cmake: Disable the new (CMake 3.16) PCH support

Subprojects that use the CMake PCH feature will cause
compilation/linker errors. The CMake PCH support
should thus be disabled until this can be properly
translated to meson.

mesonbuild/cmake/data/preload.cmake

@@ -11,6 +11,11 @@ endmacro()
 macro(meson_ps_reload_vars)
 endmacro()
 
+macro(meson_ps_disabled_function)
+  message(WARNING "The function '${ARGV0}' is disabled in the context of CMake subporjects.\n"
+                  "This should not be an issue but may lead to compilaton errors.")
+endmacro()
+
 # Helper macro to inspect the current CMake state
 macro(meson_ps_inspect_vars)
   set(MESON_PS_CMAKE_CURRENT_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}")
@@ -63,5 +68,10 @@ function(set_source_files_properties)
   endwhile()
 endfunction()
 
+# Disable some functions that would mess up the CMake meson integration
+macro(target_precompile_headers)
+  meson_ps_disabled_function(target_precompile_headers)
+endmacro()
+
 set(MESON_PS_DELAYED_CALLS add_custom_command;add_custom_target;set_property)
 meson_ps_reload_vars()

mesonbuild/cmake/traceparser.py

@@ -123,6 +123,7 @@ class CMakeTraceParser:
             # meaning here in the trace parser.
             'meson_ps_execute_delayed_calls': self._meson_ps_execute_delayed_calls,
             'meson_ps_reload_vars': self._meson_ps_reload_vars,
+            'meson_ps_disabled_function': self._meson_ps_disabled_function,
         }  # type: T.Dict[str, T.Callable[[CMakeTraceLine], None]]
 
     def trace_args(self) -> T.List[str]:
@@ -618,6 +619,13 @@ class CMakeTraceParser:
     def _meson_ps_reload_vars(self, tline: CMakeTraceLine) -> None:
         self.delayed_commands = self.get_cmake_var('MESON_PS_DELAYED_CALLS')
 
+    def _meson_ps_disabled_function(self, tline: CMakeTraceLine) -> None:
+        args = list(tline.args)
+        if not args:
+            mlog.error('Invalid preload.cmake script! At least one argument to `meson_ps_disabled_function` is expected')
+            return
+        mlog.warning('The CMake function "{}" was disabed to avoid compatibility issues with Meson.'.format(args[0]))
+
     def _lex_trace_human(self, trace: str) -> T.Generator[CMakeTraceLine, None, None]:
         # The trace format is: '<file>(<line>):  <func>(<args -- can contain \n> )\n'
         reg_tline = re.compile(r'\s*(.*\.(cmake|txt))\(([0-9]+)\):\s*(\w+)\(([\s\S]*?) ?\)\s*\n', re.MULTILINE)

mesonbuild/mesondata.py

@@ -19,6 +19,7 @@
 ####
 
 
+# TODO: Remember to remove this also from tools/gen_data.py
 from ._pathlib import Path
 import typing as T
 
@@ -272,6 +273,11 @@ endmacro()
 macro(meson_ps_reload_vars)
 endmacro()
 
+macro(meson_ps_disabled_function)
+  message(WARNING "The function '${ARGV0}' is disabled in the context of CMake subporjects.\n"
+                  "This should not be an issue but may lead to compilaton errors.")
+endmacro()
+
 # Helper macro to inspect the current CMake state
 macro(meson_ps_inspect_vars)
   set(MESON_PS_CMAKE_CURRENT_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}")
@@ -324,6 +330,11 @@ function(set_source_files_properties)
   endwhile()
 endfunction()
 
+# Disable some functions that would mess up the CMake meson integration
+macro(target_precompile_headers)
+  meson_ps_disabled_function(target_precompile_headers)
+endmacro()
+
 set(MESON_PS_DELAYED_CALLS add_custom_command;add_custom_target;set_property)
 meson_ps_reload_vars()
 '''
@@ -368,7 +379,7 @@ mesondata = {
     ),
     'cmake/data/preload.cmake': DataFile(
         Path('cmake/data/preload.cmake'),
-        '064d047b18a5c919ad016b838bed50c5d40aebe9e53da0e70eff9d52a2c1ca1f',
+        'bbc441ededf2c7da2d0e640038ccbf4e818b73a2ba75084e1b4dbf05d8bca865',
         file_3_data_preload_cmake,
     ),
 }

test cases/cmake/1 basic/subprojects/cmMod/CMakeLists.txt

@@ -10,5 +10,11 @@ add_definitions("-DDO_NOTHING_JUST_A_FLAG=1")
 add_library(cmModLib++ SHARED cmMod.cpp)
 target_compile_definitions(cmModLib++ PRIVATE MESON_MAGIC_FLAG=21)
 target_compile_definitions(cmModLib++ INTERFACE MESON_MAGIC_FLAG=42)
+
+# Test PCH support
+if(${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.16.0")
+  target_precompile_headers(cmModLib++ PRIVATE "cpp_pch.hpp")
+endif()
+
 include(GenerateExportHeader)
 generate_export_header(cmModLib++)

test cases/cmake/1 basic/subprojects/cmMod/cpp_pch.hpp

@@ -0,0 +1,2 @@
+#include <vector>
+#include <string>

tools/gen_data.py

@@ -78,7 +78,8 @@ def main() -> int:
         ####
 
 
-        from pathlib import Path
+        # TODO: Remember to remove this also from tools/gen_data.py
+        from ._pathlib import Path
         import typing as T
 
         if T.TYPE_CHECKING: