December 2009 - 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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GPC support for AIX 6?
by Gert Doering 16 Feb '10

16 Feb '10

Hi Gnu Pascal list, we're currently using IBM's xpc pascal compiler on IBM AIX 5.3. New machines are being shipped with AIX 6, and IBM's xpc is no longer supported there - for the time being, it actuall works (the xpc frontend generated intermediate code, and the second stage compiler still groks it). Management is not happy about this, as it might break any day, and I have been asked to "provide GPC" on AIX 6. Googling seems to suggest that the earliest release of GCC to work on AIX 6 is gcc 4.2.4 This mailing list's archive suggests that GPC and GCC 4.2 do not yet work together, due to larger efforts required due to backend changes (Waldek's mail from March 12, 2008). I reported this to management ("there is no GPC on AIX 6"), and they came back with the question "if we pay one of the GPC developers to do a GPC port to a recent GCC, to support AIX 6, how much would that cost?". Here we go - I'm posing this question to you. Is one of you capable and willing to make GPC work on AIX 6? And if yes, what would your conditions be (estimated time to do this, estimated costs)? (I can't promise anything, but will report back to management and they will decide...) thanks, gert -- Gert Doering gd(a)medat.de MEDAT Muenchen Tel: 089/126808-0 Fax: -50

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Unable to print
by Contestcen＠aol.com 21 Dec '09

21 Dec '09

I tried that statement, but it did not recognize the command "net". Also the Pascal program seems to bomb when I use any value other than 'USB001' in the call to InitPrinter (or when I omit InitPrinter). The printer is connected directly to my computer by a USB cable. There is no local net. Date: Thurs, Dec 17 2009 5:00 am From: "Zaphod Beeblebrox" "SirJohn" <contestcen(a)aol.com> wrote in message news:dff19abd-9e4d-40c0-a4cb-d7aa8b66e7a3@j14g2000yqm.googlegroups.com... >I just moved to Windows 7, which means that I now connect to my > printer via a USB port instead of a serial port. In those FPC > programs which use the printer I changed InitPrinter('LPT1') to > InitPrinter('USB001') however, everything I print is now going to a > disk file named USB001 instead of to the printer. What else do I > need > to get this working? Make sure the printer is shared, and then use the following command to redirect LPT2 to the printer: net use LPT2: \\computername\printername /persistent:yes Replace 'computername' with your computer name, and 'printername' with the share name of your printer. After you've run the command, you should be able to use InitPrinter('LPT2') in your program. BTW, you want to use LPT2 since from what I've read, if the printer port actually exists, Vista and Windows 7 won't let you redirect to it. Hope this helps.

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Unable to print
by Contestcen＠aol.com 21 Dec '09

21 Dec '09

I am using FPC 2.2.4 for i386. From: Marco van de Voort On 2009-12-17, SirJohn <contestcen(a)aol.com> wrote: > I just moved to Windows 7, which means that I now connect to my > printer via a USB port instead of a serial port. In those FPC > programs which use the printer I changed InitPrinter('LPT1') to > InitPrinter('USB001') however, everything I print is now going to a > disk file named USB001 instead of to the printer. What else do I need > to get this working? Which FPC are you using on windows 7? Could be one of the following three editions: go32v2/win32/win64 ? Note that go32v2(dos) is not supported/recommended on NT based windowses (NT4/2k/2k3/xp/vista/w2k8/w7).

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Compiler differences
by John Gordon Ollason 11 Dec '09

11 Dec '09

Greetings, Having installed gpc 20060325, based on gcc-3.4.4 in replacement of gpc 20041218, based on gcc-3.3.3 I discovered that some programs which worked on the earlier version don't work on the later one. I narrowed the problem down to changes in the behaviour of goto. program gototest; label 9999; procedure try; begin goto 9999; end; { try } begin try; 9999: end. The program gototest.p is compiled by both compilers. The following program gototest1; label 9999; procedure try; begin goto 9999; end; { try } begin repeat try; 9999: until 0=0; end. is compiled by gpc 20041218 but the newer compiler gives the following error: gpc --classic-pascal gototest.p gototest.p: In main program: gototest.p:10: error: invalid target for nonlocal `goto' I have had a look at the ISO7185 specification, and though I am not an expert in these matters, it seems to me that the newer compiler is behaving incorrectly. Incidentally FreePascal gives the following error for both programs: Free Pascal Compiler version 2.2.2 [2008/10/26] for x86_64 Copyright (c) 1993-2008 by Florian Klaempfl Target OS: Linux for x86-64 Compiling gototest.p gototest.p(5,13) Error: Goto statements aren't allowed between different procedures gototest.p(14) Fatal: There were 1 errors compiling module, stopping Fatal: Compilation aborted Error: /usr/bin/ppcx64 returned an error exitcode (normal if you did not specify a source file to be compiled) Are any of the compilers behaving as specified in the ISO7815 standard? Best wishes, John O.

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Compiling and linking Gnu-Pascal under Fedora 11 on x86_64 hardware.
by John Gordon Ollason 09 Dec '09

09 Dec '09

Greetings, I had to upgrade my hardware from i686 to x86_64 and my operating system from Fedora Core 4 to Fedora Core 11. I have tried to install Gnu-Pascal by downloading several versions from the Gnu-Pascal homepage and all attempts fail Every attempt to use make terminated in errors as follows: -- . . . make[2]: *** [32/libgcc_s_32.so] Error 1 make[2]: Leaving directory `/usr/local/src/gpcbuild/gcc' make[1]: *** [libgcc.a] Error 2 make[1]: Leaving directory `/usr/local/src/gpcbuild/gcc' make: *** [all-gcc] Error 2 fail. -- I downloaded the install.gpc script and that didn't work either. The closest I have got to a working system is illustrated by the listing below. -- $ gpc -v hello.p Using built-in specs. Configured with: ../gcc-3.4.4/configure --enable-languages=pascal : (reconfigured) ../gcc-3.4.4/configure --enable-languages=pascal : (reconfigured) ../gcc-3.4.4/configure --enable-languages=pascal : (reconfigured) ../gcc-3.4.4/configure --enable-languages=pascal Thread model: posix gpc version 20070904, based on gcc-3.4.4 gpc1 -quiet -v hello.p -quiet -dumpbase hello.p -mtune=k8 -famtmpfile=/tmp/cceErexo.gpa -version -o /tmp/ccsxBXZC.s GNU Pascal version 20070904, based on gcc-3.4.3 (x86_64-unknown-linux-gnu) compiled by GNU C version 4.4.1 20090725 (Red Hat 4.4.1-2). GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072 GNU Pascal Compiler PreProcessor version 20070904, based on gcc-3.4.3 as -V -Qy -o /tmp/ccUtT5MU.o /tmp/ccsxBXZC.s GNU assembler version 2.19.51.0.14 (x86_64-redhat-linux) using BFD version version 2.19.51.0.14-1.fc11 20090722 ld --eh-frame-hdr -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 /usr/lib/../lib64/crt1.o /usr/lib/../lib64/crti.o /usr/lib/../lib64/crtbegin.o -L/usr/local/lib/gcc/x86_64-unknown-linux-gnu/3.4.4 -L/usr/local/lib/gcc/x86_64-unknown-linux-gnu/3.4.4/../../../../lib64 -L/usr/local/lib/gcc/x86_64-unknown-linux-gnu/3.4.4/../../.. -L/lib/../lib64 -L/usr/lib/../lib64 /tmp/ccUtT5MU.o -lgpc -lm -lgcc -lc -lgcc crtend.o /usr/lib/../lib64/crtn.o ld: cannot find -lgpc -- and there I am stuck. Any constructive suggestions about what to try next would be very welcome. Thanks, John O.

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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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