* Makefile.in:

	(GNAT_ADA_OBJS): add g-crc32.o, a-tags.o, a-stream.o
	(GNATBIND_OBJS): add g-crc32.o, a-tags.o, a-stream.o
	(GNATLS_RTL_OBJS): add g-crc32.o
	(GNATMAKE_RTL_OBJS): add g-crc32.o

	* ali-util.adb:
	(CRC_Match): new function.
	(Get_File_Checksum): renamed Get_File_CRC. Use the GNAT.CRC32 unit
	instead of the previous simple checksum algorithm.
	(Time_Stamp_Mismatch): use CRC_Match for comparison.
	(Set_Source_Table): idem.

	* ali-util.ads:
	(Get_File_Checksum): renamed Get_File_CRC as now we compute CRC
	instead of simple checksum.
	(CRC_Match): new function.
	(CRC_Error): new constant.

	* ali.adb (Scan_ALI): rename variable Chk to CRC as we are handling
	a CRC now and not a simple checksum. A CRC uses lower-case hex
	letters, fixes ambiguity in parsing.

	* ali.ads (Sdep_Record.Checksum): renamed Sdep_Record.CRC as this
	is what this variable will store.

	* bcheck.adb: Change reference to chechsum in comments by CRC.
	(Check_Consistency): Rename Get_File_Checksum to Get_File_CRC.
	rename All_Checksum_Match to All_CRC_Match. Change due to API
	renaming since now GNAT does not use a simple checksum but a
	CRC using GNAT.CRC32.

	* gnatls.adb: Rename Checksum to CRC in many places, we use a CRC
	now and not anymore a simple checksum.

	* lib-load.adb: Use Source_CRC instead of Source_Checksum in many
	places.

	* lib-writ.adb (Write_ALI): Use Source_CRC instead of Source_Checksum.

	* scans.adb:
	(Restore_Scan_State): rename Checksum to CRC.
	(Save_Scan_State): idem.

	* scans.ads:
	With GNAT.CRC32.
	(Checksum): rename to CRC.
	(Saved_Scan_State): Save_Checksum field renamed to Save_CRC

	* scn-nlit.adb: Rename many Accumulate_Checksum to Update (from
	GNAT.CRC32).  Update copyright notice.

	* scn-slit.adb: Rename many Accumulate_Checksum to Update (from
	GNAT.CRC32).  Update copyright notice.

	* scn.adb:
	(Accumulate_Checksum): removed.
	(Update): new procedure. Add a wide-character into the CRC.

	* sinput-l.adb:
	(Complete_Source_File_Entry): use CRC32 instead of simple checksum.
	(Load_File): fix initialization of S (change Source_Checksum to
	Source_CRC)

	* sinput-p.adb (Load_Project_File): rename Source_Checksum to
	Source_CRC in S initialization.

	* sinput.adb (Source_Checksum): renamed to Source_CRC.

	* sinput.ads (Source_Checksum): renamed to Source_CRC.
	Update comments for the CRC.

	* types.adb (Hex): Use lowercase for the letter part.

	* types.ads (Get_Hex_String): Returns the hexadecimal representation
	for a word. This is currently used only for CRC. In previous version,
	the checksum was using a representation with all letter being
	upper-case. With the new implementation (using CRC) we do not remove
	the 32th bit of the CRC, so we can have an upper-case starting letter
	in the CRC. This is not possible to parse in Scan_ALI (ali.adb).
	It is ambigous since the CRC was optional and could be followed by
	options like EB, EE. So now this routines uses lower-case letter for
	the hexadecimal representation. Strange enough only lower case letters
	where checked in Scan_ALI (even if this was not a possible case).

	* gnatvsn.ads (Library_Version): changed to 3.15a.

	* s-crc32.ads: Initial version from GNAT.CRC32. This is the version
	for the compiler.

	* s-crc32.adb: Initial version from GNAT.CRC32. This is the version
	for the compiler.

	* ali-util.adb: Redo previous change to avoid using word CRC everywhere
	Add 2001 to copyright notice
	(Accumulate_Checksum): Modify to use System.CRC32.

	* ali-util.ads: Redo changes of previous revision to continue to use
	the word Checksum. Add 2001 to copyright notice.

	* ali.adb: Undo some of previous changes, not needed.
	Keep the change for lower case letters in the checksum.

	* ali.ads: Undo previous change not needed.

	* bcheck.adb: Undo most of previous change, not needed.
	But do use Checksums_Match for checksum comparison.

	* gnatls.adb: Undo most of previous change, not needed.
	But do use Checksums_Match for comparing checksums.

	* lib-load.adb: Undo previous change, not needed.

	* lib-writ.adb: Undo previous change, not needed.

	* lib-writ.ads: Document that checksums use lower case,
	not upper case letters.

	* scans.adb: Undo previous change, not needed

	* scans.ads: Undo previous change, not needed.

	* scn-nlit.adb: Undo previous changes, not needed.

	* scn-slit.adb: Undo previous change, not needed.  Fix header format.

	* scn.adb:
	(Accumulate_Checksum): Use System.CRC32.
	(Initialize_Checksum): New procedure.
	Remove other changes of previous revision.

	* sinput-p.adb: Undo previous change, not needed.

	* sinput.adb: Undo previous change, not needed.

	* sinput-l.adb: Undo previous change, not needed.

	* sinput.ads: Undo previous change, not needed.  Keep only comment
	on new checksum algorithm

	* Makefile.in: Add s-crc32 as needed, remove g-crc32.
	Also remove a-tags and a-stream from GNAT sources.

	* ali.adb (Scan_ALI): fix typo introduce in latest check-in.

	* Makefile.in (GNATRTL_NONTASKING_OBJS): Add g-crc32.o.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@46206 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 7 insertions, 23 deletions

diff --git a/gcc/ada/sinput.ads b/gcc/ada/sinput.ads
index 585a8b95ea0..b842790bc10 100644
--- a/gcc/ada/sinput.ads
+++ b/gcc/ada/sinput.ads
@@ -6,7 +6,7 @@
 --                                                                          --
 --                                 S p e c                                  --
 --                                                                          --
---                            $Revision: 1.69 $
+--                            $Revision$
 --                                                                          --
 --          Copyright (C) 1992-2001 Free Software Foundation, Inc.          --
 --                                                                          --
@@ -274,34 +274,18 @@ package Sinput is
    --  minus-minus sequence starting a comment, and all control characters
    --  except ESC.
 
-   --  These characters are used to compute a 31-bit checksum which is stored
-   --  in the variable Scans.Checksum, as follows:
-
-   --    If a character, C, is not part of a wide character sequence, then
-   --    either the character itself, or its lower case equivalent if it
-   --    is a letter outside a string literal is used in the computation:
-
-   --      Checksum := Checksum + Checksum + Character'Pos (C);
-   --      if Checksum > 16#8000_0000# then
-   --         Checksum := (Checksum + 1) and 16#7FFF_FFFF#;
-   --      end if;
-
-   --    For a wide character sequence, the checksum is computed using the
-   --    corresponding character code value C, as follows:
-
-   --      Checksum := Checksum + Checksum + Char_Code'Pos (C);
-   --      if Checksum > 16#8000_0000# then
-   --         Checksum := (Checksum + 1) and 16#7FFF_FFFF#;
-   --      end if;
+   --  The checksum algorithm used is the standard CRC-32 algorithm, as
+   --  implemented by System.CRC32, except that we do not bother with the
+   --  final XOR with all 1 bits.
 
    --  This algorithm ensures that the checksum includes all semantically
    --  significant aspects of the program represented by the source file,
    --  but is insensitive to layout, presence or contents of comments, wide
    --  character representation method, or casing conventions outside strings.
 
-   --  Scans.Checksum is initialized to zero at the start of scanning a file,
-   --  and copied into the Source_Checksum field of the file table entry when
-   --  the end of file is encountered.
+   --  Scans.Checksum is initialized appropriately at the start of scanning
+   --  a file, and copied into the Source_Checksum field of the file table
+   --  entry when the end of file is encountered.
 
    -------------------------------------
    -- Handling Generic Instantiations --