Gpc September 1996

gpc@gnu.de

12 participants
49 discussions

External, C, AsmName, ...
by Peter Gerwinski 08 Sep '96

08 Sep '96

Hello folks, (* This mail is somehow long. In short: I want to take the directives `Extern', `C', and `AsmName' *out* of GPC and extend the syntax of `External' instead. Okay? :*) as you know (?;-), we have the directives `External', `Extern' (same as `External'), `C', and `AsmName' in GPC for specifying external procedures. This is especially useful when using libraries written in C, for example: Procedure Foo; External; (* yields "Foo" *) Procedure ioCtl ( FilDes, Cmd: Integer; ... ); C; (* yields "ioctl" *) Procedure XOpenDisplay ( Name: __CString__ ); AsmName 'XOpenDisplay'; This turned out not to be enough; we need the same for variables. Actually we already have Var Foo: __external__ Integer; (* yields "foo", not "Foo"! *) but this does not cover cases where the external variable needs a name with a capital letter. As an intermediate solution, I implemented Var Foo: __asmname__ 'foO' Integer; (patched source is available on demand), but I think it is not the best way to implement these things. Now I am looking out for reasonable ideas. Does somebody know what the ISO/ANSI Standards say about this? My own thoughts follow. I would suggest to define as few directives as possible and to drop everything but `External' but extend its syntax to meet our requirements. A first approach could be Procedure foo; external; (* yields "Foo" *) Var x: Integer; external; (* yields "X" *) and Procedure foo; external 'foO'; Var x: Integer; external 'my_x'; but it would crash with Borland Pascal's use of `External' where the latter declaration would mean that Procedure foo is contained in a shared library named `foO'. Okay, so let's stay for the moment at Borland's syntax. In the same context they also define Procedure foo; external 'MySharedLib' index 42; and Procedure foo; external 'MySharedLib' name 'foO'; where `foO' would be the external name as defined in the shared library. My current idea now would be to define Procedure foo; external; (* yields "Foo" *) Var x: Integer; external; (* yields "X" *) plus Procedure foo; external name 'foO'; Var x: Integer; external name 'my_x'; to replace "AsmName 'foO'". Later we can extend this to allow a name of a shared library between `external' and `name'. Once doing this, it could also be nice to make directives out of the other C-style storage qualifiers, too. I mean I'd like to replace Var x: __static__ Integer; by x: Integer; static; y: __volatile__ Integer; by y: Integer; volatile; etc.. My plan is to do it in a way that things like Var static: Integer; would still work. I think it would *not* be a good idea to make Procedure foO; external; yield "foO", because (i) it would be difficult to implement and (ii) Pascal is a case-insensitive language, so everything outside string constants *must not* depend on casing at all. Please tell me your opinion about this. Yours, Peter e-mail: peter.gerwinski(a)uni-essen.de home address: D\"usseldorfer Str. 35, 45145 Essen, Germany WWW: http://agnes.dida.physik.uni-essen.de/~peter

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gpc for Solaris 2.5.1
by brad＠shiloh.nimh.nih.gov 08 Sep '96

08 Sep '96

Hi, Is there a version of gpc built for Solaris 2.5? Or do you have any hints on getting the lastest source to compile under Solaris 2.5? Thanks Brad Zoltick NIH Email: brad(a)codon.nih.gov

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Re: Compilation error
by Peter Gerwinski 08 Sep '96

08 Sep '96

> When I try to compile anything, even the simplest program, I get: > /usr/i486-linux/bin/ld: cannot open crt0.o: No such file or directory Perhaps the versions of GCC and GPC you are using don't coincide. Please check the following: gpc -c myprogram.pas gcc myprogram.o -o myprogram i.e. compile with GPC, but link with GCC. Did you already check that crt0.o is in a directory where GPC can find it? I remember some problems when I had crt0.o in the directory /usr/lib/gcc-lib/i486-unknown-linux/2.6.3. The problems disappeared when I moved the file to /usr/lib or /usr/local/lib. Good luck, Peter e-mail: peter.gerwinski(a)uni-essen.de home address: D\"usseldorfer Str. 35, 45145 Essen, Germany WWW: http://agnes.dida.physik.uni-essen.de/~peter/

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Re: External, C, AsmName, ...
by Peter Gerwinski 08 Sep '96

08 Sep '96

According to Berend de Boer: > Can we not simply see a C .h file as an interface-only module? I mean I can > simply import a c .h file which gpc parses and all symbols defined in that > header file are exported symbols? This would mean that GPC would have to parse C source. Remember that #include "foo.h" or (*$include "foo.h" *) just means that GPC treads the file `foo.h' just if its contents were written in our source file. A Pascal program using this mechanism would in fact look like the following: Program Test; extern int foo; extern void ioctl (int fildes, int cmd, ...); begin [...] end. You don't actually want this. ;-) > I don't know how far this is feasible. And it doesn't cover a.out modules > creating using other languages (GNAT, ...). But it does cover the majority of > cases you need externals. You can write a C header file for everything you want to import, independently of the language it was originally written in. Our point is that it must also be possible to write a *Pascal* interface for everything we want to import. Peter e-mail: peter.gerwinski(a)uni-essen.de home address: D\"usseldorfer Str. 35, 45145 Essen, Germany WWW: http://agnes.dida.physik.uni-essen.de/~peter

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Re: External, C, AsmName, ...
by Berend de Boer 07 Sep '96

07 Sep '96

> Now I am looking out for reasonable ideas. Can we not simply see a C .h file as an interface-only module? I mean I can simply import a c .h file which gpc parses and all symbols defined in that header file are exported symbols? I don't know how far this is feasible. And it doesn't cover a.out modules creating using other languages (GNAT, ...). But it does cover the majority of cases you need externals. Groetjes, Berend.

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Accessing external functions (was: Newbie question)
by Peter Gerwinski 06 Sep '96

06 Sep '96

Hello Patricio, > I currently teaching Operative System to students who only know Pascal, > so I'd like to know if we can use > Unix System calls in pascal programs wirh GPC ? I mean stuff like > 'fork()', 'exec()', etc... You can access any function using the "external", "C", and "asmname" directives: Procedure fork; external; means: there is an external Procedure "Fork" (first letter uppercase), Procedure fork; C; means: there is an external Procedure "fork" (everything lowercase), and Procedure fork; asmname 'foO'; means: there is an external Procedure with the funny name "foO" (last letter is uppercase in this example) which can be accessed from Pascal via the name "fork". Good luck, Peter

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Newbie question
by Patricio Domingues 06 Sep '96

06 Sep '96

Hi, I currently teaching Operative System to students who only know Pascal, so I'd like to know if we can use Unix System calls in pascal programs wirh GPC ? I mean stuff like 'fork()', 'exec()', etc... Thanks in advance, Patricio.

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Subscribe GPC's mail list
by Patricio Domingues 06 Sep '96

06 Sep '96

Thanks.

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Compilation error
by John Michael Black 03 Sep '96

03 Sep '96

Hi all. I've had this error ever since I installed gpc, and I've never figured out why. I'm not all that experienced at unix. When I try to compile anything, even the simplest program, I get: /usr/i486-linux/bin/ld: cannot open crt0.o: No such file or directory Sorry if this seems like such a stupid question. Any ideas? -john

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Gpc September 1996