Add zlib as dependency for examples

Similar to what the Bazel build does, this change adds zlib as an additional
dependency when `SAPI_ENABLE_EXAMPLES` is set to `ON`.

PiperOrigin-RevId: 309203959
Change-Id: I201a9e6415789afb1e058bc48cebbc0fc0004fe9

cmake/SapiDeps.cmake

@@ -81,7 +81,12 @@ else()
 endif()
 
 if(SAPI_ENABLE_EXAMPLES)
+  if(SAPI_DOWNLOAD_ZLIB)
+    include(cmake/zlib/Download.cmake)
+    check_target(ZLIB::ZLIB)
+  else()
     find_package(ZLIB REQUIRED)
+  endif()
 endif()
 
 # Find Python 3 and add its location to the cache so that its available in

cmake/SapiOptions.cmake

@@ -29,5 +29,8 @@ option(SAPI_DOWNLOAD_LIBUNWIND "Download libunwind at config time" ON)
 option(SAPI_DOWNLOAD_LIBCAP "Download libcap at config time" ON)
 option(SAPI_DOWNLOAD_LIBFFI "Download libffi at config time" ON)
 
+# Options for building examples
 option(SAPI_ENABLE_EXAMPLES "Build example code" ON)
+option(SAPI_DOWNLOAD_ZLIB "Download zlib at config time (only if SAPI_ENABLE_EXAMPLES is set)" ON)
+
 option(SAPI_ENABLE_TESTS "Build unit tests" ON)

cmake/zlib/CMakeLists.txt.in

@@ -0,0 +1,30 @@
+# Copyright 2020 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+cmake_minimum_required(VERSION 3.12)
+project(zlib-download NONE)
+
+include(ExternalProject)
+ExternalProject_Add(zlib
+  URL https://mirror.bazel.build/zlib.net/zlib-1.2.11.tar.gz
+  URL_HASH SHA256=c3e5e9fdd5004dcb542feda5ee4f0ff0744628baf8ed2dd5d66f8ca1197cb1a1  # 2020-04-23
+  SOURCE_DIR        "${CMAKE_BINARY_DIR}/zlib-src"
+  PATCH_COMMAND     patch -p1
+                    < "${CMAKE_SOURCE_DIR}/sandboxed_api/bazel/external/zlib.patch"
+  CONFIGURE_COMMAND ""
+  BUILD_COMMAND     ""
+  INSTALL_COMMAND   ""
+  TEST_COMMAND      ""
+  BUILD_IN_SOURCE TRUE
+)

cmake/zlib/Download.cmake

@@ -0,0 +1,77 @@
+# Copyright 2020 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Downloads and unpacks Abseil at configure time
+
+set(workdir "${CMAKE_BINARY_DIR}/zlib-download")
+
+configure_file("${CMAKE_CURRENT_LIST_DIR}/CMakeLists.txt.in"
+               "${workdir}/CMakeLists.txt")
+execute_process(COMMAND ${CMAKE_COMMAND} -G "${CMAKE_GENERATOR}" .
+                RESULT_VARIABLE error
+                WORKING_DIRECTORY "${workdir}")
+if(error)
+  message(FATAL_ERROR "CMake step for ${PROJECT_NAME} failed: ${error}")
+endif()
+
+execute_process(COMMAND ${CMAKE_COMMAND} --build .
+                RESULT_VARIABLE error
+                WORKING_DIRECTORY "${workdir}")
+if(error)
+  message(FATAL_ERROR "Build step for ${PROJECT_NAME} failed: ${error}")
+endif()
+
+set(_zlib_src "${CMAKE_BINARY_DIR}/zlib-src")
+
+set(ZLIB_INCLUDE_DIRS ${_zlib_src})
+
+add_library(z STATIC
+  ${_zlib_src}/adler32.c
+  ${_zlib_src}/compress.c
+  ${_zlib_src}/crc32.c
+  ${_zlib_src}/crc32.h
+  ${_zlib_src}/deflate.c
+  ${_zlib_src}/deflate.h
+  ${_zlib_src}/gzclose.c
+  ${_zlib_src}/gzguts.h
+  ${_zlib_src}/gzlib.c
+  ${_zlib_src}/gzread.c
+  ${_zlib_src}/gzwrite.c
+  ${_zlib_src}/infback.c
+  ${_zlib_src}/inffast.c
+  ${_zlib_src}/inffast.h
+  ${_zlib_src}/inffixed.h
+  ${_zlib_src}/inflate.c
+  ${_zlib_src}/inflate.h
+  ${_zlib_src}/inftrees.c
+  ${_zlib_src}/inftrees.h
+  ${_zlib_src}/trees.c
+  ${_zlib_src}/trees.h
+  ${_zlib_src}/uncompr.c
+  ${_zlib_src}/zconf.h
+  ${_zlib_src}/zlib.h
+  ${_zlib_src}/zutil.c
+  ${_zlib_src}/zutil.h
+)
+add_library(ZLIB::ZLIB ALIAS z)
+target_include_directories(z PUBLIC
+  ${_zlib_src}
+)
+target_compile_options(z PRIVATE
+  -w
+  -Dverbose=-1
+)
+target_link_libraries(z PRIVATE
+  sapi::base
+)

sandboxed_api/examples/CMakeLists.txt

@@ -15,4 +15,5 @@
 if(SAPI_ENABLE_EXAMPLES)
   add_subdirectory(stringop)
   add_subdirectory(sum)
+  add_subdirectory(zlib)
 endif()

sandboxed_api/examples/zlib/CMakeLists.txt

@@ -0,0 +1,42 @@
+# Copyright 2020 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# sandboxed_api/examples/zlib:zlib-sapi
+add_sapi_library(zlib-sapi
+  FUNCTIONS deflateInit_
+            deflate
+            deflateEnd
+  INPUTS ${ZLIB_INCLUDE_DIRS}/zlib.h
+  LIBRARY ZLIB::ZLIB
+  LIBRARY_NAME Zlib
+  NAMESPACE "sapi::zlib"
+)
+add_library(sapi::zlib_sapi ALIAS zlib-sapi)
+target_link_libraries(zlib-sapi PRIVATE
+  ZLIB::ZLIB
+)
+
+# sandboxed_api/examples/zlib:main_zlib
+add_executable(main_zlib
+  main_zlib.cc
+)
+target_link_libraries(main_zlib PRIVATE
+  sapi::base
+  glog::glog
+  sapi::flags
+  sapi::sapi
+  sapi::status
+  sapi::statusor
+  sapi::zlib_sapi
+)

sandboxed_api/sandbox2/examples/zlib/CMakeLists.txt

@@ -37,5 +37,4 @@ add_executable(zpipe
 add_executable(sandbox2::zpipe ALIAS zpipe)
 target_link_libraries(zpipe PRIVATE
   ZLIB::ZLIB
-  -static  # Fully static link
 )