Simplify MSVC warning configuration

We've been setting /Wall on MSVC for a while, but /Wall in MSVC is
really "all". I.e., it's -Weverything in Clang and GCC, and includes
many warnings that are simply diagnostics. MSVC's own headers do not
promise to be clean under /Wall.

Rather, the equivalent of Clang and GCC's -Wall is /W4, which MSVC does
promise to pass. Under /Wall, every new MSVC release we've had to update
an ever-growing list of warning exceptions, to disable the
off-by-default warnings that were off for a reason. Switch to MSVC's
recommendations and just enable /W4.

From there, I've trimmed the exception list, now that we don't need to
re-disable disabled warnings. A few non-disabled warnings also no longer
need exceptions.

This should fix the build with VS2022, which was failing due to C5264.
C5264 flags a couple of instances in the library, but tons and tons in
MSVC headers and googletest. (The instances in the library are a little
goofy and reflect things that should have been 'inline constexpr', but
we can't rely on C++17 yet. Though I may go add a compat macro for
that.)

Fixed: 552
Change-Id: I9031c0d5bd4c7a4df1dc3040b38af9cfbcffc06e
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/56045
Auto-Submit: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: Adam Langley <agl@google.com>

1 files changed, 4 insertions, 53 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1ebba93..7e5a648 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -197,67 +197,22 @@ if(CMAKE_COMPILER_IS_GNUCXX OR CLANG)
   endif()
 elseif(MSVC)
   set(MSVC_DISABLED_WARNINGS_LIST
-      "C4061" # enumerator 'identifier' in switch of enum 'enumeration' is not
-              # explicitly handled by a case label
-              # Disable this because it flags even when there is a default.
       "C4100" # 'exarg' : unreferenced formal parameter
       "C4127" # conditional expression is constant
-      "C4200" # nonstandard extension used : zero-sized array in
-              # struct/union.
+      # C4204 and C4221 are C89-only restrictions which were dropped in C99, but
+      # VS2017 warns about it. They can be removed when we require VS2019.
       "C4204" # nonstandard extension used: non-constant aggregate initializer
       "C4221" # nonstandard extension used : 'identifier' : cannot be
               # initialized using address of automatic variable
-      "C4242" # 'function' : conversion from 'int' to 'uint8_t',
-              # possible loss of data
       "C4244" # 'function' : conversion from 'int' to 'uint8_t',
               # possible loss of data
       "C4267" # conversion from 'size_t' to 'int', possible loss of data
-      "C4371" # layout of class may have changed from a previous version of the
-              # compiler due to better packing of member '...'
-      "C4388" # signed/unsigned mismatch
-      "C4296" # '>=' : expression is always true
-      "C4350" # behavior change: 'std::_Wrap_alloc...'
-      "C4365" # '=' : conversion from 'size_t' to 'int',
-              # signed/unsigned mismatch
-      "C4389" # '!=' : signed/unsigned mismatch
-      "C4464" # relative include path contains '..'
-      "C4510" # 'argument' : default constructor could not be generated
-      "C4512" # 'argument' : assignment operator could not be generated
-      "C4514" # 'function': unreferenced inline function has been removed
-      "C4548" # expression before comma has no effect; expected expression with
-              # side-effect" caused by FD_* macros.
-      "C4610" # struct 'argument' can never be instantiated - user defined
-              # constructor required.
-      "C4623" # default constructor was implicitly defined as deleted
-      "C4625" # copy constructor could not be generated because a base class
-              # copy constructor is inaccessible or deleted
-      "C4626" # assignment operator could not be generated because a base class
-              # assignment operator is inaccessible or deleted
-      "C4628" # digraphs not supported with -Ze
-      "C4668" # 'symbol' is not defined as a preprocessor macro, replacing with
-              # '0' for 'directives'
-              # Disable this because GTest uses it everywhere.
       "C4706" # assignment within conditional expression
-      "C4710" # 'function': function not inlined
-      "C4711" # function 'function' selected for inline expansion
-      "C4800" # 'int' : forcing value to bool 'true' or 'false'
-              # (performance warning)
-      "C4820" # 'bytes' bytes padding added after construct 'member_name'
-      "C5026" # move constructor was implicitly defined as deleted
-      "C5027" # move assignment operator was implicitly defined as deleted
-      "C5045" # Compiler will insert Spectre mitigation for memory load if
-              # /Qspectre switch specified
-      )
-  set(MSVC_LEVEL4_WARNINGS_LIST
-      # See https://connect.microsoft.com/VisualStudio/feedback/details/1217660/warning-c4265-when-using-functional-header
-      "C4265" # class has virtual functions, but destructor is not virtual
       )
   string(REPLACE "C" " -wd" MSVC_DISABLED_WARNINGS_STR
                             ${MSVC_DISABLED_WARNINGS_LIST})
-  string(REPLACE "C" " -w4" MSVC_LEVEL4_WARNINGS_STR
-                            ${MSVC_LEVEL4_WARNINGS_LIST})
-  set(CMAKE_C_FLAGS   "-utf-8 -Wall -WX ${MSVC_DISABLED_WARNINGS_STR} ${MSVC_LEVEL4_WARNINGS_STR}")
-  set(CMAKE_CXX_FLAGS "-utf-8 -Wall -WX ${MSVC_DISABLED_WARNINGS_STR} ${MSVC_LEVEL4_WARNINGS_STR}")
+  set(CMAKE_C_FLAGS   "-utf-8 -W4 -WX ${MSVC_DISABLED_WARNINGS_STR}")
+  set(CMAKE_CXX_FLAGS "-utf-8 -W4 -WX ${MSVC_DISABLED_WARNINGS_STR}")
 endif()
 
 if(WIN32)
@@ -266,10 +221,6 @@ if(WIN32)
   add_definitions(-DNOMINMAX)
   # Allow use of fopen.
   add_definitions(-D_CRT_SECURE_NO_WARNINGS)
-  # VS 2017 and higher supports STL-only warning suppressions.
-  # A bug in CMake < 3.13.0 may cause the space in this value to
-  # cause issues when building with NASM. In that case, update CMake.
-  add_definitions("-D_STL_EXTRA_DISABLED_WARNINGS=4774 4987")
 endif()
 
 # pthread_rwlock_t on Linux requires a feature flag. We limit this to Linux