diff options
author | Craig Scott <craig.scott@qt.io> | 2021-03-16 12:27:53 +1100 |
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committer | Craig Scott <craig.scott@qt.io> | 2021-03-18 15:06:14 +1100 |
commit | 63a0d263cf233ddf85a60678829298b50e8d1f26 (patch) | |
tree | 5abdfee0f1ba50c6097ca18a97e44a4c01c7d4d5 /cmake/QtPlugins.cmake.in | |
parent | 2409e9b2c7ca433ac1183efb763fdb99edf59235 (diff) |
Prevent static plugin triggering autogen dependency on reconfigure
A call to file(WRITE) will unconditionally update the file's timestamp
even if the file's contents don't change. The *Plugin.cpp file was
being written using configure_file() which avoids that, but the .cpp.in
file it was configuring from was being written out using file(WRITE)
every time CMake ran. Autogen saw that file as a dependency and then
regenerated the mocs_compilation.cpp file, which in turn results in
unnecessary rebuilds and relinking when nothing is actually changing.
The file(WRITE) - configure_file() dance is no longer needed anyway,
since the generated *Plugin.cpp file is very simple with no
substitutions required. Therefore, we can simplify that file's
generation with a single file(WRITE) that only executes if the file
contents will change or the file is missing.
Pick-to: 6.1 6.0
Change-Id: I2b7d1ff678b85ea7811969d656555592c9b6865f
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>
Diffstat (limited to 'cmake/QtPlugins.cmake.in')
-rw-r--r-- | cmake/QtPlugins.cmake.in | 22 |
1 files changed, 15 insertions, 7 deletions
diff --git a/cmake/QtPlugins.cmake.in b/cmake/QtPlugins.cmake.in index 6df9541e18..37ab1bb107 100644 --- a/cmake/QtPlugins.cmake.in +++ b/cmake/QtPlugins.cmake.in @@ -139,15 +139,23 @@ function(__qt_internal_add_static_plugins_once) set(_generated_qt_plugin_file_name "${CMAKE_CURRENT_BINARY_DIR}/qt_@QT_MODULE@_${target}.cpp") - set(_generated_qt_plugin_file_name_template "${_generated_qt_plugin_file_name}.in") set(_generated_qt_plugin_file_content "#include <QtPlugin>\nQ_IMPORT_PLUGIN(${_classname})") - # Generate a source file to import that plug-in. Has to be done with configure_file, - # because file(GENERATE) and target_sources has issues with scopes. - file(WRITE "${_generated_qt_plugin_file_name_template}" - "${_generated_qt_plugin_file_content}") - configure_file("${_generated_qt_plugin_file_name_template}" - "${_generated_qt_plugin_file_name}") + # Generate a source file to import that plug-in. Be careful not to + # update the timestamp of the generated file if we are not going to + # change anything. Otherwise we will trigger CMake's autogen to re-run + # and executables will then need to at least relink. + set(need_write TRUE) + if(EXISTS ${_generated_qt_plugin_file_name}) + file(READ ${_generated_qt_plugin_file_name} old_contents) + if(old_contents STREQUAL "${_generated_qt_plugin_file_content}") + set(need_write FALSE) + endif() + endif() + if(need_write) + file(WRITE "${_generated_qt_plugin_file_name}" + "${_generated_qt_plugin_file_content}") + endif() target_sources(${_module_target} INTERFACE "$<${_plugin_condition}:${_generated_qt_plugin_file_name}>") |