Commit 1baf122c authored by Brad King's avatar Brad King

MSVC: Do not add /W3 to CMAKE_<LANG>_FLAGS by default

We do not add default warning flags on other compilers, and having
a warning flag in the default flags makes it hard for projects to
customize the warning level.  They need to use string processing
to remove `/W3` from `CMAKE_{C,CXX}_FLAGS`.  Therefore we should
drop it.

However, projects may be using string processing to replace `/W3`
with another flag, so we cannot simply drop it.  Add a policy to
drop it in a compatible way.

Fixes: #18317
parent 85421526
......@@ -57,6 +57,7 @@ Policies Introduced by CMake 3.15
.. toctree::
:maxdepth: 1
CMP0092: MSVC warning flags are not in CMAKE_{C,CXX}_FLAGS by default. </policy/CMP0092>
CMP0091: MSVC runtime library flags are selected by an abstraction. </policy/CMP0091>
CMP0090: export(PACKAGE) does not populate package registry by default. </policy/CMP0090>
CMP0089: Compiler id for IBM Clang-based XL compilers is now XLClang. </policy/CMP0089>
......
CMP0092
-------
MSVC warning flags are not in :variable:`CMAKE_<LANG>_FLAGS` by default.
When using MSVC-like compilers in CMake 3.14 and below, warning flags
like ``/W3`` are added to :variable:`CMAKE_<LANG>_FLAGS` by default.
This is problematic for projects that want to choose a different warning
level programmatically. In particular, it requires string editing of the
:variable:`CMAKE_<LANG>_FLAGS` variables with knowledge of the
CMake builtin defaults so they can be replaced.
CMake 3.15 and above prefer to leave out warning flags from the value of
:variable:`CMAKE_<LANG>_FLAGS` by default.
This policy provides compatibility with projects that have not been updated
to expect the lack of warning flags. The policy setting takes effect as of
the first :command:`project` or :command:`enable_language` command that
initializes :variable:`CMAKE_<LANG>_FLAGS` for a given lanuage ``<LANG>``.
.. note::
Once the policy has taken effect at the top of a project for a given
language, that choice must be used throughout the tree for that language.
In projects that have nested projects in subdirectories, be sure to
convert everything together.
The ``OLD`` behavior for this policy is to place MSVC warning flags in the
default :variable:`CMAKE_<LANG>_FLAGS` cache entries. The ``NEW`` behavior
for this policy is to *not* place MSVC warning flags in the default cache
entries.
This policy was introduced in CMake version 3.15. Use the
:command:`cmake_policy` command to set it to ``OLD`` or ``NEW`` explicitly.
Unlike many policies, CMake version |release| does *not* warn
when this policy is not set and simply uses ``OLD`` behavior.
.. include:: DEPRECATED.txt
msvc-warning-flags
------------------
* With MSVC-like compilers the value of :variable:`CMAKE_<LANG>_FLAGS`
no longer contains warning flags like ``/W3`` by default.
See policy :policy:`CMP0092`.
......@@ -13,7 +13,14 @@ else()
set(_DBGLIBS " /dbglibs")
set(_THREADS " /threads")
endif()
string(APPEND CMAKE_Fortran_FLAGS_INIT " /W1 /nologo /fpp${_LIBSDLL}${_THREADS}")
cmake_policy(GET CMP0092 _cmp0092)
if(NOT _cmp0092 STREQUAL "NEW")
string(APPEND CMAKE_Fortran_FLAGS_INIT " /W1")
endif()
unset(_cmp0092)
string(APPEND CMAKE_Fortran_FLAGS_INIT " /nologo /fpp${_LIBSDLL}${_THREADS}")
string(APPEND CMAKE_Fortran_FLAGS_DEBUG_INIT " /Od /debug:full${_DBGLIBS}")
string(APPEND CMAKE_Fortran_FLAGS_MINSIZEREL_INIT " /O1 /DNDEBUG")
string(APPEND CMAKE_Fortran_FLAGS_RELEASE_INIT " /O2 /DNDEBUG")
......
......@@ -366,21 +366,34 @@ macro(__windows_compiler_msvc lang)
set(_MDd " /MDd")
set(_MD " /MD")
endif()
cmake_policy(GET CMP0092 _cmp0092)
if(_cmp0092 STREQUAL "NEW")
set(_W3 "")
set(_Wall "")
else()
set(_W3 " /W3")
set(_Wall " -Wall")
endif()
unset(_cmp0092)
if(CMAKE_VS_PLATFORM_TOOLSET MATCHES "v[0-9]+_clang_.*")
# note: MSVC 14 2015 Update 1 sets -fno-ms-compatibility by default, but this does not allow one to compile many projects
# that include MS's own headers. CMake itself is affected project too.
string(APPEND CMAKE_${lang}_FLAGS_INIT " ${_PLATFORM_DEFINES}${_PLATFORM_DEFINES_${lang}} -fms-extensions -fms-compatibility -D_WINDOWS -Wall${_FLAGS_${lang}}")
string(APPEND CMAKE_${lang}_FLAGS_INIT " ${_PLATFORM_DEFINES}${_PLATFORM_DEFINES_${lang}} -fms-extensions -fms-compatibility -D_WINDOWS${_Wall}${_FLAGS_${lang}}")
string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT "${_MDd} -gline-tables-only -fno-inline -O0 ${_RTC1}")
string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT "${_MD} -O2 -DNDEBUG")
string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "${_MD} -gline-tables-only -O2 -fno-inline -DNDEBUG")
string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "${_MD} -DNDEBUG") # TODO: Add '-Os' once VS generator maps it properly for Clang
else()
string(APPEND CMAKE_${lang}_FLAGS_INIT " ${_PLATFORM_DEFINES}${_PLATFORM_DEFINES_${lang}} /D_WINDOWS /W3${_FLAGS_${lang}}")
string(APPEND CMAKE_${lang}_FLAGS_INIT " ${_PLATFORM_DEFINES}${_PLATFORM_DEFINES_${lang}} /D_WINDOWS${_W3}${_FLAGS_${lang}}")
string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT "${_MDd} /Zi /Ob0 /Od ${_RTC1}")
string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT "${_MD} /O2 /Ob2 /DNDEBUG")
string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "${_MD} /Zi /O2 /Ob1 /DNDEBUG")
string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "${_MD} /O1 /Ob1 /DNDEBUG")
endif()
unset(_Wall)
unset(_W3)
unset(_MDd)
unset(_MD)
......
......@@ -60,11 +60,20 @@ unset(__IMPLICT_DLINK_FLAGS)
string(REPLACE "/D" "-D" _PLATFORM_DEFINES_CUDA "${_PLATFORM_DEFINES}${_PLATFORM_DEFINES_CXX}")
string(APPEND CMAKE_CUDA_FLAGS_INIT " ${PLATFORM_DEFINES_CUDA} -D_WINDOWS -Xcompiler=\"/W3${_FLAGS_CXX}\"")
cmake_policy(GET CMP0092 _cmp0092)
if(_cmp0092 STREQUAL "NEW")
set(_W3 "")
else()
set(_W3 "/W3")
endif()
unset(_cmp0092)
string(APPEND CMAKE_CUDA_FLAGS_INIT " ${PLATFORM_DEFINES_CUDA} -D_WINDOWS -Xcompiler=\"${_W3}${_FLAGS_CXX}\"")
string(APPEND CMAKE_CUDA_FLAGS_DEBUG_INIT " -Xcompiler=\"-MDd -Zi -Ob0 -Od ${_RTC1}\"")
string(APPEND CMAKE_CUDA_FLAGS_RELEASE_INIT " -Xcompiler=\"-MD -O2 -Ob2\" -DNDEBUG")
string(APPEND CMAKE_CUDA_FLAGS_RELWITHDEBINFO_INIT " -Xcompiler=\"-MD -Zi -O2 -Ob1\" -DNDEBUG")
string(APPEND CMAKE_CUDA_FLAGS_MINSIZEREL_INIT " -Xcompiler=\"-MD -O1 -Ob1\" -DNDEBUG")
unset(_W3)
set(CMAKE_CUDA_STANDARD_LIBRARIES_INIT "${CMAKE_C_STANDARD_LIBRARIES_INIT}")
......
......@@ -270,7 +270,10 @@ class cmMakefile;
15, 0, cmPolicies::WARN) \
SELECT(POLICY, CMP0091, \
"MSVC runtime library flags are selected by an abstraction.", 3, 15, \
0, cmPolicies::WARN)
0, cmPolicies::WARN) \
SELECT(POLICY, CMP0092, \
"MSVC warning flags are not in CMAKE_<LANG>_FLAGS by default.", 3, \
15, 0, cmPolicies::WARN)
#define CM_SELECT_ID(F, A1, A2, A3, A4, A5, A6) F(A1)
#define CM_FOR_EACH_POLICY_ID(POLICY) \
......
......@@ -197,6 +197,7 @@ if(CMAKE_CXX_COMPILER_ID MATCHES "^(Cray|PGI|XL|XLClang)$")
endif()
if(MSVC)
add_RunCMake_test(MSVCRuntimeLibrary)
add_RunCMake_test(MSVCWarningFlags)
endif()
add_RunCMake_test(ObjectLibrary)
add_RunCMake_test(ParseImplicitIncludeInfo)
......
cmake_policy(SET CMP0092 NEW)
include(CMP0092-common.cmake)
cmake_policy(SET CMP0092 OLD)
include(CMP0092-common.cmake)
enable_language(C)
cmake_policy(GET CMP0092 cmp0092)
if(cmp0092 STREQUAL "NEW")
if("${CMAKE_C_FLAGS}" MATCHES "([/-]W[0-9])")
message(SEND_ERROR "CMAKE_C_FLAGS has '${CMAKE_MATCH_1}' under NEW behavior")
endif()
else()
if(NOT " ${CMAKE_C_FLAGS} " MATCHES " /W3 ")
message(SEND_ERROR "CMAKE_C_FLAGS does not have '/W3' under OLD behavior")
endif()
endif()
cmake_minimum_required(VERSION 3.14)
project(${RunCMake_TEST} NONE)
include(${RunCMake_TEST}.cmake)
include(RunCMake)
run_cmake(CMP0092-WARN)
run_cmake(CMP0092-OLD)
run_cmake(CMP0092-NEW)
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