Fix shared lib build with NAG Fortran on macOS#5824
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On Apple, the shared library link rule for Fortran used GCC-specific flags: -x f95-cpp-input (GCC preprocessing flag; NAG does not support it) -Wl,-shared (Linux linker flag; macOS needs -dynamiclib) The fix is NAG-specific — other non-GNU compilers (Intel, flang, Cray, etc.) are left alone since they may handle the existing code paths fine. Fix in two places (both already inside if(APPLE) / if(APPLE AND BUILD_STATIC_LIBS)): 1. Before add_library() (affects the main CMake Fortran shared lib rule): For NAG Fortran, substitute CMAKE_C_CREATE_SHARED_LIBRARY so the C compiler link rule is used instead. 2. Inside the APPLE AND BUILD_STATIC_LIBS block (the static->shared conversion trick for long argument lists): add an elseif(NAG) branch that uses the C compiler with -dynamiclib and auto-detects the NAG Fortran runtime (libf72rts) from the compiler's directory so that NAGf90_* symbols resolve. Tested with NAG 7.2.7243 on macOS/arm64.
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Fixes #5823
Note: This was done with Claude's help. I tried myself but it got to the point I needed some good insight on how CMake does shared library stuff.
On macOS, the shared library link rule for Fortran used two GCC-specific constructs that fail with the NAG Fortran compiler:
-x f95-cpp-input— a GCC preprocessing flag; NAG does not support it-Wl,-shared— a Linux linker flag; macOS requires-dynamiclibChanges in
CMakeLists.txt:Before
add_library()(must be set before targets are defined to take effect): for NAG Fortran on Apple, overrideCMAKE_Fortran_CREATE_SHARED_LIBRARYwith the C compiler link rule, which uses-dynamiclibcorrectly.Inside
if(APPLE AND BUILD_STATIC_LIBS)(the static→shared conversion trick for long argument lists): add anelseif(NAG)branch that uses the C compiler with-dynamiclib. The NAG Fortran runtime library (libf<XY>rts) is auto-detected via glob from the compiler's directory so thatNAGf90_*symbols resolve — this handles NAG 7.1 (libf71rts), 7.2 (libf72rts), future versions, etc. without hardcoding version numbers.Other non-GNU compilers (Intel, flang, Cray, etc.) are unaffected.
Tested with: NAG 7.2.7243 on macOS/arm64,
BUILD_SHARED_LIBS=ON BUILD_STATIC_LIBS=ON.