November 2006 - Gpc

Inefficiency of `mod'
by Emil Jerabek 26 Oct '10

26 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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New (gpc-20060325)
by Waldek Hebisch 08 Dec '09

08 Dec '09

I have put a new gpc snapshot at: http://www.math.uni.wroc.pl/~hebisch/gpc-20060325.tar.bz2 Main change is preliminary gcc-4.0.x support. The other changes are rather small. Note that for "production use" 3.4.x and 3.3.x backend are prefered. Also, using 2.8.1, 2.95.3 and 3.2.3 backend should work, but is depreciated. For more detail see: http://www.math.uni.wroc.pl/~hebisch/gpc/NEWS-20060325 and http://www.math.uni.wroc.pl/~hebisch/gpc/Fixed-20060325 -- Waldek Hebisch hebisch(a)math.uni.wroc.pl

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compiling static library + gpc runtime without _statvfs on Mac OS X for Intel
by Glenn Howes 20 Apr '08

20 Apr '08

Hello, After months of being distracted by another portion of my application, I'm back to creating a universal binary version of the Pascal based library we are linking into our C++ based application. The problem is the application will not launch under PPC on Mac OS X 10.3 (Panther). The console registers an undefined symbol: _statvfs expected to be defined in /usr/lib/libSystem.B.dylib After some research, I found this call is being used by the StatFS routine implemented in rts.c (line 1510) /** Get information about a file system. */ GLOBAL (Boolean _p_StatFS (char *Path UNUSED, StatFSBuffer *Buf)) { int Result; #ifdef HAVE_STATVFS struct statvfs b; errno = 0; Result = statvfs (Path, &b); Buf->BlockSize = (long long int) b.f_frsize; Buf->BlocksTotal = (long long int) b.f_blocks; Buf->BlocksFree = (long long int) b.f_bavail; Buf->FilesTotal = (int) b.f_files; Buf->FilesFree = (int) b.f_favail; #elif defined (HAVE_STATFS) struct statfs b; errno = 0; Result = statfs (Path, &b); Buf->BlockSize = (long long int) b.f_bsize; Buf->BlocksTotal = (long long int) b.f_blocks; Buf->BlocksFree = (long long int) b.f_bavail; Buf->FilesTotal = (int) b.f_files; Buf->FilesFree = (int) b.f_ffree; #else Result = -1; errno = ENOSYS; #endif if (Result == 0) return True; Buf->BlockSize = 0; Buf->BlocksTotal = 0; Buf->BlocksFree = 0; Buf->FilesTotal = 0; Buf->FilesFree = 0; return False; } It appears to me that HAVE_STATVFS is defined if my current OS X SDK (10.4) has a statvfs.h header file amongst its include files, which means if I build my Pascal development environment from the build-on- Intel.command that the statvfs version will be hard wired into the runtime and any binary I generate will not work on 10.3 (which does not have statvfs in its libSystem.B.dylib library). Also, if I build my environment/library on a PowerPC using the build-on- powerPC-10.3.command, I end up with a different set of link problems involving the long double version of pow(). Besides which, I'd prefer to do my development on OS X for Intel going forward. I have tried hand editing the above routine and rebuilding my Pascal development environment, and pulling the statvfs.h file from my OS X SDK, and yet when my application links, it still has an unresolved reference to _statvfs. I'm not a build engineer, as my previous missives to this mailing list make clear, and I'm at a loss as to how to proceed. Just to be clear, I link in two static libraries: a universal version of the libgpc.a for the runtime, and a universal version of the library I've created. Neither of them contain the symbol _statvfs (at least I can't find that text in them). I link that with my application. The application now references _statvfs (I can now see the text in it's executable). I can't launch on 10.3. I comment out the calls to the Pascal library and recompile+relink, and the application no longer has the symbol and I can launch under 10.3. So something in either of the gpc associated libraries must be calling something which calls statvfs, making the linker (ld) mark statvfs as an unresolved symbol to be loaded in at runtime. At least that is my impression. So, I'd appreciate some suggestions. --glenn

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Memory layout of array of variable size.
by Bastiaan Veelo 24 Dec '07

24 Dec '07

Hi, In an attempt to hook up to GTK+, I am trying to pass a Pascal array of varible size to C. Static arrays are fine, but these arrays carry some additional information like capacity and size, and I gues they could be received as a struct on the C-side. However, I cannot figure out the structure that the struc should have. I do like this in Pascal: procedure YGTK_init(var argc : CInteger; argv : array of CString); external name 'YGTK_init'; procedure Y_init; var argc : CInteger; argv : array[0..ParamCount] of CString; Counter : integer; begin argc := ParamCount+1; for Counter := 0 to ParamCount do begin argv[Counter] := NewCString(ParamStr(Counter)); end; YGTK_init(argc, argv); end; And like this in C: struct t_argv { int end; void *argv; }; void YGTK_init( int *argc, struct t_argv argv ) { printf("In ygtk.c:YGTK_init.\n"); printf("argv.end: %d\n", argv2.argc); printf("argv.argv address: %p\n", argv2.argv); printf("argv.argv int: %d\n", argv2.argv); printf("argv.argv string: %s\n", argv2.argv); printf("number of arguments: %d\n", *argc); } So I figured out that the first element in the struct is an integer containing the length-1 of the array, but what it should look like for the rest I do not know yet. Do you have an idea? Thanks, Bastiaan.

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Bug: copy
by Andreas K. Foerster 28 Nov '06

28 Nov '06

Hello, I came across a strange thing in gpc. My programs compile well with old versions of gpc, but when someone tried to compile the program with his version, it broke. It made me look very bad. :-( The function "copy" doesn't seem to accept the result of a function anymore. I consider that as a bug. --------------------------------------------------------------- program akf1; uses GPC; function mytext: TString; begin mytext := 'something ...' end; begin WriteLn(copy(mytext, 1, 9)) end. --------------------------------------------------------------- -- AKFoerster

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break bug report
by Russ Whitaker 26 Nov '06

26 Nov '06

Hi Got careless and used "break" where I should use "exit" and got this: try.pas: In main program: try.pas:7: internal compiler error: in plant_exit_loop, at p/plant.c:651 Please submit a full bug report, with preprocessed source if appropriate. See <URL:http://www.gnu-pascal.de/todo.html> for instructions. from this: program bug; uses gpc; begin if FileExists( Paramstr( ParamCount ) ) then begin writeln('Quitting: output file "', Paramstr( ParamCount ), '" exists'); break; end; end. gpc version 20060325, based on gcc-4.1.1 Russ

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more on gp
by Frank McCormick 16 Nov '06

16 Nov '06

On Tue, 14 Nov 2006 22:58:17 +0100 Frank Heckenbach <ih8mj(a)fjf.gnu.de> wrote: > > > Frank McCormick wrote: > > > > > > > gp: Pascal and C compilers specified seem to be for different > > > > platforms gp: (`i686-pc-linux-gnu' and `i486-linux-gnu') > > > > > > GP by default compares the versions of GPC and GCC very strictly to > > > avoid subtle errors that could result on mismatch. If you know the > > > mismatch is harmless (e.g., as above, just a different labeling of > > > targets), you can add "--no-check-platform" to skip this check. > > > > I tried putting --no-check-platform into a .gp config file in my > > home directory and it works...but only sometimes. Seems to depend on whether I am in an > > IDE (Anjuta/Peng/Geany) or at the cli. Does GP always check ~.gp ? > > No, GP doesn't currently read any config file itself (this is > planned in the future, though). Soon ? > This seems to be a feature of your > IDE. (Though for PENG, which I wrote, I'm not aware of such a > feature. ;-) However, PENG allows doing such things in user-defined > tools, so perhaps this was done in your setup.) > > To make it work on the command line, too, you can use the usual > means of a shell alias or a tiny wrapper script to add this option. Alias seems to work well. Thanks -- Cheers Frank

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Works sometimes.
by fmccormick＠videotron.ca 14 Nov '06

14 Nov '06

On Sun, 12 Nov 2006 19:23:21 +0100 Frank Heckenbach <ih8mj(a)fjf.gnu.de> wrote: > Frank McCormick wrote: > > > > > gp: Pascal and C compilers specified seem to be for different > > platforms gp: (`i686-pc-linux-gnu' and `i486-linux-gnu') > > > > GP by default compares the versions of GPC and GCC very strictly to > avoid subtle errors that could result on mismatch. If you know the > mismatch is harmless (e.g., as above, just a different labeling of > targets), you can add "--no-check-platform" to skip this check. I tried putting --no-check-platform into a .gp config file in my home directory and it works...but only sometimes. Seems to depend on whether I am in an IDE (Anjuta/Peng/Geany) or at the cli. Does GP always check ~.gp ? ---Frank McCormick--- ------Montreal--------

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error message
by Frank McCormick 12 Nov '06

12 Nov '06

Something must have changed on my system because now I am getting this error message once in a while: gp: Pascal and C compilers specified seem to be for different platforms gp: (`i686-pc-linux-gnu' and `i486-linux-gnu') I usually happens when I use gp instead of gpc. Any ideas ? Thanks

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GPC is falling out of the mainstream
by CBFalconer 08 Nov '06

08 Nov '06

GPC is falling out of the mainstream, due to the failure to integrate it with gcc. It seems to me this should take priority. -- Chuck F (cbfalconer at maineline dot net) Available for consulting/temporary embedded and systems. <http://cbfalconer.home.att.net>

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