Passing an allocatable array to a subroutine gives 'signal SIGSEGV, Segmentation fault' error

I have an array sort_cent which is a two dimensional array and unallocated initially. When I call the subroutine rbind by call subroutine rbind(sort_cent,tmparray([arg],:)) , which modifies the array in its values and size, signal SIGSEGV is called and the program interupts. However, the subroutine does reaches at the end as it prints the value "End of the function" after compilation. I guess there is problem in returning the array. Here is the code:

module triangulate

implicit none
contains

subroutine rbind(a,b) 
! combine matrices a and b by row
real, intent(in)  :: b(:,:)
real,intent(inout),allocatable::a(:,:)
real, allocatable :: ab(:,:)
integer              :: n1a,n1,n2,i,err


if(.not. allocated(a)) then
n2 = size(b,2)

n1a = 0
n1 = n1a + size(b,1)
allocate (ab(n1,n2))
print*,shape(ab),n1a
! if(n1a .ne. 0) then
! ! ab(:n1a,:)   = a
! ab(1:n1a,:)   = a
! ab(n1a+1:,:) = b
 
! else
 ab(n1a+1:,:) = b

 allocate(a,source=ab)

!  print*,a

 if (allocated(ab)) deallocate(ab, stat=err)
 if (err /= 0) print *, "ab: Deallocation request denied"

! endif

else

print*,"In the else part"
n2 = size(b,2)
! if (size(b,2) /= n2) stop "need size(a,2) == size(b,2)"
n1a = size(a,1)
n1 = n1a + size(b,1)
allocate (ab(n1,n2))
print*,shape(ab),n1a
! if(n1a .ne. 0) then
! ab(:n1a,:)   = a
ab(1:n1a,:)   = a
ab(n1a+1:,:) = b
 
deallocate(a)
allocate(a,source=ab)
deallocate(ab)

endif
! call MOVE_ALLOC(ab,a)

do i=1,size(a,1)
print*,a(i,:)
end do

print*,shape(a)
print*,"End of the function"

! deallocate(a)
! return
end subroutine rbind

end module

And the subroutine which calls the above subroutine is:

subroutine sortanticlockwise(triangle,c,coord,sort_cent)

real,intent(in)::coord(:,:)
integer,intent(in)::triangle(:)
real,allocatable,intent(inout)::sort_cent(:,:)
integer,intent(in)::c(:)
real,allocatable::tmparray(:,:),tmp(:,:)
integer::i,j,k,ISTAT
real::pi
real,allocatable::dist(:)
real ,allocatable::angles(:)
real::center(1,2)
integer,allocatable::arg(:)
center=reshape([1,0], shape=[1,2])
pi=4*atan(1.0)

! allocate(sort_cent(0,2), STAT = ISTAT )
! IF ( ISTAT .NE. 0 ) THEN
! WRITE( *, '( A, I10)' ) 'Buffer allocation failed: STAT=', ISTAT
! STOP
! END IF


j=0
do i=1,1
  allocate(tmparray(size(triangle(j+1:c(i)+j)),2))
  ! allocate(tmp(size(triangle(j+1:c(i)+j)),2))  !!Fixed
  ! print*,size(triangle(j+1:c(i)+j))

  tmparray=coord([triangle(j+1:c(i)+j)],:) ! * Fixed
  j=j+c(i)
  ! print*,size(tmparray)

  allocate(dist(size(tmparray,1)))
  allocate(angles(size(tmparray,1)))
  allocate(arg(size(tmparray,1)))



  dist=norm2(tmparray-spread(center(1,:),1,size(tmparray,1)),2)  ! *Correct till here


  where (tmparray(:,2) >0 ) 
  angles= acos((tmparray(:,1)-1)/dist)
  elsewhere
  angles= 2*pi- acos((tmparray(:,1)-1)/dist)
    
  end where

  ! arg=argsort(angles)
  arg=argsort(angles)  

!!!!!
open(103,file='angles1.out', status='replace', action='write')

do k=1, size(arg)
write(103,*) arg(k)
end do
close(103)


!!!!

print*,allocated(sort_cent)



 call rbind(sort_cent,tmparray([arg],:))
   print*,"Correct"



  deallocate(tmparray)
  deallocate(dist)
  deallocate(angles)
  deallocate(arg)

enddo

  
  
end subroutine sortanticlockwise

The output is:

F
         249           2           0
   1.14597142       3.33256181E-03
   1.14644611       6.66513247E-03
   1.14643490       1.33300433E-02
   1.14594853       1.66623611E-02
   1.14608729       2.33216006E-02
   1.14546788       2.66483724E-02
   1.14534485       3.32915969E-02

   .
   .
   .

   .

     1.14571607      -3.33803333E-03
         249           2
 End of the function

Program received signal SIGSEGV: Segmentation fault - invalid memory reference.

Backtrace for this error:
#0  0x7f8d8ea23ad0 in ???
#1  0x7f8d8ea22c35 in ???
#2  0x7f8d8e63bcef in ???
        at ./signal/../sysdeps/unix/sysv/linux/x86_64/libc_sigaction.c:0
#3  0x7f8d8e6a09d9 in arena_for_chunk
        at ./malloc/arena.c:162
#4  0x7f8d8e6a09d9 in arena_for_chunk
        at ./malloc/arena.c:160
#5  0x7f8d8e6a09d9 in __GI___libc_free
        at ./malloc/malloc.c:3384
#6  0x55ccfb1a696c in sortanticlockwise
        at /home/abhishek/abhishektiwari/test.f90:156
#7  0x55ccfb1a49f6 in test
        at /home/abhishek/abhishektiwari/test.f90:69
#8  0x55ccfb1a6c08 in main
        at /home/abhishek/abhishektiwari/test.f90:3
Segmentation fault (core dumped)

Further, the above subroutine is again called by the line in main as:

real,dimension(:,:),allocatable :: sorted_centroid
.
.
.
.
call sortanticlockwise(trianglesinsurface,c3,coord,sorted_centroid)

I am using gcompiler latest version to compile the above program. The fortran version is also latest.

I tried suggestions on this, this and numerous others. However, I still kept gettting the error after implementing the solutions in the above websites. Can anyone help?