(test)

libc/config/linux/x86_64/CMakeLists.txt

-add_custom_target(libc_linux_x86_64_unittests)
-
-add_libc_unittest(
-  libc_linux_x86_64_syscall_unittest
-  SUITE libc_linux_x86_64_unittests
-  SRCS syscall_test.cpp
-  DEPENDS
-   syscall_impl_h
-   support_common_h
-)

libc/docs/source_layout.rst

 LLVM-libc Source Tree Layout
 ============================
 
 At the top-level, LLVM-libc source tree is organized in to the following
 directories::
 
    + libc
         - cmake
         - docs
         - include
         - lib
         - loader
         - src
+        - test
         + utils
             - build_scripts
             - testing
         - www
 
 Each of these directories is explained in detail below.
 
 The ``cmake`` directory

 1. There is a toplevel CMakeLists.txt file.
 2. For every public header file provided by llvm-libc, there exists a
    corresponding directory in the ``src`` directory. The name of the directory
    is same as the base name of the header file. For example, the directory
    corresponding to the public ``math.h`` header file is named ``math``. The
    implementation standard document explains more about the *header*
    directories.
 
+The ``test`` directory
+----------------------
+
+This directory contains tests for the various components of llvm-libc. The
+directory structure within this directory mirrors the directory structure of the
+toplevel ``libc`` directory itself. A test for, say the ``mmap`` function, lives
+in the directory ``test/src/sys/mman/`` as implementation of ``mmap`` lives in
+``src/sys/mman``.
+
 The ``www`` directory
 ---------------------
 
 The ``www`` directory contains the HTML content of libc.llvm.org
 
 The ``utils/build_scripts`` directory
 -------------------------------------
 
 This directory contains scripts which support the build system, tooling etc.
 
 The ``utils/testing`` directory
 -------------------------------
 
 This directory contains testing infrastructure.

libc/src/errno/CMakeLists.txt

 add_entrypoint_object(
   __errno_location
   SRCS
     errno_location.cpp
   HDRS
     llvmlibc_errno.h
 )
-
-add_custom_target(libc_errno_unittests)
-
-add_libc_unittest(
-  errno_test
-  SUITE
-    libc_errno_unittests
-  SRCS
-    errno_test.cpp
-  DEPENDS
-    __errno_location
-)

libc/src/string/CMakeLists.txt

-add_custom_target(libc_string_unittests)
-
 add_subdirectory(strcpy)
 add_subdirectory(strcat)

libc/src/string/strcat/CMakeLists.txt

 add_entrypoint_object(
   strcat
   SRCS
     strcat.cpp
   HDRS
     strcat.h
   DEPENDS
     strcpy
     string_h
 )
-
-add_libc_unittest(
-  strcat_test
-  SUITE
-    libc_string_unittests
-  SRCS
-    strcat_test.cpp
-  DEPENDS
-    strcat
-    strcpy
-)

libc/src/string/strcpy/CMakeLists.txt

 add_entrypoint_object(
   strcpy
   SRCS
     strcpy.cpp
   HDRS
     strcpy.h
   DEPENDS
     string_h
 )
-
-add_libc_unittest(
-  strcpy_test
-  SUITE
-    libc_string_unittests
-  SRCS
-    strcpy_test.cpp
-  DEPENDS
-    strcpy
-)

libc/src/sys/mman/CMakeLists.txt

add_entrypoint_object(
   HDRS
     munmap.h
   DEPENDS
     sys_mman_h
     sys_syscall_h
     syscall_impl_h
     __errno_location
 )
-
-add_custom_target(libc_sys_mman_unittests)
-
-add_libc_unittest(
-  mmap_test
-  SUITE
-    libc_sys_mman_unittests
-  SRCS
-    mmap_test.cpp
-  DEPENDS
-    mmap
-    munmap
-    __errno_location
-)

libc/test/CMakeLists.txt

+add_custom_target(check_libc)
+
+add_subdirectory(config)
+add_subdirectory(src)

libc/test/config/CMakeLists.txt

+add_subdirectory(linux)

libc/test/config/linux/CMakeLists.txt

+add_custom_target(libc_linux_tests)
+add_dependencies(check_libc libc_linux_tests)
+
+add_subdirectory(x86_64)

libc/test/config/linux/x86_64/CMakeLists.txt

+add_custom_target(libc_linux_x86_64_tests)
+add_dependencies(libc_linux_tests libc_linux_x86_64_tests)
+
+add_libc_unittest(
+  libc_linux_x86_64_syscall_unittest
+  SUITE libc_linux_x86_64_tests
+  SRCS syscall_test.cpp
+  DEPENDS
+   syscall_impl_h
+   support_common_h
+)

libc/test/src/CMakeLists.txt

+add_subdirectory(errno)
+add_subdirectory(string)
+add_subdirectory(sys)

libc/test/src/errno/CMakeLists.txt

-add_entrypoint_object(
-  __errno_location
-  SRCS
-    errno_location.cpp
-  HDRS
-    llvmlibc_errno.h
-)
-
 add_custom_target(libc_errno_unittests)
+add_dependencies(check_libc libc_errno_unittests)
 
 add_libc_unittest(
   errno_test
   SUITE
     libc_errno_unittests
   SRCS
     errno_test.cpp
   DEPENDS
     __errno_location
 )

libc/test/src/string/CMakeLists.txt

+add_custom_target(libc_string_unittests)
+add_dependencies(check_libc libc_string_unittests)
+
+add_libc_unittest(
+  strcat_test
+  SUITE
+    libc_string_unittests
+  SRCS
+    strcat_test.cpp
+  DEPENDS
+    strcat
+    strcpy
+)
+
+add_libc_unittest(
+  strcpy_test
+  SUITE
+    libc_string_unittests
+  SRCS
+    strcpy_test.cpp
+  DEPENDS
+    strcpy
+)

libc/test/src/sys/CMakeLists.txt

+add_subdirectory(mman)

libc/test/src/sys/mman/CMakeLists.txt

+add_custom_target(libc_sys_mman_unittests)
+add_dependencies(check_libc libc_sys_mman_unittests)
+
+add_libc_unittest(
+  mmap_test
+  SUITE
+    libc_sys_mman_unittests
+  SRCS
+    mmap_test.cpp
+  DEPENDS
+    mmap
+    munmap
+    __errno_location
+)