[QUESTION] Are bounds checking and floating-point exceptions included in CMake build options?

[msulprizio]

I am trying to chase down what I think is an array-out-of-bounds error, so I've turned on the debug option in CMake. However, it isn't returning an information which led me to wonder if the debug option actually turns on checking bounds. I don't see any reference to bounds checking or floating point exceptions in the CMake files. We use both of those options regularly in debugging GEOS-Chem (that is the BOUNDS=y FPE=y switches in GNU Make) so we should also include them in CMake. In Makefile_Header.mk:

  # Turn on checking for floating-point exceptions                                        
  # These are approximately equivalent to -fpe0 -ftrapuv in IFORT                         
  # NOTE: GNU Fortran 4.4.7 does not allow for -finit-real-snan, so                       
  # we will only add this flag for versions newer than 4.4.7                              
  REGEXP             :=(^[Yy]|^[Yy][Ee][Ss])
  ifeq ($(shell [[ "$(FPE)" =~ $(REGEXP) ]] && echo true),true)
    FFLAGS           += -ffpe-trap=invalid,zero,overflow
    ifeq ($(NEWER_THAN_447),1)
      FFLAGS           += -finit-real=snan
    endif
  endif
  ifeq ($(shell [[ "$(FPEX)" =~ $(REGEXP) ]] && echo true),true)
    FFLAGS           += -ffpe-trap=invalid,zero,overflow
    ifeq ($(NEWER_THAN_447),1)
      FFLAGS           += -finit-real=snan
    endif
  endif
  # Add option for "array out of bounds" checking                                         
  REGEXP             := (^[Yy]|^[Yy][Ee][Ss])
  ifeq ($(shell [[ "$(BOUNDS)" =~ $(REGEXP) ]] && echo true),true)
    FFLAGS           += -fbounds-check
  endif

@LiamBindle can you confirm that (1) these options aren't already included in GEOS-Chem Classic's CMake options so far? and (2) advise on the best way to add this capability? If I understand correctly, I think we need to add to GC-DefaultCompilerOptions.cmake. Does it makes sense to include these in the debug option or as separate options?

[LiamBindle]

@msulprizio Yeah, you're correct, and GC-DefaultCompilerOptions.cmake is the right place to add these. I think it makes sense to add these--initially I omitted most of the debug flags with the idea that we'd add them on a need-to-use basis (to avoid carrying forward any old unsed flags). Feel free to update these to whatever you think is appropriate.

ifort's debug options for build type Debug are set here:

geos-chem/CMakeScripts/GC-DefaultCompilerOptions.cmake

Line 9 in e3b3b65

set(CMAKE_Fortran_FLAGS_DEBUG "-g -O0 -check arg_temp_created -debug all -DDEBUG")

and gfortran's options for build type Debug are set here:

geos-chem/CMakeScripts/GC-DefaultCompilerOptions.cmake

Line 18 in e3b3b65

set(CMAKE_Fortran_FLAGS_DEBUG "-g -gdwarf-2 -gstrict-dwarf -O0 -Wall -Wextra -Wconversion -Warray-temporaries -fcheck-array-temporaries")

[LiamBindle]

Oh, one more thing that I think might be relevent. Just so you know, you can set extra compiler options for your build directory by setting CMAKE_Fortran_FLAGS (see here). I think the flags that you're talking about should be added to the DEBUG flags, but I just wanted to mention this feature to increase awareness of it. This feature is useful for building GEOS-Chem with uncommon compiler options, like compiler options for using TAU or architecture-specific optimizations.

[msulprizio]

Thanks, @LiamBindle. This seems straightforward, so I will add bounds checking and FPE to the debug option in 12.8.1.

[lizziel]

Also heads up that file geos-chem/CMakeScripts/GC-DefaultCompilerOptions.cmake is deleted starting 13.0.0. Once this update goes into 12.8.1 we should also port it to dev/13.0.0.

[msulprizio]

This is now resolved in bc0c69f and will be included in 12.8.1.

The same fix has also been pushed to dev/13.0.0 in commit 2d0a7cb.