notes

把pascal程序转成C语言程序 把pascal程序转成C语言程序

THE GRAND P2C NOTES FILE:

This file contains notes to myself recording bugs, flaws, and suggested
improvements to p2c.  They have roughly been separated into "old", "older",
and "oldest" groups.  I can't guarantee I'll do any of these.  If you do,
please mail me the diffs so I can incorporate them into the next release.
Thanks!
						-- Dave Gillespie
						   [e-mail]

-----------------------------------------------------------------------------

   Handling of comments that trail the ELSE clause of an IF statement
   could use some work.

-----------------------------------------------------------------------------

   Technically speaking, "for byte := min to max do" is legal even
   if min > 255, i.e., the limits only need to be in range if the
   body of the loop executes.  Thus, FOR loops should really use a
   shadow parameter not just when max is the constant 255, but
   whenever min or max are not provably in byte range.

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   Have a "-M"-like mode in which FREE is suppressed altogether, useful
   in case p2c crashes because bugs have corrupted malloc's free list.

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   For expressions building small-sets whose maximum element is <= 15,
   use "1 << x" instead of "1L << x".

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   Handle VAX Pascal VARYING OF CHARs used as the arguments of WITH
   statements.

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   StringTruncLimit would be helped by expr.c:strmax() interpreting
   sprintf control strings.  For %s, use strmax of the corresponding
   argument.  For %d, use 11, etc.  For %.10s, use min(10, strmax(arg)).
   For %.*s, just use strmax(arg), I guess.

   Have a mode in which such assignments are automatically truncated.

   Perform truncation testing for non-VAR procedure arguments, too.

-----------------------------------------------------------------------------

   In cref.p, the "strappend(buf,#0)" statement translates into
   "strcpy(STR1,buf); strcpy(buf,STR1)" with a warning about a null
   character in a sprintf control string!

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   Still having problems where the opening comment of an imported
   module's interface text is copied into the program.

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   VAX Pascal features not yet handled:

      [UNSAFE] attribute is only implemented in a few situations.
      [UNBOUND] attribute on a procedure says it doesn't need a static link.
      [TRUNCATE] attribute on a parameter allows optional params w/no default.
      [LIST] attribute on a parameter is like &rest in Lisp.
      Support types like, e.g., [LONG] BOOLEAN.
      Can assign "structurally compatible" but different record types.
      File intrinsics need serious work, especially OPEN.
      If a copy param is [READONLY], don't need to copy it.
      If a procedure is [ASYNCHRONOUS], make all its variables volatile.
      If a procedure is [NOOPTIMIZE], make all its variables volatile.
      Provide a real implementation of BIN function and :BIN read format.
      BIT_OFFSET and CARD intrinsics are not supported.

-----------------------------------------------------------------------------

   Modula-2 features not yet handled:

      Local modules are faked up in a pretty superficial way.
      WORD is compatible with both pointers and CARDINALs.
      WORD parameters are compatible with any word-sized object.
      ARRAY OF WORD parameters are compatible with absolutely anything.
      Improve treatment of character strings.
      Find manuals for real implementations of Modula-2 and implement
         any common language extensions.
      Fix p2c to read system.m2 instead of system.imp automatically.

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   Oregon Software Pascal features not yet handled:

	procedure noioerror(var f:file);
		Built-in.  Sets a flag on an already-open file so that
		I/O errors record an error code rather than crashing.
		Each file has its own error code.

	function ioerror(var f:file) : boolean;
		True if an error has occurred in the file.

	function iostatus(var f:file) : integer;
		The error code, when ioerror was true.

	reset and rewrite ignore the third parameter, and allow a fourth
	param which is an integer variable that receives a status code.
	Without this param, open errors are fatal.  An optional param
	may be omitted as in reset(f,'foo',,v);

-----------------------------------------------------------------------------

   In p_search, if a file contains const/var/type/procedure/function
   declarations without any module declaration, surround the entire
   file with an implicit "module <generated-name>; {PERMANENT}" ... "end.".
   This would help the Oregon Software dialect considerably.

-----------------------------------------------------------------------------

   Provide an explicit IncludeFrom syntax for "no include file".
   E.g., "IncludeFrom dos 0".

-----------------------------------------------------------------------------

   In docast, smallsets are converted to large sets of the requested type.
   Wouldn't it be better to convert to a set of 0..31 of the base type?
   This would keep foo([]), where the argument is "set of char", from
   allocating a full 256-bit array for the temporary.

-----------------------------------------------------------------------------

   When initializing a constant variant record or array of same in which
   non-first variants are initialized, create a function to do the
   initialization, plus, for modules w/o initializers, a note to call
   this function.  Another possibility:  Initialize the array as well as
   possible, but leave zeros in the variant parts.  Then the function
   has only to fix up the non-first variant fields.

-----------------------------------------------------------------------------

   Figure out some way to initialize packed array constants, e.g., a short
   macro PACK4(x,y)=(((x)<<4)+(y)) which is used inside the C initializer.
   Alternatively, implement initializer functions as above and use those.

-----------------------------------------------------------------------------

   How about declaring Volatile any variables local to a function which
   are used after the first RECOVER?  GNU also suggests writing the
   statement:  "&foo;" which will have no side effect except to make
   foo essentially volatile, without relying on ANSI features.

-----------------------------------------------------------------------------

   Test the macros for GET, PUT, etc.

-----------------------------------------------------------------------------

   Can the #if 0'd code for strinsert in funcs.c be changed to test
   strcpyleft?

-----------------------------------------------------------------------------

   Even in Ansi mode, p2c seems to be casting Anyptrs into other pointer
   types explicitly.  This is an automatic conversion in Ansi C.

-----------------------------------------------------------------------------

   A Turbo typed constant or VAX initialized variable with a VarMacro
   loses its initializer!

-----------------------------------------------------------------------------

   Test the ability of the parser to recover from common problems such
   as too many/few arguments to a procedure, missing/extra semicolon, etc.
   One major problem has been with undeclared identifiers being used as
   type names.

-----------------------------------------------------------------------------

   Line breaker still needs considerable tuning!

-----------------------------------------------------------------------------

   How about indenting trailing comments analogously to the code:
   Try to indent to column C+(X-Y), where C=original column number,
   X=output indentation, Y=original input indentation.

   Even fancier would be to study all the comment indentations in the
   function or struct decl to discover if most comments are at the same
   absolute indentation; if so, compute the average or minimum amount of
   space preceding the comments and indent the C comments to an analogous
   position.

-----------------------------------------------------------------------------

   Warn if address is taken of an arithmetic expression like "v1+1".
   Allow user to declare certain bicalls as l-values, e.g., so that
   LSC's topLeft and botRight macros won't generate complaints.

-----------------------------------------------------------------------------

   Consider changing the "language" modes into a set of p2crc files
   which can be included to support the various modes.

-----------------------------------------------------------------------------

   If we exchange the THEN and ELSE parts of an IF statement, be sure
   to exchange their comments as well!

-----------------------------------------------------------------------------

   How about checking for a ".p2crc" file in the user's home directory.

-----------------------------------------------------------------------------

   Store comments in the following situations:
      On the first line of a record decl.
      On the default clause of a CASE statement
        (use same trick as for ELSE clauses).
      On the "end" of a CASE statement.
      On null statements.
      Use stealcomments for, e.g., decl_comments and others.

-----------------------------------------------------------------------------

   Think of other formatting options for format_gen to support.

-----------------------------------------------------------------------------

   Consider converting gratuitous BEGIN/END pairs into gratuitous
   { } pairs.

-----------------------------------------------------------------------------

   The construction "s := copy(s, 1, 3)" converts to a big mess that
   could be simplified to "s[3] = 0".

-----------------------------------------------------------------------------

   Have a mode (and make it the default!) in which declarations are mixed
   if and only if the original Pascal decls were mixed.  Simply store
   a flag in each meaning to mark "mixed-with-preceding-meaning".