CMake: Rename and document the feature evaluation functions

Rename various functions and variables to hopefully make the behavior
of feature evaluation clearer.

The previous names like 'set_value' or 'set_cache_value' or 'cache'
were too generic and unclear. One would have to carefully read the
code to understand what was actually set.

Add some doc comments about what FEATURE_foo and QT_FEATURE_foo
represent.

Amends c4f5762b20dc20bab3cc62e9166d0e5b36e21cc6

Pick-to: 6.2
Task-number: QTBUG-94921
Change-Id: Ie6a7b83a4d54a83976b2706d4af82b39832d79f1
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>
This commit is contained in:
Alexandru Croitor 2021-07-08 17:21:12 +02:00
parent 51ae235080
commit cde126ef26

View File

@ -227,45 +227,54 @@ function(_qt_internal_dump_expression_values expression_dump expression)
set(${expression_dump} "${${expression_dump}}" PARENT_SCOPE)
endfunction()
function(qt_feature_set_cache_value resultVar feature condition calculated label)
# Stores the user provided value to FEATURE_${feature} if provided.
# If not provided, stores ${computed} instead.
# ${computed} is also stored when reconfiguring and the condition does not align with the user
# provided value.
#
function(qt_feature_check_and_save_user_provided_value resultVar feature condition computed label)
if (DEFINED "FEATURE_${feature}")
# Revisit value:
set(cache "${FEATURE_${feature}}")
# Revisit new user provided value
set(user_value "${FEATURE_${feature}}")
set(result "${user_value}")
# If the build is marked as dirty and the cache value doesn't meet the new condition,
# reset it to the calculated one.
# If the build is marked as dirty and the user_value doesn't meet the new condition,
# reset it to the computed one.
get_property(dirty_build GLOBAL PROPERTY _qt_dirty_build)
if(NOT condition AND cache AND dirty_build)
set(cache "${calculated}")
message(WARNING "Reset FEATURE_${feature} value to ${calculated}, because it doesn't \
if(NOT condition AND result AND dirty_build)
set(result "${computed}")
message(WARNING "Reset FEATURE_${feature} value to ${result}, because it doesn't \
meet its condition after reconfiguration.")
endif()
set(bool_values OFF NO FALSE N ON YES TRUE Y)
if ((cache IN_LIST bool_values) OR (cache GREATER_EQUAL 0))
set(result "${cache}")
if ((result IN_LIST bool_values) OR (result GREATER_EQUAL 0))
# All good!
else()
message(FATAL_ERROR "Sanity check failed: FEATURE_${feature} has invalid value \"${cache}\"!")
message(FATAL_ERROR
"Sanity check failed: FEATURE_${feature} has invalid value \"${result}\"!")
endif()
# Fix-up user-provided values
set("FEATURE_${feature}" "${cache}" CACHE BOOL "${label}" FORCE)
set("FEATURE_${feature}" "${result}" CACHE BOOL "${label}" FORCE)
else()
# Initial setup:
set("FEATURE_${feature}" "${calculated}" CACHE BOOL "${label}")
set(result "${calculated}")
set(result "${computed}")
set("FEATURE_${feature}" "${result}" CACHE BOOL "${label}")
endif()
set("${resultVar}" "${result}" PARENT_SCOPE)
endfunction()
macro(qt_feature_set_value feature cache condition label conditionExpression)
set(result "${cache}")
# Saves the final user value to QT_FEATURE_${feature}, after checking that the condition is met.
macro(qt_feature_check_and_save_internal_value
feature saved_user_value condition label conditionExpression)
set(result "${saved_user_value}")
if (NOT (condition) AND (cache))
if ((NOT condition) AND result)
_qt_internal_dump_expression_values(conditionDump "${conditionExpression}")
string(JOIN " " conditionString ${conditionExpression})
qt_configure_add_report_error("Feature \"${feature}\": Forcing to \"${cache}\" breaks its \
qt_configure_add_report_error("Feature \"${feature}\": Forcing to \"${result}\" breaks its \
condition:\n ${conditionString}\nCondition values dump:\n ${conditionDump}\n" RECORD_ON_FEATURE_EVALUATION)
endif()
@ -279,6 +288,30 @@ condition:\n ${conditionString}\nCondition values dump:\n ${conditionDump}
set(QT_KNOWN_FEATURES "${QT_KNOWN_FEATURES}" CACHE INTERNAL "" FORCE)
endmacro()
# The build system stores 2 CMake cache variables for each feature, to allow detecting value changes
# during subsequent reconfigurations.
#
#
# `FEATURE_foo` stores the user provided feature value for the current configuration run.
# It can be set directly by the user, or derived from INPUT_foo (also set by the user).
#
# If a value is not provided on initial configuration, the value will be auto-computed based on the
# various conditions of the feature.
# TODO: Document the various conditions and how they relate to each other.
#
#
# `QT_FEATURE_foo` stores the value of the feature from the previous configuration run.
# Its value is updated once with the newest user provided value after some checks are performed.
#
# This variable also serves as the main source of truth throughout the build system code to check
# if the feature is enabled, e.g. if(QT_FEATURE_foo)
#
# It is not meant to be set by the user. It is only modified by the build system.
#
# Comparing the values of QT_FEATURE_foo and FEATURE_foo, the build system can detect whether
# the user changed the value for a feature and thus recompute any dependent features.
#
function(qt_evaluate_feature feature)
# If the feature was already evaluated as dependency nothing to do here.
if(DEFINED "QT_FEATURE_${feature}")
@ -316,12 +349,12 @@ function(qt_evaluate_feature feature)
qt_evaluate_config_expression(enable_result ${arg_ENABLE})
qt_evaluate_config_expression(auto_detect ${arg_AUTODETECT})
if(${disable_result})
set(result OFF)
set(computed OFF)
elseif((${enable_result}) OR (${auto_detect}))
set(result ${condition})
set(computed ${condition})
else()
# feature not auto-detected and not explicitly enabled
set(result OFF)
set(computed OFF)
endif()
if("${arg_EMIT_IF}" STREQUAL "")
@ -347,13 +380,15 @@ function(qt_evaluate_feature feature)
"Feature ${feature} is insignificant in this configuration, "
"ignoring related command line option(s).")
qt_configure_add_report_entry(TYPE WARNING MESSAGE "${msg}")
set(result OFF)
set(computed OFF)
set(FEATURE_${feature} OFF)
endif()
qt_feature_set_cache_value(cache "${feature}" "${condition}" "${result}" "${arg_LABEL}")
qt_feature_set_value("${feature}" "${cache}" "${condition}" "${arg_LABEL}"
"${arg_CONDITION}")
qt_feature_check_and_save_user_provided_value(
saved_user_value "${feature}" "${condition}" "${computed}" "${arg_LABEL}")
qt_feature_check_and_save_internal_value(
"${feature}" "${saved_user_value}" "${condition}" "${arg_LABEL}" "${arg_CONDITION}")
# Store each feature's label for summary info.
set(QT_FEATURE_LABEL_${feature} "${arg_LABEL}" CACHE INTERNAL "")