Jens Geyer created THRIFT-6312:
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Summary: 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
Fix For: 0.26.0
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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