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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT RUN-TIME COMPONENTS --
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4 -- --
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5 -- S Y S T E M . M E M O R Y --
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6 -- --
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7 -- S p e c --
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8 -- --
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145
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9 -- Copyright (C) 2001-2019, Free Software Foundation, Inc. --
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111
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10 -- --
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11 -- GNAT is free software; you can redistribute it and/or modify it under --
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12 -- terms of the GNU General Public License as published by the Free Soft- --
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13 -- ware Foundation; either version 3, or (at your option) any later ver- --
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14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
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17 -- --
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18 -- As a special exception under Section 7 of GPL version 3, you are granted --
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19 -- additional permissions described in the GCC Runtime Library Exception, --
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20 -- version 3.1, as published by the Free Software Foundation. --
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21 -- --
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22 -- You should have received a copy of the GNU General Public License and --
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23 -- a copy of the GCC Runtime Library Exception along with this program; --
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24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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25 -- <http://www.gnu.org/licenses/>. --
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26 -- --
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27 -- GNAT was originally developed by the GNAT team at New York University. --
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28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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29 -- --
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30 ------------------------------------------------------------------------------
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31
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32 -- This package provides the low level memory allocation/deallocation
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33 -- mechanisms used by GNAT.
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34
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35 -- To provide an alternate implementation, simply recompile the modified
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36 -- body of this package with gnatmake -u -a -g s-memory.adb and make sure
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37 -- that the ali and object files for this unit are found in the object
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38 -- search path.
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39
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40 -- This unit may be used directly from an application program by providing
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41 -- an appropriate WITH, and the interface can be expected to remain stable.
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42
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43 pragma Compiler_Unit_Warning;
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44
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45 package System.Memory is
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46 pragma Elaborate_Body;
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47
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48 type size_t is mod 2 ** Standard'Address_Size;
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49 -- Note: the reason we redefine this here instead of using the
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50 -- definition in Interfaces.C is that we do not want to drag in
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51 -- all of Interfaces.C just because System.Memory is used.
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52
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53 function Alloc (Size : size_t) return System.Address;
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54 -- This is the low level allocation routine. Given a size in storage
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55 -- units, it returns the address of a maximally aligned block of
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56 -- memory. The implementation of this routine is guaranteed to be
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57 -- task safe, and also aborts are deferred if necessary.
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58 --
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59 -- If Size is set to size_t'Last on entry, then a Storage_Error
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60 -- exception is raised with a message "object too large".
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61 --
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62 -- If Size is set to zero on entry, then a minimal (but non-zero)
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63 -- size block is allocated.
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64 --
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65 -- Note: this is roughly equivalent to the standard C malloc call
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66 -- with the additional semantics as described above.
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67
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68 procedure Free (Ptr : System.Address);
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69 -- This is the low level free routine. It frees a block previously
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70 -- allocated with a call to Alloc. As in the case of Alloc, this
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71 -- call is guaranteed task safe, and aborts are deferred.
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72 --
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73 -- Note: this is roughly equivalent to the standard C free call
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74 -- with the additional semantics as described above.
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75
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76 function Realloc
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77 (Ptr : System.Address;
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78 Size : size_t) return System.Address;
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79 -- This is the low level reallocation routine. It takes an existing
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80 -- block address returned by a previous call to Alloc or Realloc,
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81 -- and reallocates the block. The size can either be increased or
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82 -- decreased. If possible the reallocation is done in place, so that
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83 -- the returned result is the same as the value of Ptr on entry.
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84 -- However, it may be necessary to relocate the block to another
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85 -- address, in which case the information is copied to the new
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86 -- block, and the old block is freed. The implementation of this
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87 -- routine is guaranteed to be task safe, and also aborts are
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88 -- deferred as necessary.
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89 --
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90 -- If Size is set to size_t'Last on entry, then a Storage_Error
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91 -- exception is raised with a message "object too large".
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92 --
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93 -- If Size is set to zero on entry, then a minimal (but non-zero)
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94 -- size block is allocated.
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95 --
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96 -- Note: this is roughly equivalent to the standard C realloc call
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97 -- with the additional semantics as described above.
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98
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99 private
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100
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101 -- The following names are used from the generated compiler code
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102
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103 pragma Export (C, Alloc, "__gnat_malloc");
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104 pragma Export (C, Free, "__gnat_free");
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105 pragma Export (C, Realloc, "__gnat_realloc");
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106
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107 end System.Memory;
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