April 2005 - Gpc

Inefficiency of `mod'
by Emil Jerabek 25 Oct '10

25 Oct '10

Hi, during some debugging I noticed that GPC generates very hairy code for the `mod' operator with signed arguments. A closer look revealed that the code contains a lot of branching on conditions which can be determined on compile time, and most surprisingly, the value of X mod Y is recomputed _twice_, if X is negative. (I've attached a commented assembler dump.) This may be partially a back-end problem (CSE?), but I feel there's something wrong in the relevant code in gpc-common.c (build_pascal_binary_op) as well. `exp1 mod exp2' gets translated into something like exp2 <= 0 ? error : exp1 >= 0 ? exp1 mod exp2 : ((-exp1) mod exp2) == 0 ? 0 : exp2 - (-exp1) mod exp2 This arranges that both arguments supplied to the "internal mod" are non-negative, but this information is not passed on -- the arguments are still declared as signed types, which apparently makes the back-end to produce the mess it does. I've done a little test: the following replacement for `mod', which differs from the built-in one essentially just by the type-casts to `Cardinal', inline operator xmod (X, Y: Integer) = Z: Integer; begin if Y <= 0 then RuntimeError (714); if X >= 0 then Z := Cardinal (X) mod Y else begin Z := Cardinal (-X) mod Y; if Z <> 0 then Z := Y - Z end end; indeed generates a better code, it measures about 15% faster for positive X and more than twice faster for negative X. YMMV. If this is possible in user code, it should work in the compiler internals as well :) The result type of the whole `mod' expression looks dubious too. IIUIC, `exp1 mod exp2' inherits the type of exp1. Now, the result of `mod' is guaranteed to be nonnegative and to fit in the type of exp2 (or more precisely, it is in 0 .. High (type of (exp2)) - 1), whereas it needn't have anything to do with the type of exp1: consider var X, Z: Integer; Y: LongInt; begin X := -8; Y := High (LongInt); Z := X mod Y { -> overflow } end Or am I missing something? Emil (BTW, where is fjf434c.pas?)

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Passing by reference
by Adriaan van Os 06 Jun '05

06 Jun '05

Another problem, also reported on the macpascal mailing list and reproduced by the following program: [G5:gcc/p/test] adriaan% cat avo12.pas program avo12; type Str255 = record sLength: Byte; sChars: packed array[1..255] of char; end; function StringToStr255 ( const s: String ) = Result : Str255; begin Result.sLength := Min( Length( s ), 255 ); if Result.sLength > 0 then begin Result.sChars[1..Result.sLength] := s[1..Result.sLength]; end; end; procedure DrawString1( const s: Str255); external name 'DrawString'; procedure DrawString2( protected var s: Str255); external name 'DrawString'; begin DrawString1( StringToStr255( 'Hello')); {OK} DrawString2( StringToStr255( 'Hello')) {Error: reference expected, value given} end. [G5:gcc/p/test] adriaan% gpc avo12.pas avo12.pas: In main program: avo12.pas:19: error: reference expected, value given In gpc-20030830, this was no problem, but now it is no longer allowed, which is quite inconvenient. In the GPC interfaces for Mac OS X, we use the external declaration form with a "protected var" because (according to the gc docs) the "const" declaration form doesn't guarantuee that the parameter is passed by reference, which is an ABI requirement. Regards, Adriaan van Os

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The CRT Unit
by Alex v.Below 06 Jun '05

06 Jun '05

Hello, I am trying to help students use gpc (on Mac OS X, in particular) instead of TurboPascal, which is still taught in some schools: http://macentwicklerwelt.net/index.php?title=Leben_ohne_TurboPascal (Sorry, German only) However, I have been unsuccessful in getting the CRT Unit to work on OS X: I tried to compile the crtdemo.pas in the demo folder, and after searching the mail archives, tried the --automake option. Neither was successful. Is there any other trick in getting the CRT Unit to work? I installed the binary installation of gpc for OS X. If anyone is interested I will gladly post the error output. I am a pretty skilled OS X coder, but my memory of pascal seems to have faded away... Thanks for your help! Alex

9 20

Temporary web server
by Frank Heckenbach 23 May '05

23 May '05

I've put a copy of the GPC home page on a new web server: http://www2.gnu-pascal.de It is also available on the usual URLs (http://www.gnu-pascal.de etc.), but due to DNS caching it may take a few days until your machine will recognize the change. The mailing list archives are not there yet, and the downloads are missing. Only the latest alpha is there. If some of the contributors would like to put some files there, please PM me at frank(a)g-n-u.de (either send the files directly, even if large, or a URL where I can get them). Frank -- Frank Heckenbach, frank(a)g-n-u.de, http://fjf.gnu.de/, 7977168E GPC To-Do list, latest features, fixed bugs: http://www2.gnu-pascal.de/todo.html GPC download signing key: ACB3 79B2 7EB2 B7A7 EFDE D101 CD02 4C9D 0FE0 E5E8

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-mlong-double-128
by Adriaan van Os 13 May '05

13 May '05

The following produces an internal compiler error: [G4:~/gnu/testgpc/adriaan] adriaan% cat compare.pas program Compare; procedure R ( var r1, r2: real); begin if r1 <> r2 then r1:= r2 - 1.0 end; begin end. [G4:~/gnu/testgpc/adriaan] adriaan% gpc -o compare compare.pas -mlong-double-128 compare.pas: In procedure `R': compare.pas:6: error: unrecognizable insn: (insn 26 34 27 2 0x0 (set (reg:SI 126) (subreg:SI (reg:TF 33 f1) 0)) -1 (nil) (nil)) compare.pas:6: internal compiler error: in extract_insn, at recog.c:2175 It may be, of course, that the Darwin target doesn't properly support the -mlong-double-128 PowerPC processor option. If it's a gcc back-end bug, I can report it to Bugzilla. However, the "real" type used is 64-bit on the Darwin target, with or without -mlong-double-128 ... The option only changes the size of the "longreal" and "extended" types to 128-bit. Regards, Adriaan van Os [G4:~/gnu/testgpc/adriaan] adriaan% gpc -v Reading specs from /Developer/Pascal/gpc33d7/lib/gcc-lib/powerpc-apple-darwin/3.3/specs Configured with: ../gpc-3.3d7/configure --enable-languages=pascal,c --enable-threads=posix --prefix=/Developer/Pascal/gpc33d7 --target=powerpc-apple-darwin Thread model: posix gpc version 20030507, based on gcc-3.3

6 15

bug: ncurses + slackware 10.0, 10.1
by Russell Whitaker 01 May '05

01 May '05

Hi Program below illustrates a bug: lower case a, lower case f thru z, and number 0 are printed with graphic characters. This bug did not appear in earlier versions of slackware. If you make the window with a frame around it, (uncomment the framewin line) the characters are printed normally, and afterwards any window written to is also printed normally. program ncurtest; uses GPC, GPCUtil, CRT, FrameWin; var submenu : WinState; Data : array[1..3] of string( 32 ) = ( 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz', '0123456789'); i : integer; begin i := (ScreenSize.X - 32) div 2; MakeWin( SubMenu, i, 2, i + 32, 7 ); { FrameWin('HELP: hit Enter to exit', DoubleFrame ); } FillWin( ' ', 16 * Blue ); HideCursor; for i := 1 to 3 do WriteStrAt( 2,i, Data[ i ], 16 * Blue + LightGray ); end. Russ Note to support(a)slackware.com, bug-ncurses(a)gnu.org: gpc(a)gnu.de is a pascal mailing list unit CRT is a pascal interface to ncurses

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GPC ALPHA 20050331 released
by Frank Heckenbach 29 Apr '05

29 Apr '05

I have uploaded a new alpha version of GPC to <http://www.gnu-pascal.de/alpha/>. This is an ALPHA version. Not so many extensive tests have been made and the test suite is not expected to pass without errors. I'm not uploading binaries, diffs, separate test suite archives, updated web pages etc., just the source distribution. (Of course, others may feel free to upload binaries for various platforms.) I'm not aware of any serious bugs, but you have to decide for yourself whether to use it for production work. New features: * new options `--[no]-nonlocal-exit' (default in `--ucsd-pascal' and `--mac-pascal') (fjf988[fijk].pas, fjf1062*.pas) (U) (M) * new options `--[no]-object-checking' (on by default) to check on virtual method calls if VMT pointer is not nil and has matching `Size' and `NegatedSize' entries, new options `--[no]-range-and-object-checking' which are now equivalent to `$R[+-]' (fjf1053*.pas) (B) * new options `--[no]-pointer-checking', `--[no]-pointer-checking-user-defined'; new variable `ValidatePointerPtr' (fjf1052*.pas, pcerrorc.pas) (these options are _off_ by default!) * new options `--[no]-implicit-result' (fjf1022*.pas) (on by default *only* in `--delphi' mode!) (D) (@) * new options `--{en,dis}able-predefined-identifier' (fjf1037*.pas) - Bug fixes: * check initializers of unused types (fjf898*.pas) * check identifier scopes stricter (az25.pas, fjf1059*.pas) * in `--borland-pascal' give only a warning, not an error, for duplicate `case' elements (drf6*.pas) * multi-dimensional `packed' arrays are not correctly packed (fjf149*.pas) * check arithmetical overflow in constants somewhat better (fjf206*.pas) * check duplicate external declarations stricter (fjf948.pas) * check that actual discriminants match in parameters and assignments, and in strict EP mode, check that actual discriminants of parameters within one identifier list match (berend4.pas, fjf104[45]*.pas, typeof[2-4].pas) * check pointer to schema types stricter (fjf130.pas, fjf614.pas, schema3a.pas affected) * allow importing the same value as a result of distinct expressions under the same name for EP modules for ordinal, pointer, string and set constants (fjf1040*.pas, stef1.pas) * allow attributes for procedural types (chief56.pas) * problem with string operations and `goto' (contour0.pas, contourbug.pas, martin1.pas, berend3.pas) * check `goto' targets more strictly <261020020000077022%gpaeper(a)empirenet.com>, <Pine.LNX.4.44.0210281004000.31943-100000(a)duch.mimuw.edu.pl> (az48.pas, fjf701*.pas, fjf1038*.pas, gale6.pas) * `Result' is not completely Delphi compatible (fjf1022*.pas) * problem if a `Write' or `WriteLn' argument calls a routine which writes to the same file (fjf1036.pas) * `Update' as well as writing after reading or checking `EOF' can get the file position wrong in some cases (arp2*.pas, fjf159.pas, fjf160*.pas) Frank -- Frank Heckenbach, frank(a)g-n-u.de, http://fjf.gnu.de/, 7977168E GPC To-Do list, latest features, fixed bugs: http://www.gnu-pascal.de/todo.html GPC download signing key: ACB3 79B2 7EB2 B7A7 EFDE D101 CD02 4C9D 0FE0 E5E8

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better framebuffer upload
by Rick Engebretson 26 Apr '05

26 Apr '05

I just uploaded a better formatting of the framebuffer draw stuff. http://www.pinenet.com/~eng/fbDraw.html Same code as before. Just better formatting. It should work. It probably has some debug stuff still in it. Certainly not done.

1 0

Portability issues
by Rick Engebretson 26 Apr '05

26 Apr '05

Maintaining a broadly portable compiler is no easy task. But it seems clear that the Unix-like OSs are the future. Today I took time to read up on signals, IPC, terminals (ie; any serial character device). Of course all the system calls are unreadable C. Readable Object Pascal on a powerful Unix desktop. For a guy who started by feeding punched cards with fortran; wow. Great progress. Thanks.

1 0

curses and graphics window
by Anonymous 23 Apr '05

23 Apr '05

I want to move beyond my TurboPascal program in DOS. Can I keep my character based menu (very fast, compact, and efficient with screen space) for the interface, and open a graphics window for the data graphing? KDE with Qt are daunting, while Curses is appealing. Thanks.

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