Add flags to link main programs with C/C++ main (#896)

perazz · web-flow · commit 39a97c41cc9b · 2023-05-09T12:30:56.000-05:00
diff --git a/src/fpm_compiler.F90 b/src/fpm_compiler.F90
@@ -96,6 +96,8 @@ module fpm_compiler
     procedure :: get_include_flag
     !> Get feature flag
     procedure :: get_feature_flag
+    !> Get flags for the main linking command
+    procedure :: get_main_flags
     !> Compile a Fortran object
     procedure :: compile_fortran
     !> Compile a C object
@@ -106,6 +108,8 @@ module fpm_compiler
     procedure :: link
     !> Check whether compiler is recognized
     procedure :: is_unknown
+    !> Check whether compiler is Intel family
+    procedure :: is_intel
     !> Enumerate libraries, based on compiler and platform
     procedure :: enumerate_libraries
 end type compiler_t
@@ -211,7 +215,7 @@ module fpm_compiler
     flag_cray_implicit_typing = " -el", &
     flag_cray_fixed_form = " -ffixed", &
     flag_cray_free_form = " -ffree"
-    
+
 contains
 
 
@@ -440,7 +444,7 @@ pure subroutine set_cpp_preprocessor_flags(id, flags)
 
 end subroutine set_cpp_preprocessor_flags
 
-!> This function will parse and read the macros list and 
+!> This function will parse and read the macros list and
 !> return them as defined flags.
 function get_macros(id, macros_list, version) result(macros)
     integer(compiler_enum), intent(in) :: id
@@ -450,7 +454,7 @@ function get_macros(id, macros_list, version) result(macros)
     character(len=:), allocatable :: macros
     character(len=:), allocatable :: macro_definition_symbol
     character(:), allocatable :: valued_macros(:)
-    
+
 
     integer :: i
 
@@ -473,10 +477,10 @@ function get_macros(id, macros_list, version) result(macros)
     end if
 
     do i = 1, size(macros_list)
-        
+
         !> Split the macro name and value.
         call split(macros_list(i)%s, valued_macros, delimiters="=")
- 
+
         if (size(valued_macros) > 1) then
             !> Check if the value of macro starts with '{' character.
             if (str_begins_with_str(trim(valued_macros(size(valued_macros))), "{")) then
@@ -486,15 +490,15 @@ function get_macros(id, macros_list, version) result(macros)
 
                     !> Check if the string contains "version" as substring.
                     if (index(valued_macros(size(valued_macros)), "version") /= 0) then
-                    
+
                         !> These conditions are placed in order to ensure proper spacing between the macros.
                         macros = macros//macro_definition_symbol//trim(valued_macros(1))//'='//version
                         cycle
                     end if
                 end if
-            end if 
+            end if
         end if
-         
+
         macros = macros//macro_definition_symbol//macros_list(i)%s
 
     end do
@@ -664,6 +668,49 @@ function get_feature_flag(self, feature) result(flags)
 end function get_feature_flag
 
 
+!> Get special flags for the main linker
+subroutine get_main_flags(self, language, flags)
+    class(compiler_t), intent(in) :: self
+    character(len=*), intent(in) :: language
+    character(len=:), allocatable, intent(out) :: flags
+
+    flags = ""
+    select case(language)
+
+    case("fortran")
+        flags = ""
+
+    case("c")
+
+        ! If the main program is on a C/C++ source, the Intel Fortran compiler requires option
+        ! -nofor-main to avoid "duplicate main" errors.
+        ! https://stackoverflow.com/questions/36221612/p3dfft-compilation-ifort-compiler-error-multiple-definiton-of-main
+        select case(self%id)
+           case(id_intel_classic_nix, id_intel_classic_mac, id_intel_llvm_nix)
+               flags = '-nofor-main'
+           case(id_intel_classic_windows,id_intel_llvm_windows)
+               flags = '/nofor-main'
+           case (id_pgi,id_nvhpc)
+               flags = '-Mnomain'
+        end select
+
+    case("c++","cpp","cxx")
+
+        select case(self%id)
+           case(id_intel_classic_nix, id_intel_classic_mac, id_intel_llvm_nix)
+               flags = '-nofor-main'
+           case(id_intel_classic_windows,id_intel_llvm_windows)
+               flags = '/nofor-main'
+           case (id_pgi,id_nvhpc)
+               flags = '-Mnomain'
+        end select
+
+    case default
+        error stop "Unknown language '"//language//'", try "fortran", "c", "c++"'
+    end select
+
+end subroutine get_main_flags
+
 subroutine get_default_c_compiler(f_compiler, c_compiler)
     character(len=*), intent(in) :: f_compiler
     character(len=:), allocatable, intent(out) :: c_compiler
@@ -883,6 +930,12 @@ pure function is_unknown(self)
     is_unknown = self%id == id_unknown
 end function is_unknown
 
+pure logical function is_intel(self)
+    class(compiler_t), intent(in) :: self
+    is_intel = any(self%id == [id_intel_classic_mac,id_intel_classic_nix,id_intel_classic_windows,&
+                               id_intel_llvm_nix,id_intel_llvm_unknown,id_intel_llvm_windows])
+end function is_intel
+
 !>
 !> Enumerate libraries, based on compiler and platform
 !>
@@ -917,7 +970,7 @@ subroutine new_compiler(self, fc, cc, cxx, echo, verbose)
     logical, intent(in) :: verbose
 
     self%id = get_compiler_id(fc)
-    
+
     self%echo = echo
     self%verbose = verbose
     self%fc = fc
diff --git a/src/fpm_targets.f90 b/src/fpm_targets.f90
@@ -194,7 +194,7 @@ subroutine build_target_list(targets,model)
     type(fpm_model_t), intent(inout), target :: model
 
     integer :: i, j, n_source, exe_type
-    character(:), allocatable :: xsuffix, exe_dir
+    character(:), allocatable :: xsuffix, exe_dir, compile_flags
     logical :: with_lib
 
     ! Check for empty build (e.g. header-only lib)
@@ -240,14 +240,14 @@ subroutine build_target_list(targets,model)
                                 features = model%packages(j)%features, &
                                 macros = model%packages(j)%macros, &
                                 version = model%packages(j)%version)
-                                
+
 
                     if (with_lib .and. sources(i)%unit_scope == FPM_SCOPE_LIB) then
                         ! Archive depends on object
                         call add_dependency(targets(1)%ptr, targets(size(targets))%ptr)
                     end if
 
-                case (FPM_UNIT_CPPSOURCE) 
+                case (FPM_UNIT_CPPSOURCE)
 
                     call add_target(targets,package=model%packages(j)%name,source = sources(i), &
                                 type = FPM_TARGET_CPP_OBJECT, &
@@ -307,14 +307,29 @@ subroutine build_target_list(targets,model)
                                     output_name = join_path(exe_dir, &
                                     sources(i)%exe_name//xsuffix))
 
+                    associate(target => targets(size(targets))%ptr)
+
+                    ! Linker-only flags are necessary on some compilers for codes with non-Fortran main
+                    select case (exe_type)
+                       case (FPM_TARGET_C_OBJECT)
+                            call model%compiler%get_main_flags("c",compile_flags)
+                       case (FPM_TARGET_CPP_OBJECT)
+                            call model%compiler%get_main_flags("c++",compile_flags)
+                       case default
+                            compile_flags = ""
+                    end select
+                    target%compile_flags = target%compile_flags//' '//compile_flags
+
                     ! Executable depends on object
-                    call add_dependency(targets(size(targets))%ptr, targets(size(targets)-1)%ptr)
+                    call add_dependency(target, targets(size(targets)-1)%ptr)
 
                     if (with_lib) then
                         ! Executable depends on library
-                        call add_dependency(targets(size(targets))%ptr, targets(1)%ptr)
+                        call add_dependency(target, targets(1)%ptr)
                     end if
 
+                    endassociate
+
                 end select
 
             end do
@@ -385,7 +400,7 @@ subroutine collect_exe_link_dependencies(targets)
                             dep%source%unit_type /= FPM_UNIT_MODULE .and. &
                             index(dirname(dep%source%file_name), exe_source_dir) == 1) then
 
-                            call add_dependency(exe, dep) 
+                            call add_dependency(exe, dep)
 
                         end if
 
@@ -583,13 +598,13 @@ subroutine prune_build_targets(targets, root_package)
     type(build_target_ptr), intent(inout), allocatable :: targets(:)
 
     !> Name of root package
-    character(*), intent(in) :: root_package 
+    character(*), intent(in) :: root_package
 
     integer :: i, j, nexec
     type(string_t), allocatable :: modules_used(:)
     logical :: exclude_target(size(targets))
     logical, allocatable :: exclude_from_archive(:)
-    
+
     if (size(targets) < 1) then
         return
     end if
@@ -599,7 +614,7 @@ subroutine prune_build_targets(targets, root_package)
 
     ! Enumerate modules used by executables, non-module subprograms and their dependencies
     do i=1,size(targets)
-            
+
         if (targets(i)%ptr%target_type == FPM_TARGET_EXECUTABLE) then
 
             nexec = nexec + 1
@@ -620,16 +635,16 @@ subroutine prune_build_targets(targets, root_package)
     ! If there aren't any executables, then prune
     !  based on modules used in root package
     if (nexec < 1) then
-        
+
         do i=1,size(targets)
-            
+
             if (targets(i)%ptr%package_name == root_package .and. &
                  targets(i)%ptr%target_type /= FPM_TARGET_ARCHIVE) then
-    
+
                 call collect_used_modules(targets(i)%ptr)
-    
+
             end if
-            
+
         end do
 
     end if
@@ -651,11 +666,11 @@ subroutine prune_build_targets(targets, root_package)
                     do j=1,size(target%source%modules_provided)
 
                         if (target%source%modules_provided(j)%s .in. modules_used) then
-                            
+
                             exclude_target(i) = .false.
                             target%skip = .false.
 
-                        end if 
+                        end if
 
                     end do
 
@@ -667,11 +682,11 @@ subroutine prune_build_targets(targets, root_package)
                     do j=1,size(target%source%parent_modules)
 
                         if (target%source%parent_modules(j)%s .in. modules_used) then
-                            
+
                             exclude_target(i) = .false.
                             target%skip = .false.
 
-                        end if 
+                        end if
 
                     end do
 
@@ -684,7 +699,7 @@ subroutine prune_build_targets(targets, root_package)
                 target%skip = .false.
             end if
 
-        end associate        
+        end associate
     end do
 
     targets = pack(targets,.not.exclude_target)
@@ -809,20 +824,30 @@ subroutine resolve_target_linking(targets, model)
     do i=1,size(targets)
 
         associate(target => targets(i)%ptr)
+
+            ! May have been previously allocated
+            if (.not.allocated(target%compile_flags)) allocate(character(len=0) :: target%compile_flags)
+
+            target%compile_flags = target%compile_flags//' '
+
             if (target%target_type /= FPM_TARGET_C_OBJECT .and. target%target_type /= FPM_TARGET_CPP_OBJECT) then
-                target%compile_flags = model%fortran_compile_flags &
+                target%compile_flags = target%compile_flags//model%fortran_compile_flags &
                     & // get_feature_flags(model%compiler, target%features)
             else if (target%target_type == FPM_TARGET_C_OBJECT) then
-                target%compile_flags = model%c_compile_flags
+                target%compile_flags = target%compile_flags//model%c_compile_flags
             else if(target%target_type == FPM_TARGET_CPP_OBJECT) then
-                target%compile_flags = model%cxx_compile_flags
+                target%compile_flags = target%compile_flags//model%cxx_compile_flags
             end if
 
+            ! If the main program is a C/C++ one, Intel compilers require additional
+            ! linking flag -nofor-main to avoid a "duplicate main" error, see
+            ! https://stackoverflow.com/questions/36221612/p3dfft-compilation-ifort-compiler-error-multiple-definiton-of-main
+
             !> Get macros as flags.
             target%compile_flags = target%compile_flags // get_macros(model%compiler%id, &
                                                             target%macros, &
                                                             target%version)
- 
+
             if (len(global_include_flags) > 0) then
                 target%compile_flags = target%compile_flags//global_include_flags
             end if
