Dangling pointers

Dangling pointers are easily created when using the TextIO package, because WRITELINE de-allocates the access type (pointer) that is passed to it. Following are examples of good and bad VHDL coding styles:

Bad VHDL (because L1 and L2 both point to the same buffer):

READLINE (infile, L1);    -- Read and allocate buffer
L2 := L1;                 -- Copy pointers
WRITELINE (outfile, L1);  -- Deallocate buffer 

Good VHDL (because L1 and L2 point to different buffers):

READLINE (infile, L1);      -- Read and allocate buffer
L2 := new string'(L1.all);  -- Copy contents
WRITELINE (outfile, L1);    -- Deallocate buffer 

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