From 61ee6e26b562f181c2b3f9a6232e6a438640b743 Mon Sep 17 00:00:00 2001
From: Matthias Maier <tamiko@43-1.org>
Date: Fri, 2 Dec 2022 22:04:05 -0600
Subject: [PATCH] CMake: remove DEAL_II_SETUP_DEFAULT_COMPILER_FLAGS configure
 option

---
 cmake/setup_cached_variables.cmake |  7 ------
 cmake/setup_compiler_flags.cmake   | 40 ++++++++----------------------
 cmake/setup_write_config.cmake     |  3 ---
 doc/developers/porting.html        |  3 +--
 doc/users/cmake_dealii.html        | 22 ++++++----------
 doc/users/config.sample            |  1 -
 6 files changed, 19 insertions(+), 57 deletions(-)

diff --git a/cmake/setup_cached_variables.cmake b/cmake/setup_cached_variables.cmake
index fd690594b4..91a58bd8b6 100644
--- a/cmake/setup_cached_variables.cmake
+++ b/cmake/setup_cached_variables.cmake
@@ -32,7 +32,6 @@
 #
 #     CMAKE_BUILD_TYPE
 #     DEAL_II_ALLOW_PLATFORM_INTROSPECTION
-#     DEAL_II_SETUP_DEFAULT_COMPILER_FLAGS
 #     DEAL_II_SETUP_COVERAGE
 #     DEAL_II_UNITY_BUILD
 #     DEAL_II_EARLY_DEPRECATIONS
@@ -153,12 +152,6 @@ option(DEAL_II_ALLOW_PLATFORM_INTROSPECTION
   )
 mark_as_advanced(DEAL_II_ALLOW_PLATFORM_INTROSPECTION)
 
-option(DEAL_II_SETUP_DEFAULT_COMPILER_FLAGS
-  "Configure sensible default CFLAGS and CXXFLAGS depending on platform, compiler and build target."
-  ON
-  )
-mark_as_advanced(DEAL_II_SETUP_DEFAULT_COMPILER_FLAGS)
-
 option(DEAL_II_SETUP_COVERAGE
   "Setup debug compiler flags to provide additional test coverage information. Currently only gprof is supported."
   OFF
diff --git a/cmake/setup_compiler_flags.cmake b/cmake/setup_compiler_flags.cmake
index 4f9a8e762b..04c7ba9836 100644
--- a/cmake/setup_compiler_flags.cmake
+++ b/cmake/setup_compiler_flags.cmake
@@ -97,48 +97,28 @@ endforeach()
 #                                                                      #
 ########################################################################
 
-if(DEAL_II_SETUP_DEFAULT_COMPILER_FLAGS)
-  #
-  # *Hooray* We are allowed to set compiler flags :-]
-  #
-
+if( CMAKE_CXX_COMPILER_ID MATCHES "GNU" OR
+    CMAKE_CXX_COMPILER_ID MATCHES "Clang" )
   #
   # General setup for GCC and compilers sufficiently close to GCC:
   #
-  if( CMAKE_CXX_COMPILER_ID MATCHES "GNU" OR
-      CMAKE_CXX_COMPILER_ID MATCHES "Clang" )
-    verbose_include(${CMAKE_SOURCE_DIR}/cmake/setup_compiler_flags_gnu.cmake)
-    set(DEAL_II_KNOWN_COMPILER TRUE)
-  endif()
+  verbose_include(${CMAKE_SOURCE_DIR}/cmake/setup_compiler_flags_gnu.cmake)
 
+elseif(CMAKE_CXX_COMPILER_ID MATCHES "Intel")
   #
   # Setup for ICC compiler (version >= 10):
   #
-  if(CMAKE_CXX_COMPILER_ID MATCHES "Intel")
-    verbose_include(${CMAKE_SOURCE_DIR}/cmake/setup_compiler_flags_intel.cmake)
-    set(DEAL_II_KNOWN_COMPILER TRUE)
-  endif()
+  verbose_include(${CMAKE_SOURCE_DIR}/cmake/setup_compiler_flags_intel.cmake)
 
+elseif(CMAKE_CXX_COMPILER_ID MATCHES "MSVC")
   #
   # Setup for MSVC compiler (version >= 2012):
   #
-   if(CMAKE_CXX_COMPILER_ID MATCHES "MSVC")
-    verbose_include(${CMAKE_SOURCE_DIR}/cmake/setup_compiler_flags_msvc.cmake)
-    set(DEAL_II_KNOWN_COMPILER TRUE)
-  endif()
-
-  if(NOT DEAL_II_KNOWN_COMPILER)
-    message(FATAL_ERROR "\n"
-      "Unknown compiler!\n"
-      "If you're serious about it, set DEAL_II_SETUP_DEFAULT_COMPILER_FLAGS=OFF "
-      "and set the relevant compiler options by hand.\n\n"
-      )
-  endif()
+  verbose_include(${CMAKE_SOURCE_DIR}/cmake/setup_compiler_flags_msvc.cmake)
 
 else()
-
-  message(STATUS
-    "Skipped setup of default compiler flags "
-    "(DEAL_II_SETUP_DEFAULT_COMPILER_FLAGS=OFF)"
+  message(WARNING "\nUnknown compiler!\n"
+    "Please populate the CMake variables DEAL_II_CXX_FLAGS(|DEBUG|RELEASE) "
+    "and DEAL_II_LINKER_FLAGS(|DEBUG|RELEASE) as needed."
     )
 endif()
diff --git a/cmake/setup_write_config.cmake b/cmake/setup_write_config.cmake
index 4a639402b2..379f051279 100644
--- a/cmake/setup_write_config.cmake
+++ b/cmake/setup_write_config.cmake
@@ -162,9 +162,6 @@ endif()
 
 _detailed("#\n")
 
-if(NOT DEAL_II_SETUP_DEFAULT_COMPILER_FLAGS)
-  _both("#  WARNING: DEAL_II_SETUP_DEFAULT_COMPILER_FLAGS is set to OFF\n")
-endif()
 _both("#  Configured Features (")
 if(DEFINED DEAL_II_ALLOW_BUNDLED)
   _both("DEAL_II_ALLOW_BUNDLED = ${DEAL_II_ALLOW_BUNDLED}, ")
diff --git a/doc/developers/porting.html b/doc/developers/porting.html
index 1df58d12b8..bb71a6a570 100644
--- a/doc/developers/porting.html
+++ b/doc/developers/porting.html
@@ -35,8 +35,7 @@
       sets up reasonable default compiler flags.
       <ul>
         <li>
-          To start porting to an unknown compiler, specify
-          <code>-DDEAL_II_SETUP_DEFAULT_COMPILER_FLAGS=OFF</code> and set all
+          To start porting to an unknown compiler, specify all
           necessary compiler flags by hand via
 <pre>
 DEAL_II_CXX_FLAGS         - used during all builds
diff --git a/doc/users/cmake_dealii.html b/doc/users/cmake_dealii.html
index ee0cf813f9..c4120ba691 100644
--- a/doc/users/cmake_dealii.html
+++ b/doc/users/cmake_dealii.html
@@ -836,9 +836,9 @@ cmake -DCMAKE_C_COMPILER=my_c_compiler -DCMAKE_CXX_COMPILER=my_cxx_compiler -DCM
       target. There are two options to override this behaviour:
 
       <ol>
-	<li>
-	  Override the default configuration by setting the following
-	  cached variables:
+        <li>
+          Override the default configuration by setting the following
+          cached variables:
 <pre class="cmake">
 DEAL_II_CXX_FLAGS         - used during all builds
 DEAL_II_CXX_FLAGS_DEBUG   - additional flags for the debug library
@@ -849,11 +849,11 @@ DEAL_II_LINKER_FLAGS_DEBUG   - additional flags for the debug library
 DEAL_II_LINKER_FLAGS_RELEASE - additional flags for the release library
 </pre>
 
-	  The content of the cached variables will be preserved
-	  and added <i>to the end</i> of the default compiler flags,
-	  hence providing the possibility for overriding a flag. E.g.:
-	  <code>-Wsign-compare</code>, set by the build system, can be
-	  overwritten by specifying:
+          The content of the cached variables will be preserved
+          and added <i>to the end</i> of the default compiler flags,
+          hence providing the possibility for overriding a flag. E.g.:
+          <code>-Wsign-compare</code>, set by the build system, can be
+          overwritten by specifying:
 <pre class="cmake">
 cmake -DDEAL_II_CXX_FLAGS="-Wno-sign-compare" &lt;...&gt;
 </pre>
@@ -864,12 +864,6 @@ cmake -DDEAL_II_CXX_FLAGS="-Wno-sign-compare" &lt;...&gt;
           variables will also be appended after the default compiler flags
           (but before the corresponding cached variables).
 
-	<li>
-	  Disable the configuration completely by adding the flag
-	  <code>-D DEAL_II_SETUP_DEFAULT_COMPILER_FLAGS=OFF</code>.
-	  Beware of the fact that certain features
-	  may still pull in necessary compiler flags.
-
         <li>
           You can setup additional debug compiler flags to provide test
           coverage information by adding the flag
diff --git a/doc/users/config.sample b/doc/users/config.sample
index 05dc55ecbf..e01d24f8d5 100644
--- a/doc/users/config.sample
+++ b/doc/users/config.sample
@@ -48,7 +48,6 @@
 # set(DEAL_II_DEFINITIONS_RELEASE "" CACHE STRING "")
 #
 # set(DEAL_II_ALLOW_PLATFORM_INTROSPECTION ON CACHE BOOL "")
-# set(DEAL_II_SETUP_DEFAULT_COMPILER_FLAGS ON CACHE BOOL "")
 # set(DEAL_II_SETUP_COVERAGE OFF CACHE BOOL "")
 # set(DEAL_II_UNITY_BUILD OFF CACHE BOOL "")
 # set(DEAL_II_EARLY_DEPRECATIONS OFF CACHE BOOL "")
-- 
2.39.5