[lldb][CMake] Add LLDB_ENABLE_WERROR option

[sgraenitz]

Summary

Treat warnings as errors all over LLDB when enabled. Defaults to OFF.

[sgraenitz]

lldb/cmake/modules/LLDBConfig.cmake

318

I copied the flag from LLVM. Is it the right one for MSVC?

[labath]

So, why doesn't LLVM_ENABLE_WERROR suffice? It looks like that ought to work even in standalone builds...

[sgraenitz]

In D65939#1620780, @labath wrote:

So, why doesn't LLVM_ENABLE_WERROR suffice? It looks like that ought to work even in standalone builds...

LLVM_ENABLE_WERROR affects the entire build tree. If another subproject causes a warning the build fails. In a way, you are right that this is sufficient, because the no-warnings policy seems to work well upstream.
The issue I was trying to solve is, that we can't use the setting with some external subprojects, because they are not strictly warning free. But then it may be better to have downstream. I agree.

[stella.stamenova]

lldb/cmake/modules/LLDBConfig.cmake

318

Yes:
https://docs.microsoft.com/en-us/cpp/build/reference/compiler-option-warning-level?view=vs-2019
https://docs.microsoft.com/en-us/cpp/build/reference/wx-treat-linker-warnings-as-errors?view=vs-2019

lldb/cmake/caches/Apple-lldb-macOS.cmake

 include(${CMAKE_CURRENT_LIST_DIR}/Apple-lldb-base.cmake)
 
 set(LLDB_BUILD_FRAMEWORK ON CACHE BOOL "")
 set(LLDB_NO_INSTALL_DEFAULT_RPATH ON CACHE BOOL "")
+set(LLDB_ENABLE_WERROR ON CACHE BOOL "")
 set(CMAKE_OSX_DEPLOYMENT_TARGET 10.11 CACHE STRING "")
 
 # Default install location on the enduser machine. On the build machine, use the
 # DESTDIR environment variable in order to relocate the whole installation, e.g.:
 # `DESTDIR=/tmp ninja install-distribution`
 set(CMAKE_INSTALL_PREFIX /Applications/Xcode.app/Contents/Developer/usr CACHE STRING "")
 
 # Install location for LLDB.framework on the enduser machine.

lldb/cmake/modules/LLDBConfig.cmake

 option(LLDB_DISABLE_CURSES "Disable Curses integration." ${default_disable_curses})
 option(LLDB_DISABLE_LIBEDIT "Disable the use of editline." ${default_disable_libedit})
 option(LLDB_RELOCATABLE_PYTHON "Use the PYTHONHOME environment variable to locate Python." OFF)
 option(LLDB_USE_SYSTEM_SIX "Use six.py shipped with system and do not install a copy of it" OFF)
 option(LLDB_USE_ENTITLEMENTS "When codesigning, use entitlements if available" ON)
 option(LLDB_BUILD_FRAMEWORK "Build LLDB.framework (Darwin only)" OFF)
 option(LLDB_NO_INSTALL_DEFAULT_RPATH "Disable default RPATH settings in binaries" OFF)
 option(LLDB_USE_SYSTEM_DEBUGSERVER "Use the system's debugserver for testing (Darwin only)." OFF)
+option(LLDB_ENABLE_WERROR "Fail and stop if a warning is triggered." ${LLVM_ENABLE_WERROR})
 
 if(LLDB_BUILD_FRAMEWORK)
   if(NOT APPLE)
     message(FATAL_ERROR "LLDB.framework can only be generated when targeting Apple platforms")
   endif()
   # CMake 3.6 did not correctly emit POST_BUILD commands for Apple Framework targets
   # CMake < 3.8 did not have the BUILD_RPATH target property
   if(CMAKE_VERSION VERSION_LESS 3.8)
add_definitions(
     -wd4150 # Suppress 'warning C4150: deletion of pointer to incomplete type'
     -wd4201 # Suppress 'warning C4201: nonstandard extension used: nameless struct/union'
     -wd4251 # Suppress 'warning C4251: T must have dll-interface to be used by clients of class U.'
     -wd4521 # Suppress 'warning C4521: 'type' : multiple copy constructors specified'
     -wd4530 # Suppress 'warning C4530: C++ exception handler used, but unwind semantics are not enabled.'
   )
 endif()
 
+if(LLDB_ENABLE_WERROR)
+  set(flag_werror "-Werror")
+  if(MSVC)
+    set(flag_werror "/WX")
+  endif()
+
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${flag_werror}")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${flag_werror}")
+endif()
+
 # Use the Unicode (UTF-16) APIs by default on Win32
 if (CMAKE_SYSTEM_NAME MATCHES "Windows")
     add_definitions( -D_UNICODE -DUNICODE )
 endif()
 
 # If LLDB_VERSION_* is specified, use it, if not use LLVM_VERSION_*.
 if(NOT DEFINED LLDB_VERSION_MAJOR)
   set(LLDB_VERSION_MAJOR ${LLVM_VERSION_MAJOR})