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Update compiler flags for consistency with MOM5 #27

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Update compiler flags for consistency with MOM5 #27

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14d5116
Update compiler flags for consistency with MOM5
dougiesquire Aug 21, 2026
057d085
Add back r8_flags
dougiesquire Aug 21, 2026
9e55c1c
Remove duplicate -r8; replace -i4 with -integer-size 32
dougiesquire Aug 21, 2026
c907a34
Remove duplicate and redundant -check noarg_temp_created
dougiesquire Aug 21, 2026
4a8501b
Address review comments
dougiesquire Aug 25, 2026
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57 changes: 30 additions & 27 deletions CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -33,9 +33,9 @@ include(GNUInstallDirs)
include(CheckFortranCompilerFlag)

if(NOT CMAKE_BUILD_TYPE MATCHES "^(Debug|Release|RelWithDebInfo|MinSizeRel)$")
message(STATUS "Setting build type to 'Release' as none was specified.")
message(STATUS "Setting build type to 'RelWithDebInfo' as none was specified.")
set(CMAKE_BUILD_TYPE
"Release"
"RelWithDebInfo"
CACHE STRING "Choose the type of build." FORCE)
set_property(CACHE CMAKE_BUILD_TYPE PROPERTY STRINGS "Debug" "Release" "MinSizeRel" "RelWithDebInfo")
endif()
Expand Down Expand Up @@ -63,37 +63,37 @@ if(CMAKE_Fortran_COMPILER_ID MATCHES "GNU")
set(r8_flags "-fdefault-real-8 -fdefault-double-8") # Fortran flags for 64BIT precision

# Copied from MOM5/bin/mkmf.template.nci.gfortran
set(CMAKE_Fortran_FLAGS "${CMAKE_Fortran_FLAGS} -fcray-pointer -fdefault-real-8 -ffree-line-length-none -fno-range-check -Waliasing -Wampersand -Warray-bounds -Wcharacter-truncation -Wconversion -Wline-truncation -Wintrinsics-std -Wsurprising -Wno-tabs -Wunderflow -Wunused-parameter -Wintrinsic-shadow -Wno-align-commons")
set(CMAKE_Fortran_FLAGS "${CMAKE_Fortran_FLAGS} -fcray-pointer -ffree-line-length-none -fno-range-check -Waliasing -Wampersand -Warray-bounds -Wcharacter-truncation -Wconversion -Wline-truncation -Wintrinsics-std -Wsurprising -Wno-tabs -Wunderflow -Wunused-parameter -Wintrinsic-shadow -Wno-align-commons")

@manodeep manodeep Aug 25, 2026

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Both Intel/IntelLLVM branches have an -i4 embedded into the "always-on" flags but GNU does not - is that intentional?

@manodeep manodeep Aug 25, 2026

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Also, do we need a big-endian-conversion flag?

@dougiesquire dougiesquire Aug 25, 2026

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Both Intel/IntelLLVM branches have an -i4 embedded into the "always-on" flags but GNU does not - is that intentional?

Yeah, as far as I know, there is no equivalent flag. 4-byte integers are gfortran's default. One can set -fdefault-integer-8, but there's no equivalent flag to "unset" it back to the default like there is for ifx/ifort.

@dougiesquire dougiesquire Aug 25, 2026

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Also, do we need a big-endian-conversion flag?

Yeah, probably a good idea. Added in 4a8501b

@manodeep manodeep Aug 31, 2026

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Sorry - totally forgot to update here. I trawled through the gfortran docs and yes, there is no equivalent compiler flag for -i4

# Note, -fallow-argument-mismatch is handled further down
check_fortran_compiler_flag("-fallow-invalid-boz" _boz_flag)
if(_boz_flag)
set(CMAKE_Fortran_FLAGS "${CMAKE_Fortran_FLAGS} -fallow-invalid-boz" )
endif()
set(CMAKE_Fortran_FLAGS_RELEASE "-O2")
set(CMAKE_Fortran_FLAGS_RELWITHDEBINFO "${CMAKE_Fortran_FLAGS_RELEASE} -g -frecord-gcc-switches -fbacktrace")
set(CMAKE_Fortran_FLAGS_DEBUG "-O0 -g -W -fbounds-check")

elseif(CMAKE_Fortran_COMPILER_ID STREQUAL "Intel")

# Precision-based Fortran compiler flags
set(r4_flags "-real-size 32") # Fortran flags for 32BIT precision
set(r8_flags "-real-size 64") # Fortran flags for 64BIT precision
set(r8_flags "${r8_flags} -no-prec-div -no-prec-sqrt")
set(r8_flags "-real-size 64 -no-prec-div -no-prec-sqrt") # Fortran flags for 64BIT precision

# Copied from MOM5/bin/mkmf.template.nci
set(CMAKE_Fortran_FLAGS "${CMAKE_Fortran_FLAGS} -fno-alias -safe-cray-ptr -fpe0 -ftz -assume byterecl -i4 -r8 -traceback -nowarn -check noarg_temp_created -assume nobuffered_io -convert big_endian -grecord-gcc-switches -fp-model precise -fp-model source -align all")
set(CMAKE_Fortran_FLAGS_RELEASE "-g3 -O2 -xCORE-AVX2 -debug all -check none")
set(CMAKE_Fortran_FLAGS_DEBUG "-g3 -O0 -debug all -check -check noarg_temp_created -check nopointer -warn -warn noerrors -ftrapuv")
set(CMAKE_Fortran_FLAGS "${CMAKE_Fortran_FLAGS} -fno-alias -safe-cray-ptr -fpe0 -ftz -assume byterecl -integer-size 32 -nowarn -assume nobuffered_io -convert big_endian -fp-model precise -fp-model source -align all")
set(CMAKE_Fortran_FLAGS_RELEASE "-O2 -xCORE-AVX2 -debug all -check none")
set(CMAKE_Fortran_FLAGS_RELWITHDEBINFO "${CMAKE_Fortran_FLAGS_RELEASE} -g3 -grecord-gcc-switches -traceback")
set(CMAKE_Fortran_FLAGS_DEBUG "-g3 -O0 -debug all -check -check noarg_temp_created -check nopointer -warn -warn noerrors -ftrapuv -traceback")

elseif(CMAKE_Fortran_COMPILER_ID STREQUAL "IntelLLVM")

# Precision-based Fortran compiler flags
set(r4_flags "-real-size 32") # Fortran flags for 32BIT precision
set(r8_flags "-real-size 64") # Fortran flags for 64BIT precision

# Copied from MOM5/bin/mkmf.template.nci
set(CMAKE_Fortran_FLAGS "${CMAKE_Fortran_FLAGS} -fno-alias -safe-cray-ptr -fpe0 -ftz -assume byterecl -i4 -r8 -traceback -nowarn -check noarg_temp_created -assume nobuffered_io -convert big_endian -grecord-gcc-switches -fp-model precise -fp-model source -align all")
set(CMAKE_Fortran_FLAGS_RELEASE "-g3 -O2 -xCORE-AVX2 -debug all -check none")
set(CMAKE_Fortran_FLAGS_DEBUG "-g3 -O0 -debug all -check -check noarg_temp_created -check nopointer -warn -warn noerrors -ftrapuv")
set(CMAKE_Fortran_FLAGS "${CMAKE_Fortran_FLAGS} -fno-alias -safe-cray-ptr -fpe0 -ftz -assume byterecl -integer-size 32 -nowarn -assume nobuffered_io -convert big_endian -fp-model precise -fp-model source -align all")
set(CMAKE_Fortran_FLAGS_RELEASE "-O2 -xCORE-AVX2 -debug all -check none")
set(CMAKE_Fortran_FLAGS_RELWITHDEBINFO "${CMAKE_Fortran_FLAGS_RELEASE} -g3 -grecord-gcc-switches -traceback")
set(CMAKE_Fortran_FLAGS_DEBUG "-g3 -O0 -debug all -check -check noarg_temp_created -check nopointer -warn -warn noerrors -ftrapuv -traceback")

else()
message(WARNING "Fortran compiler with ID ${CMAKE_Fortran_COMPILER_ID} will be used with CMake default options")
Expand All @@ -106,30 +106,34 @@ endif()
if(CMAKE_C_COMPILER_ID MATCHES "GNU")

# Copied from MOM5/bin/mkmf.template.nci.gfortran
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
set(CMAKE_C_FLAGS_DEBUG "-O0 -g")
set(CMAKE_C_FLAGS_RELEASE "-O2")
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
set(CMAKE_C_FLAGS_DEBUG "-O0 -g")
set(CMAKE_C_FLAGS_RELEASE "-O2")

@manodeep manodeep Aug 25, 2026

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I can't see any difference between these two changed lines? Are these whitespace-only changes?

@dougiesquire dougiesquire Aug 25, 2026

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Yeah, I added CMAKE_C_FLAGS_RELWITHDEBINFO (below) and tried to align things for readability/consistency (though I see I missed a space 😅)

@dougiesquire dougiesquire Aug 25, 2026

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Spacing is sorted in 4a8501b. If I don't adjust the whitespace for the existing sets they will be inconsistent with the new CMAKE_C_FLAGS_RELWITHDEBINFO set. But happy to do this if you prefer

@manodeep manodeep Aug 31, 2026

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I am fine with whichever works for you. Was just making sure that I wasn't missing anything :D

set(CMAKE_C_FLAGS_RELWITHDEBINFO "${CMAKE_C_FLAGS_RELEASE} -g")

elseif(CMAKE_C_COMPILER_ID STREQUAL "Intel")

# Copied from MOM5/bin/mkmf.template.nci
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fp-model precise -fp-model source")
set(CMAKE_C_FLAGS_DEBUG "-O0 -g -ftrapuv -traceback")
set(CMAKE_C_FLAGS_RELEASE "-O2 -debug minimal -xCORE-AVX2")
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fp-model precise -fp-model source")
set(CMAKE_C_FLAGS_DEBUG "-O0 -g -ftrapuv -traceback")
set(CMAKE_C_FLAGS_RELEASE "-O2 -debug minimal -xCORE-AVX2")
set(CMAKE_C_FLAGS_RELWITHDEBINFO "${CMAKE_C_FLAGS_RELEASE} -g")

elseif(CMAKE_C_COMPILER_ID STREQUAL "IntelLLVM")

# Copied from MOM5/bin/mkmf.template.nci
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fp-model precise")
set(CMAKE_C_FLAGS_DEBUG "-O0 -g -ftrapuv -traceback")
set(CMAKE_C_FLAGS_RELEASE "-O2 -debug minimal -xCORE-AVX2")
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fp-model precise")
set(CMAKE_C_FLAGS_DEBUG "-O0 -g -ftrapuv -traceback")
set(CMAKE_C_FLAGS_RELEASE "-O2 -debug minimal -xCORE-AVX2")
set(CMAKE_C_FLAGS_RELWITHDEBINFO "${CMAKE_C_FLAGS_RELEASE} -g")

elseif(CMAKE_C_COMPILER_ID MATCHES "Clang")

# Copied from MOM5/bin/mkmf.template.nci.gfortran
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
set(CMAKE_C_FLAGS_DEBUG "-O0 -g")
set(CMAKE_C_FLAGS_RELEASE "-O2")
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
set(CMAKE_C_FLAGS_DEBUG "-O0 -g")
set(CMAKE_C_FLAGS_RELEASE "-O2")
set(CMAKE_C_FLAGS_RELWITHDEBINFO "${CMAKE_C_FLAGS_RELEASE} -g")

else()
message(WARNING "C compiler with ID ${CMAKE_C_COMPILER_ID} will be used with CMake default options")
Expand All @@ -139,9 +143,8 @@ endif()

# Build options
option(OPENMP "Build FMS with OpenMP support" OFF)
# Commented out while CMAKE_Fortran_FLAGS contains -r8
# Only 64BIT (r8) builds are supported: only r8_flags (used below) is defined for the Fortran precision flags
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# option(32BIT "Build 32-bit (r4) FMS library" OFF)
# Refer to CMAKE_Fortran_FLAGS above, it contains -r8
option(64BIT "Build 64-bit (r8) FMS library" ON)
option(FPIC "Build with position independent code" OFF)
option(SHARED_LIBS "Build shared/dynamic libraries" OFF)
Expand Down
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