[llvm] r186499 - Tweak the cmake interaction between CMAKE_BUILD_TYPE and LLVM_ENABLE_ASSERTIONS.

[Duncan Sands]

Hi Tilman,

On 20/09/13 19:56, Tilmann Scheller wrote:
> IMHO we should make an unspecified CMAKE_BUILD_TYPE just default to
> Debug+Asserts (this would also increase consistency with the Makefile build).

I googled a bit for how to give CMAKE_BUILD_TYPE a default value, but it seemed
surprisingly tricky, too tricky for a cmake noob like myself.  But maybe someone
who actually knows something about cmake could give it a go?

Ciao, Duncan.

>
> I ran into a similar issue yesterday, I was wondering why an assert wouldn’t
> trigger. Looking at the disassembly I realized that the code for the assert was
> actually not there even though I was building with CMAKE_BUILD_TYPE=Debug. How
> could that happen?
>
> Turns out when I did the initial configure of my build directory I forgot to set
> CMAKE_BUILD_TYPE, so once I realized I couldn’t debug my binary I did a
> CMAKE_BUILD_TYPE=Debug. After that debugging works fine again, however asserts
> are still turned off!
>
> Regards,
>
> Tilmann
>
> On Sep 20, 2013, at 4:49 AM, Richard Smith <richard at metafoo.co.uk
> <mailto:richard at metafoo.co.uk>> wrote:
>
>> On Wed, Jul 17, 2013 at 2:34 AM, Duncan Sands<baldrick at free.fr
>> <mailto:baldrick at free.fr>>wrote:
>>
>>     Author: baldrick
>>     Date: Wed Jul 17 04:34:51 2013
>>     New Revision: 186499
>>
>>     URL:http://llvm.org/viewvc/llvm-project?rev=186499&view=rev
>>     Log:
>>     Tweak the cmake interaction between CMAKE_BUILD_TYPE and
>>     LLVM_ENABLE_ASSERTIONS.
>>     The issue is that CMAKE_BUILD_TYPE=RelWithDebInfo
>>     LLVM_ENABLE_ASSERTIONS=ON was
>>     not building with assertions enabled.  (I was unable to find what in the LLVM
>>     source tree was adding -DNDEBUG to the build line in this case, so decided
>>     that
>>     it must be cmake itself that was adding it - this may depend on the cmake
>>     version).  The fix treats any mode that is not Debug as being the same as
>>     Release for this purpose (previously it was being assumed that cmake would
>>     only
>>     add -DNDEBUG for Release and not for RelWithDebInfo or MinSizeRel).  If other
>>     versions of cmake don't add -DNDEBUG for RelWithDebInfo then that's OK: with
>>     this change you just get a useless but harmless -UNDEBUG or -DNDEBUG.
>>
>>
>> I believe this change broke my build setup. Previously a default cmake setup
>> (with no CMAKE_BUILD_TYPE set) would build with no debug, no optimization, and
>> assertions enabled (a pretty good default setup for development). Now we get
>> no assertions in that setup. Was that deliberate?
>>
>>     Modified:
>>     llvm/trunk/CMakeLists.txt
>>     llvm/trunk/cmake/modules/HandleLLVMOptions.cmake
>>
>>     Modified: llvm/trunk/CMakeLists.txt
>>     URL:http://llvm.org/viewvc/llvm-project/llvm/trunk/CMakeLists.txt?rev=186499&r1=186498&r2=186499&view=diff
>>     ==============================================================================
>>     --- llvm/trunk/CMakeLists.txt (original)
>>     +++ llvm/trunk/CMakeLists.txt Wed Jul 17 04:34:51 2013
>>     @@ -153,7 +153,7 @@ endif()
>>      option(LLVM_ENABLE_PEDANTIC "Compile with pedantic enabled." ON)
>>      option(LLVM_ENABLE_WERROR "Fail and stop if a warning is triggered." OFF)
>>
>>     -if( uppercase_CMAKE_BUILD_TYPE STREQUAL "RELEASE" )
>>     +if( NOT uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG" )
>>        option(LLVM_ENABLE_ASSERTIONS "Enable assertions" OFF)
>>      else()
>>        option(LLVM_ENABLE_ASSERTIONS "Enable assertions" ON)
>>
>>     Modified: llvm/trunk/cmake/modules/HandleLLVMOptions.cmake
>>     URL:http://llvm.org/viewvc/llvm-project/llvm/trunk/cmake/modules/HandleLLVMOptions.cmake?rev=186499&r1=186498&r2=186499&view=diff
>>     ==============================================================================
>>     --- llvm/trunk/cmake/modules/HandleLLVMOptions.cmake (original)
>>     +++ llvm/trunk/cmake/modules/HandleLLVMOptions.cmake Wed Jul 17 04:34:51 2013
>>     @@ -17,9 +17,9 @@ if( LLVM_ENABLE_ASSERTIONS )
>>        if( NOT MSVC )
>>          add_definitions( -D_DEBUG )
>>        endif()
>>     -  # On Release builds cmake automatically defines NDEBUG, so we
>>     +  # On non-Debug builds cmake automatically defines NDEBUG, so we
>>        # explicitly undefine it:
>>     -  if( uppercase_CMAKE_BUILD_TYPE STREQUAL "RELEASE" )
>>     +  if( NOT uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG" )
>>          add_definitions( -UNDEBUG )
>>          # Also remove /D NDEBUG to avoid MSVC warnings about conflicting defines.
>>          string (REGEX REPLACE "(^| )[/-]D *NDEBUG($| )" " "
>>
>>
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