[libc-commits] [libc] [libc] Add base for target config within cmake (PR #72318)

[via libc-commits]

https://github.com/michaelrj-google created https://github.com/llvm/llvm-project/pull/72318

Currently the only way to add or remove entrypoints is to modify the
entrypoints.txt file for the current target. This isn't ideal since
a user would have to carry a diff for this file when updating their
checkout. This patch adds a basic mechanism to allow the user to remove
entrypoints without modifying the repository. 


>From f89b89f843bdc862227f2a39ff7a0beb61f43f03 Mon Sep 17 00:00:00 2001
From: Michael Jones <michaelrj at google.com>
Date: Tue, 14 Nov 2023 14:11:42 -0800
Subject: [PATCH] [libc] Add base for target config within cmake

Currently the only way to add or remove entrypoints is to modify the
entrypoints.txt file for the current target. This isn't ideal since
a user would have to carry a diff for this file when updating their
checkout. This patch adds a basic mechanism to allow the user to remove
entrypoints without modifying the repository.
---
 libc/CMakeLists.txt        | 21 +++++++++++++++++++++
 libc/config/CMakeLists.txt |  2 ++
 2 files changed, 23 insertions(+)

diff --git a/libc/CMakeLists.txt b/libc/CMakeLists.txt
index 414be906336bf3f..922209eee8e2edd 100644
--- a/libc/CMakeLists.txt
+++ b/libc/CMakeLists.txt
@@ -103,6 +103,8 @@ option(LLVM_LIBC_ENABLE_LINTING "Enables linting of libc source files" OFF)
 option(LIBC_GPU_BUILD "Build libc for the GPU. All CPU build options will be ignored." OFF)
 set(LIBC_TARGET_TRIPLE "" CACHE STRING "The target triple for the libc build.")
 
+option(LIBC_SYSTEM_CONFIG_FILE "The path to user provided cmake file that configures the build for the target system." OFF)
+
 set(LIBC_ENABLE_UNITTESTS ON)
 set(LIBC_ENABLE_HERMETIC_TESTS ${LLVM_LIBC_FULL_BUILD})
 
@@ -262,6 +264,25 @@ elseif(EXISTS "${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/headers.txt")
   include("${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/headers.txt")
 endif()
 
+if(LIBC_SYSTEM_CONFIG_FILE)
+  if(EXISTS "${LIBC_SYSTEM_CONFIG_FILE}")
+    include("${LIBC_SYSTEM_CONFIG_FILE}")
+  else()
+    message(FATAL_ERROR "System Config File set to unavailable file '${LIBC_SYSTEM_CONFIG_FILE}'")
+  endif()
+
+  #TODO: Set up support for premade configs.
+
+  foreach(removed_entrypoint IN LISTS TARGET_LLVMLIBC_REMOVED_ENTRYPOINTS)
+    if(LIBC_CMAKE_VERBOSE_LOGGING)
+      message(STATUS "Removing entrypoint ${removed_entrypoint}")
+    endif()
+    list(REMOVE_ITEM TARGET_LLVMLIBC_ENTRYPOINTS ${removed_entrypoint})
+    list(REMOVE_ITEM TARGET_LIBC_ENTRYPOINTS ${removed_entrypoint})
+    list(REMOVE_ITEM TARGET_LIBM_ENTRYPOINTS ${removed_entrypoint})
+  endforeach()
+endif()
+
 set(TARGET_ENTRYPOINT_NAME_LIST "")
 foreach(entrypoint IN LISTS TARGET_LLVMLIBC_ENTRYPOINTS)
   string(FIND ${entrypoint} "." last_dot_loc REVERSE)
diff --git a/libc/config/CMakeLists.txt b/libc/config/CMakeLists.txt
index a1034f9954740fe..853854b03be4e4e 100644
--- a/libc/config/CMakeLists.txt
+++ b/libc/config/CMakeLists.txt
@@ -1 +1,3 @@
+#TODO: Properly select the correct subdirectory.
+
 add_subdirectory(linux)