From b0da6712439fe44d84a158dceb5f946cc30ef68a Mon Sep 17 00:00:00 2001 From: Craig Scott Date: Thu, 18 Feb 2021 12:31:48 +1100 Subject: FetchContent: Don't update timestamps if files don't change The refactoring in 17e5516e60 (FetchContent: Invoke steps directly and avoid a separate sub-build, 2021-01-29) uses a different way of writing out the step scripts and updating time stamps when steps are executed. That inadvertently always wrote out the scripts for custom commands, even when the contents didn't change. This caused their timestamp to always be updated, resulting in those steps always being seen as out-of-date and needing to be re-executed. The way timestamps were checked to determine whether to re-execute a step also did not adequately account for file systems which only have second-resolution timestamps. The IS_NEWER_THAN if condition also returns true when timestamps are the same, so one needs to use the negative form to get a true "is newer than" test. ExternalProject is not susceptible to this problem because it uses file(GENERATE) to write out the script files and that only updates the file's timestamp if the contents change. It also mostly leaves timestamp checking to the build tool. --- Modules/ExternalProject.cmake | 26 ++++++++++++--- Tests/RunCMake/FetchContent/RunCMakeTest.cmake | 30 +++++++++++++++++ Tests/RunCMake/FetchContent/TimeStamps-stdout.txt | 2 ++ Tests/RunCMake/FetchContent/TimeStamps.cmake | 14 ++++++++ .../FetchContent/TimeStampsRerun-check.cmake | 38 ++++++++++++++++++++++ Tests/RunCMake/FetchContent/TimeStampsRerun.cmake | 1 + 6 files changed, 107 insertions(+), 4 deletions(-) create mode 100644 Tests/RunCMake/FetchContent/TimeStamps-stdout.txt create mode 100644 Tests/RunCMake/FetchContent/TimeStamps.cmake create mode 100644 Tests/RunCMake/FetchContent/TimeStampsRerun-check.cmake create mode 100644 Tests/RunCMake/FetchContent/TimeStampsRerun.cmake diff --git a/Modules/ExternalProject.cmake b/Modules/ExternalProject.cmake index 4a9809b..987b69a 100644 --- a/Modules/ExternalProject.cmake +++ b/Modules/ExternalProject.cmake @@ -2579,11 +2579,24 @@ function(_ep_write_command_script endif() if(genex_supported) - # Only written at generation phase + # Only written at generation phase. This will only change the file's + # timestamp if the contents change. file(GENERATE OUTPUT "${script_filename}" CONTENT "${script_content}") else() - # Written immediately, needed if script has to be invoked in configure phase - file(WRITE "${script_filename}" "${script_content}") + # Update the file immediately, needed if script has to be invoked in the + # configure phase (e.g. via FetchContent). We need to be careful to avoid + # updating the timestamp if the file contents don't change. The file(WRITE) + # command always updates the file, so avoid it if we don't need to call it. + set(doWrite TRUE) + if(EXISTS "${script_filename}") + file(READ "${script_filename}" existing_content) + if(existing_content STREQUAL script_content) + set(doWrite FALSE) + endif() + endif() + if(doWrite) + file(WRITE "${script_filename}" "${script_content}") + endif() endif() endfunction() @@ -3916,7 +3929,12 @@ function(_ep_do_preconfigure_steps_now name) if(NOT need_to_run) foreach(dep_file ${script_file} ${_EPdepends_${STEP}}) - if(NOT EXISTS ${dep_file} OR ${dep_file} IS_NEWER_THAN ${stamp_file}) + # IS_NEWER_THAN is also true if the timestamps are the same. On some + # file systems, we only have second resolution timestamps and the + # likelihood of having the same timestamp is high. Use the negative + # form to ensure we actually get a true "is newer than" test. + if(NOT EXISTS ${dep_file} OR + NOT ${stamp_file} IS_NEWER_THAN ${dep_file}) set(need_to_run TRUE) break() endif() diff --git a/Tests/RunCMake/FetchContent/RunCMakeTest.cmake b/Tests/RunCMake/FetchContent/RunCMakeTest.cmake index 13013fa..d7fd009 100644 --- a/Tests/RunCMake/FetchContent/RunCMakeTest.cmake +++ b/Tests/RunCMake/FetchContent/RunCMakeTest.cmake @@ -27,6 +27,36 @@ run_cmake_with_options(ManualSourceDirectoryRelative -D "FETCHCONTENT_SOURCE_DIR_WITHPROJECT:STRING=WithProject" ) +function(run_FetchContent_TimeStamps) + set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/TimeStamps) + file(REMOVE_RECURSE "${RunCMake_TEST_BINARY_DIR}") + file(MAKE_DIRECTORY "${RunCMake_TEST_BINARY_DIR}") + + # First run should execute the commands + run_cmake(TimeStamps) + + # Ensure that the file checks we use in the TimeStampsRerun-check.cmake script + # will not be defeated by file systems with only one second resolution. + # The IS_NEWER_THAN check returns TRUE if the timestamps of the two files are + # the same, which has been observed where filesystems only have one second + # resolution. + set(cmpTimeStamp ${RunCMake_TEST_BINARY_DIR}/cmpTimeStamp.txt) + set(checkTimeStamp ${RunCMake_TEST_BINARY_DIR}/cmpTimeStampCheck.txt) + file(TOUCH ${cmpTimeStamp}) + file(TOUCH ${checkTimeStamp}) + if("${cmpTimeStamp}" IS_NEWER_THAN "${checkTimeStamp}") + execute_process( + COMMAND ${CMAKE_COMMAND} -E sleep 1.125 + COMMAND_ERROR_IS_FATAL LAST + ) + endif() + + # Run again with no changes, no commands should re-execute + set(RunCMake_TEST_NO_CLEAN 1) + run_cmake(TimeStampsRerun) +endfunction() +run_FetchContent_TimeStamps() + function(run_FetchContent_DirOverrides) set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/DirOverrides-build) file(REMOVE_RECURSE "${RunCMake_TEST_BINARY_DIR}") diff --git a/Tests/RunCMake/FetchContent/TimeStamps-stdout.txt b/Tests/RunCMake/FetchContent/TimeStamps-stdout.txt new file mode 100644 index 0000000..2ba1ff4 --- /dev/null +++ b/Tests/RunCMake/FetchContent/TimeStamps-stdout.txt @@ -0,0 +1,2 @@ +.* *download executed +.* *patch executed diff --git a/Tests/RunCMake/FetchContent/TimeStamps.cmake b/Tests/RunCMake/FetchContent/TimeStamps.cmake new file mode 100644 index 0000000..33874f9 --- /dev/null +++ b/Tests/RunCMake/FetchContent/TimeStamps.cmake @@ -0,0 +1,14 @@ +include(FetchContent) + +# Do nothing for an update because it would result in always re-running the +# patch step. We want to test that a patch step that only depends on the +# download step is not re-run unnecessarily. +FetchContent_Declare(customCommands + PREFIX ${CMAKE_CURRENT_BINARY_DIR} + DOWNLOAD_COMMAND "${CMAKE_COMMAND}" -E echo "download executed" + UPDATE_COMMAND "" + PATCH_COMMAND "${CMAKE_COMMAND}" -E echo "patch executed" +) + +set(FETCHCONTENT_QUIET FALSE) +FetchContent_MakeAvailable(customCommands) diff --git a/Tests/RunCMake/FetchContent/TimeStampsRerun-check.cmake b/Tests/RunCMake/FetchContent/TimeStampsRerun-check.cmake new file mode 100644 index 0000000..c12a5f4 --- /dev/null +++ b/Tests/RunCMake/FetchContent/TimeStampsRerun-check.cmake @@ -0,0 +1,38 @@ +set(cmpFile ${RunCMake_TEST_BINARY_DIR}/cmpTimeStamp.txt) +set(scriptDir ${RunCMake_TEST_BINARY_DIR}/tmp) +set(stampDir ${RunCMake_TEST_BINARY_DIR}/src/customcommands-stamp) + +set(errorMessages) +if(NOT EXISTS "${cmpFile}") + list(APPEND errorMessages " ${cmpFile} is missing") +else() + foreach(script IN ITEMS mkdirs download patch) + set(scriptFile "${scriptDir}/customcommands-${script}.cmake") + if(NOT EXISTS "${scriptFile}") + list(APPEND errorMessages " ${scriptFile} is missing") + elseif(NOT "${cmpFile}" IS_NEWER_THAN "${scriptFile}") + list(APPEND errorMessages " ${scriptFile} was unexectedly updated") + endif() + endforeach() + + # special case, not a script, has different extension + set(repoInfoFile "${scriptDir}/customcommands-download-repoinfo.txt") + if(NOT EXISTS "${repoInfoFile}") + list(APPEND errorMessages " ${repoInfoFile} is missing") + elseif(NOT "${cmpFile}" IS_NEWER_THAN "${repoInfoFile}") + list(APPEND errorMessages " ${repoInfoFile} was unexectedly updated") + endif() + + foreach(step IN ITEMS download patch) + set(stampFile "${stampDir}/customcommands-${step}") + if(NOT EXISTS "${stampFile}") + list(APPEND errorMessages " ${stampFile} is missing") + elseif(NOT "${cmpFile}" IS_NEWER_THAN "${stampFile}") + list(APPEND errorMessages " ${stampFile} was unexectedly updated") + endif() + endforeach() +endif() + +if(errorMessages) + list(JOIN errorMessages "\n" RunCMake_TEST_FAILED) +endif() diff --git a/Tests/RunCMake/FetchContent/TimeStampsRerun.cmake b/Tests/RunCMake/FetchContent/TimeStampsRerun.cmake new file mode 100644 index 0000000..e13667a --- /dev/null +++ b/Tests/RunCMake/FetchContent/TimeStampsRerun.cmake @@ -0,0 +1 @@ +include(${CMAKE_CURRENT_LIST_DIR}/TimeStamps.cmake) -- cgit v0.12