Allow usage of response files with ar

Author: awvwgk

src/fpm_backend.f90

@@ -33,7 +33,7 @@ module fpm_backend
 use fpm_targets, only: build_target_t, build_target_ptr, &
                      FPM_TARGET_OBJECT, FPM_TARGET_ARCHIVE, FPM_TARGET_EXECUTABLE
 
-use fpm_strings, only: string_cat
+use fpm_strings, only: string_t
 
 implicit none
 
@@ -247,7 +247,8 @@ subroutine build_target(model,target)
               //" "//target%link_flags// " -o " // target%output_file)
 
     case (FPM_TARGET_ARCHIVE)
-        call run("ar -rs " // target%output_file // " " // string_cat(target%link_objects," "))
+        call write_response_file(target%output_file//".resp" ,target%link_objects)
+        call run("ar -rs " // target%output_file // " @" // target%output_file//".resp")
 
     end select
 
@@ -259,4 +260,19 @@ subroutine build_target(model,target)
 
 end subroutine build_target
 
+!> Response files allow to read command line options from files.
+!> Whitespace is used to separate the arguments, we will use newlines
+!> as separator to create readable response files which can be inspected
+!> in case of errors.
+subroutine write_response_file(name, argv)
+    character(len=*), intent(in) :: name
+    type(string_t), intent(in) :: argv(:)
+    integer :: iarg, io
+    open(file=name, newunit=io)
+    do iarg = 1, size(argv)
+        write(io, '(a)') argv(iarg)%s
+    end do
+    close(io)
+end subroutine write_response_file
+
 end module fpm_backend