[jira] [Commented] (THRIFT-6312) WITH_MT does not select the static runtime any more

["Jens Geyer (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/THRIFT-6312?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18117277#comment-18117277 ] 

Jens Geyer commented on THRIFT-6312:
------------------------------------

Withdrawn. {{WITH_MT}} being a no-op is not a bug to fix: it is load bearing by accident.

{{dd8ecde06}} moved the project away from a statically linked Windows compiler, and {{doc/ReleaseManagement.md}} has said since then that the released compiler "requires Visual C++ Runtime due to ASF regulations". Repairing {{WITH_MT}} would have turned the release build straight back into the statically linked one that commit removed.

What is actually stale is the other half of that cleanup: the document still asked the release manager to check for "only kernel32.dll", and {{build/docker/msvc/build-compiler.bat}} still passed {{-DWITH_MT=ON}}. That is THRIFT-6320, which replaces this issue.

_Drafted with AI assistance (Claude Opus 5); reviewed and posted by Jens Geyer._

> WITH_MT does not select the static runtime any more
> ---------------------------------------------------
>
>                 Key: THRIFT-6312
>                 URL: https://issues.apache.org/jira/browse/THRIFT-6312
>             Project: Thrift
>          Issue Type: Bug
>          Components: Build Process
>            Reporter: Jens Geyer
>            Priority: Major
>             Fix For: 0.26.0
>
>          Time Spent: 0.5h
>  Remaining Estimate: 0h
>
> h2. Symptom
> A compiler built with {{-DWITH_MT=ON}} - which is how {{build/docker/msvc/build-compiler.bat}} and the manual instructions in {{doc/ReleaseManagement.md}} build the Windows compiler that ships with a release - imports the shared C and C++ runtime:
> {noformat}
> KERNEL32.dll
> ole32.dll
> MSVCP140.dll
> VCRUNTIME140.dll
> VCRUNTIME140_1.dll
> api-ms-win-crt-heap-l1-1-0.dll
> api-ms-win-crt-runtime-l1-1-0.dll
> api-ms-win-crt-stdio-l1-1-0.dll
> api-ms-win-crt-time-l1-1-0.dll
> api-ms-win-crt-string-l1-1-0.dll
> api-ms-win-crt-filesystem-l1-1-0.dll
> api-ms-win-crt-locale-l1-1-0.dll
> api-ms-win-crt-math-l1-1-0.dll
> api-ms-win-crt-convert-l1-1-0.dll
> {noformat}
> {{doc/ReleaseManagement.md}} requires the released executable to depend on {{kernel32.dll}} only, so that it runs on a machine with no Visual C++ redistributable installed. The whole point of {{WITH_MT}} is to produce that.
> Observed on a {{windows-2025}} GitHub runner, CMake 3.31.6 with Visual Studio 2022. The container that builds the release compiler installs CMake 4.1.2.
> h2. Cause
> {{build/cmake/DefinePlatformSpecifc.cmake}} implements {{WITH_MT}} by rewriting the compiler flag variables:
> {code}
> foreach(CompilerFlag ${CompilerFlags})
>   string(REPLACE "/MD" "/MT" ${CompilerFlag} "${${CompilerFlag}}")
> endforeach()
> {code}
> Policy [CMP0091|https://cmake.org/cmake/help/latest/policy/CMP0091.html] took the MSVC runtime selection out of the per configuration compiler flag variables ({{CMAKE_CXX_FLAGS_RELEASE}} and its siblings, which is exactly the list the loop above walks) and moved it to the {{MSVC_RUNTIME_LIBRARY}} target property, which the {{CMAKE_MSVC_RUNTIME_LIBRARY}} variable initialises. That policy is NEW whenever a project requires CMake 3.15 or newer, and the top level {{CMakeLists.txt}} requires 3.16.
> So there is no {{/MD}} left in those variables, the replacement matches nothing, and {{WITH_MT}} does nothing at all. Neither {{CMP0091}} nor {{CMAKE_MSVC_RUNTIME_LIBRARY}} appears anywhere in the tree.
> It fails silently. The build succeeds, the configure summary still prints {{Using static runtime library: ON}}, and the libraries are still named {{thriftmt}} - the name promises a static runtime the binaries do not have.
> h2. Fix
> Set {{CMAKE_MSVC_RUNTIME_LIBRARY}} to {{MultiThreaded$<$<CONFIG:Debug>:Debug>}} when {{WITH_MT}} is on, before any target is created. The flag rewriting stays, because it is what still applies to a build that sets {{CMP0091}} to OLD.
> h2. Unrelated, but in the same list
> {{ole32.dll}} is expected and is not a redistributable: it is a Windows system DLL present on every Windows installation, pulled in by the {{CoCreateGuid}} call in {{compiler/cpp/src/thrift/generate/t_delphi_generator.cc}}. The "only depends on kernel32.dll" wording in {{doc/ReleaseManagement.md}} predates that call.
> _Drafted with AI assistance (Claude Opus 5); reviewed and posted by Jens Geyer._



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