From b59565aa9b7396b36aa8a4e735823ca1f1852561 Mon Sep 17 00:00:00 2001
From: Gabriel Ferreira <gabrielcarvfer@gmail.com>
Date: Wed, 30 Nov 2022 12:35:51 -0300
Subject: [PATCH] build: add NS3_CCACHE and NS3_FAST_LINKERS switches to
 disable ccache and lld/mold usage

---
 CMakeLists.txt                             | 30 +++++++-----
 build-support/macros-and-definitions.cmake | 55 ++++++++++++----------
 2 files changed, 46 insertions(+), 39 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index f79f1e5b4..5a2dc9b75 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -3,19 +3,6 @@
 # ##############################################################################
 cmake_minimum_required(VERSION 3.10..3.10)
 
-# Use ccache if available
-mark_as_advanced(CCACHE)
-find_program(CCACHE ccache)
-if(NOT ("${CCACHE}" STREQUAL "CCACHE-NOTFOUND"))
-  message(STATUS "CCache is enabled.")
-  set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE ${CCACHE})
-  execute_process(
-    COMMAND
-      ${CCACHE} --set-config
-      sloppiness=pch_defines,time_macros,include_file_mtime,include_file_ctime
-  )
-endif()
-
 # ##############################################################################
 # Project name                        #
 # ##############################################################################
@@ -66,6 +53,8 @@ option(NS3_NETANIM "Build netanim" OFF)
 
 # other options
 option(NS3_ENABLE_BUILD_VERSION "Embed version info into libraries" OFF)
+option(NS3_CCACHE "Use Ccache to speed up recompilation" ON)
+option(NS3_FAST_LINKERS "Use Mold or LLD to speed up linking if available" ON)
 option(NS3_GSL "Build with GSL support" ON)
 option(NS3_GTK3 "Build with GTK3 support" ON)
 option(NS3_LINK_TIME_OPTIMIZATION "Build with link-time optimization" OFF)
@@ -111,6 +100,21 @@ set(NS3_FILTER_MODULE_EXAMPLES_AND_TESTS
       "List of modules that should have their examples and tests built (e.g. lte;wifi)"
 )
 
+if(${NS3_CCACHE})
+  # Use ccache if available
+  mark_as_advanced(CCACHE)
+  find_program(CCACHE ccache)
+  if(NOT ("${CCACHE}" STREQUAL "CCACHE-NOTFOUND"))
+    message(STATUS "CCache is enabled.")
+    set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE ${CCACHE})
+    execute_process(
+      COMMAND
+        ${CCACHE} --set-config
+        sloppiness=pch_defines,time_macros,include_file_mtime,include_file_ctime
+    )
+  endif()
+endif()
+
 # Include macros used below
 include(build-support/macros-and-definitions.cmake)
 
diff --git a/build-support/macros-and-definitions.cmake b/build-support/macros-and-definitions.cmake
index 4da5f7323..4a6f9ff26 100644
--- a/build-support/macros-and-definitions.cmake
+++ b/build-support/macros-and-definitions.cmake
@@ -240,33 +240,35 @@ if(${CLANG} AND APPLE)
   set(STATIC_LINK_FLAGS)
 endif()
 
-# Search for faster linkers mold and lld, and use them if available
-mark_as_advanced(MOLD LLD)
-find_program(MOLD mold)
-find_program(LLD ld.lld)
+if(${NS3_FAST_LINKERS})
+  # Search for faster linkers mold and lld, and use them if available
+  mark_as_advanced(MOLD LLD)
+  find_program(MOLD mold)
+  find_program(LLD ld.lld)
 
-# USING_FAST_LINKER will be defined if a fast linker is being used and its
-# content will correspond to the fast linker name
+  # USING_FAST_LINKER will be defined if a fast linker is being used and its
+  # content will correspond to the fast linker name
 
-# Mold support was added in GCC 12.1.0
-if(NOT USING_FAST_LINKER
-   AND NOT (${MOLD} STREQUAL "MOLD-NOTFOUND")
-   AND LINUX
-   AND ${GCC}
-   AND (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 12.1.0)
-)
-  set(USING_FAST_LINKER MOLD)
-  add_link_options("-fuse-ld=mold")
-endif()
+  # Mold support was added in GCC 12.1.0
+  if(NOT USING_FAST_LINKER
+     AND NOT (${MOLD} STREQUAL "MOLD-NOTFOUND")
+     AND LINUX
+     AND ${GCC}
+     AND (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 12.1.0)
+  )
+    set(USING_FAST_LINKER MOLD)
+    add_link_options("-fuse-ld=mold")
+  endif()
 
-if(NOT USING_FAST_LINKER AND NOT (${LLD} STREQUAL "LLD-NOTFOUND")
-   AND (${GCC} OR ${CLANG})
-)
-  set(USING_FAST_LINKER LLD)
-  add_link_options("-fuse-ld=lld")
-  if(WIN32)
-    # Clear unsupported linker flags on Windows
-    set(LIB_AS_NEEDED_PRE)
+  if(NOT USING_FAST_LINKER AND NOT (${LLD} STREQUAL "LLD-NOTFOUND")
+     AND (${GCC} OR ${CLANG})
+  )
+    set(USING_FAST_LINKER LLD)
+    add_link_options("-fuse-ld=lld")
+    if(WIN32)
+      # Clear unsupported linker flags on Windows
+      set(LIB_AS_NEEDED_PRE)
+    endif()
   endif()
 endif()
 
@@ -1331,8 +1333,9 @@ macro(process_options)
         "Clang-tidy is incompatible with precompiled headers. Continuing without them."
       )
     elseif(${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.16.0")
-      # If ccache was not found, we can continue with precompiled headers
-      if("${CCACHE}" STREQUAL "CCACHE-NOTFOUND")
+      # If ccache is not enable or was not found, we can continue with
+      # precompiled headers
+      if((NOT ${NS3_CCACHE}) OR ("${CCACHE}" STREQUAL "CCACHE-NOTFOUND"))
         set(PRECOMPILE_HEADERS_ENABLED ON)
         message(STATUS "Precompiled headers were enabled")
       else()