use no-overhead C function

Author: perazz

src/stdlib_system.F90

@@ -1,6 +1,7 @@
 module stdlib_system
-use, intrinsic :: iso_c_binding, only : c_int, c_long, c_null_ptr, c_int64_t
-use stdlib_kinds, only: int64, dp
+use, intrinsic :: iso_c_binding, only : c_int, c_long, c_ptr, c_null_ptr, c_int64_t, c_size_t, &
+    c_f_pointer
+use stdlib_kinds, only: int64, dp, c_char
 implicit none
 private
 public :: sleep
@@ -635,17 +636,39 @@ pure function OS_NAME(os)
     end select
 end function OS_NAME
 
-!> Return the file path of the null device for the current operating system.
+!> Returns the file path of the null device for the current operating system.
+!>
+!> Version: Helper function.
 function null_device() result(path)
     !> File path of the null device
     character(:), allocatable :: path
 
-    if (OS_TYPE()==OS_WINDOWS) then 
-        path = 'NUL'
-    else
-        path = '/dev/null'
-    end if
+    interface
+    
+        ! No-overhead return path to the null device
+        type(c_ptr) function process_null_device(len) bind(C,name='process_null_device')
+            import c_ptr, c_size_t    
+            implicit none
+            integer(c_size_t), intent(out) :: len
+        end function process_null_device    
+        
+    end interface
 
+    integer(c_size_t) :: i, len
+    type(c_ptr) :: c_path_ptr
+    character(kind=c_char), pointer :: c_path(:)    
+
+    ! Call the C function to get the null device path and its length
+    c_path_ptr = process_null_device(len)
+    call c_f_pointer(c_path_ptr,c_path,[len])
+
+    ! Allocate the Fortran string with the length returned from C
+    allocate(character(len=len) :: path)
+        
+    do concurrent (i=1:len)
+        path(i:i) = c_path(i)
+    end do
+        
 end function null_device
 
 end module stdlib_system

src/stdlib_system_subprocess.F90

@@ -51,13 +51,6 @@ subroutine process_wait(seconds) bind(C,name='process_wait')
             real(c_float), intent(in), value :: seconds
         end subroutine process_wait            
 
-        ! Return path to the null device
-        type(c_ptr) function process_null_device(len) bind(C,name='process_null_device')
-            import c_ptr, c_int    
-            implicit none
-            integer(c_int), intent(out) :: len
-        end function process_null_device
-        
         ! Utility: check if _WIN32 is defined in the C compiler
         logical(c_bool) function process_is_windows() bind(C,name='process_is_windows')
             import c_bool
@@ -604,29 +597,6 @@ function assemble_cmd(args, stdin, stdout, stderr) result(cmd)
 
     end function assemble_cmd            
 
-    !> Returns the file path of the null device for the current operating system.
-    !>
-    !> Version: Helper function.
-    function null_device() 
-        character(:), allocatable :: null_device
-        
-        integer(c_int) :: i, len
-        type(c_ptr) :: c_path_ptr
-        character(kind=c_char), pointer :: c_path(:)
-        
-        ! Call the C function to get the null device path and its length
-        c_path_ptr = process_null_device(len)
-        call c_f_pointer(c_path_ptr,c_path,[len])
-
-        ! Allocate the Fortran string with the length returned from C
-        allocate(character(len=len) :: null_device)
-        
-        do concurrent (i=1:len)
-            null_device(i:i) = c_path(i)
-        end do
-        
-    end function null_device
-    
     !> Returns the file path of the null device for the current operating system.
     !>
     !> Version: Helper function.

src/stdlib_system_subprocess.c

@@ -376,7 +376,7 @@ void process_wait(float seconds)
 }
 
 // Returns the cross-platform file path of the null device for the current operating system.
-const char* process_null_device(int* len) 
+const char* process_null_device(size_t* len) 
 {
 #ifdef _WIN32    
         (*len) = strlen("NUL");