Portable C code

Discussion in 'C Programming' started by Kristan Dyson, Oct 5, 2006.

  1. I was just wondering whether you knew whether it is possible to compile a
    fully portable C program? I want to write a 'C' CGI program on Windows,
    then just upload it to my Plus.Net Debian-based server.
    As I want to write pure ANSI C, then I thought it may be possible to write a
    program that would run fine on both. Having said that, surely (?), it would
    have to be compiled for specific platforms, unless of course there is some
    abstraction layer at runtime, like with java. Anyway, this is probably not
    possible now I have thought about it.


    But I would love to know what you guys and gals think?!



    Cheers,

    Kristan
    Kristan Dyson, Oct 5, 2006
    #1
    1. Advertising

  2. >I was just wondering whether you knew whether it is possible to compile a
    >fully portable C program? I want to write a 'C' CGI program on Windows,
    >then just upload it to my Plus.Net Debian-based server.


    Source code is portable. Executables are not. It is quite possible
    that an executable on one OS is not recognized as an executable on
    another, even if they are running on the actual same CPU (which
    dual-boots different OSs). And even if it is, it may not run correctly.

    >As I want to write pure ANSI C, then I thought it may be possible to write a
    >program that would run fine on both.


    Compile it on both.

    >Having said that, surely (?), it would
    >have to be compiled for specific platforms, unless of course there is some
    >abstraction layer at runtime, like with java. Anyway, this is probably not
    >possible now I have thought about it.
    >
    >
    >But I would love to know what you guys and gals think?!
    Gordon Burditt, Oct 5, 2006
    #2
    1. Advertising

  3. [Followups set to comp.lang.c, since I don't suppose the Microsoft people
    are all that interested in portability]

    Kristan Dyson said:

    > I was just wondering whether you knew whether it is possible to compile a
    > fully portable C program?


    That depends on what you mean by "fully portable", of course. But it's
    certainly possible to have a very, very portable C program.

    What is not possible, alas, is to have one binary that runs on any platform
    you like - no matter what language it's written in.

    So you do need a compiler on each platform (or group of binary-compatible
    platforms) that you wish to support.

    > I want to write a 'C' CGI program on Windows,
    > then just upload it to my Plus.Net Debian-based server.
    > As I want to write pure ANSI C, then I thought it may be possible to write
    > a program that would run fine on both.


    Well, the point of writing it in pure ANSI C is so that you can compile the
    source code without first having to customise it to a particular platform.

    --
    Richard Heathfield
    "Usenet is a strange place" - dmr 29/7/1999
    http://www.cpax.org.uk
    email: rjh at above domain (but drop the www, obviously)
    Richard Heathfield, Oct 5, 2006
    #3
  4. Kristan Dyson wrote:
    > I was just wondering whether you knew whether it is possible to compile a
    > fully portable C program? I want to write a 'C' CGI program on Windows,
    > then just upload it to my Plus.Net Debian-based server.
    > As I want to write pure ANSI C, then I thought it may be possible to write a
    > program that would run fine on both. Having said that, surely (?), it would
    > have to be compiled for specific platforms, unless of course there is some
    > abstraction layer at runtime, like with java. Anyway, this is probably not
    > possible now I have thought about it.

    It depends on what the CGI program must do.
    If it can accomplish its goal by standard C, go for it.
    CGI programs typically only reads from stdin, writes
    to stdout which surly can be done in standard C.
    Care must be taken on how you handle and convert
    input/output data though.

    If you need other features - sockets, database access, etc.
    it is not, but perhaps you can find third party packages for
    such things that atleast are portable among the systems you
    want to support.
    =?ISO-8859-1?Q?=22Nils_O=2E_Sel=E5sdal=22?=, Oct 5, 2006
    #4
  5. "Richard Heathfield" <> wrote in message
    news:...
    > [Followups set to comp.lang.c, since I don't suppose the Microsoft people
    > are all that interested in portability]

    snip
    There is nothing quite as stationary as an island, e.g. England. It is c
    that doesn't talk to MS, not the other way around. EC
    Elijah Cardon, Oct 5, 2006
    #5
  6. Kristan Dyson

    Chris Dollin Guest

    Elijah Cardon wrote:

    > "Richard Heathfield" <> wrote in message
    > news:...
    >> [Followups set to comp.lang.c, since I don't suppose the Microsoft people
    >> are all that interested in portability]

    > snip
    > There is nothing quite as stationary as an island, e.g. England.


    Eh?

    > It is c that doesn't talk to MS, not the other way around. EC


    C doesn't talk /at all/. Neither does it eat, or write three-volume
    novels, nor snore at twenty-seven minutes past three in the morning.

    Unpack?

    --
    Chris "falling further in" Dollin
    "No-one here is exactly what he appears." G'kar, /Babylon 5/
    Chris Dollin, Oct 5, 2006
    #6
  7. Kristan Dyson

    Kristan Guest

    Thank you all for your help! Hopefully, I will one day know enough about C
    / C++ to return the favour

    cheers
    kristan

    "Kristan Dyson" <> wrote in message
    news:4524efa1$0$24467$...
    >I was just wondering whether you knew whether it is possible to compile a
    >fully portable C program? I want to write a 'C' CGI program on Windows,
    >then just upload it to my Plus.Net Debian-based server.
    > As I want to write pure ANSI C, then I thought it may be possible to write
    > a program that would run fine on both. Having said that, surely (?), it
    > would have to be compiled for specific platforms, unless of course there
    > is some abstraction layer at runtime, like with java. Anyway, this is
    > probably not possible now I have thought about it.
    >
    >
    > But I would love to know what you guys and gals think?!
    >
    >
    >
    > Cheers,
    >
    > Kristan
    >
    >
    Kristan, Oct 5, 2006
    #7
  8. Kristan Dyson

    John Smith Guest

    Kristan Dyson wrote:

    > I was just wondering whether you knew whether it is possible to compile a
    > fully portable C program? I want to write a 'C' CGI program on Windows,
    > then just upload it to my Plus.Net Debian-based server.


    You would need to upload the source code and then recompile on the
    server to generate new binary executables. If don't have shell access,
    or if there is no compiler on the server, you may be screwed.

    That's probably one of the things that makes an interpreted language
    like Perl more popular for CGI stuff. Install a Windows version of Perl
    (ActivePerl ??), monkey with your scripts until they work, then just put
    them in proper place on the server.
    John Smith, Oct 5, 2006
    #8
  9. Kristan Dyson

    quarkLore Guest

    John Smith wrote:
    > Kristan Dyson wrote:
    >
    > > I was just wondering whether you knew whether it is possible to compile a
    > > fully portable C program? I want to write a 'C' CGI program on Windows,
    > > then just upload it to my Plus.Net Debian-based server.

    >

    I don't know much about that
    > You would need to upload the source code and then recompile on the
    > server to generate new binary executables. If don't have shell access,
    > or if there is no compiler on the server, you may be screwed.
    >

    People have told, make the source code portable, binaries are not
    portable.

    > That's probably one of the things that makes an interpreted language
    > like Perl more popular for CGI stuff. Install a Windows version of Perl
    > (ActivePerl ??), monkey with your scripts until they work, then just put
    > them in proper place on the server.

    Perl is good for CGI. So decide early to go for perl/script type
    thingies or a full fledged programming language like C.

    How to make portable code in C:

    1. Have an indepth knowledge of features in ANSI-C. (Not just internals
    in C)
    2. Study the compilers on platforms you are working in. Different
    compilers may or may not support all the features of ANSI-C
    3. Try not to use dirty hacks, though great, they are often device
    specific
    4. Then the lame stuff: design your program logic independent of OS. So
    divide device/platform specific code to the logical part of it. e.g.
    Don't directly assume fopen would be available created a wrapper for
    it.

    These are just starters if you are new to making code portable.
    quarkLore, Oct 6, 2006
    #9
  10. In article <c4dVg.3188$>,
    John Smith <> wrote:
    >Kristan Dyson wrote:


    >> I was just wondering whether you knew whether it is possible to compile a
    >> fully portable C program? I want to write a 'C' CGI program on Windows,
    >> then just upload it to my Plus.Net Debian-based server.


    >You would need to upload the source code and then recompile on the
    >server to generate new binary executables. If don't have shell access,
    >or if there is no compiler on the server, you may be screwed.


    There are cross-compilers available in limited cases.


    >That's probably one of the things that makes an interpreted language
    >like Perl more popular for CGI stuff. Install a Windows version of Perl
    >(ActivePerl ??), monkey with your scripts until they work, then just put
    >them in proper place on the server.


    No, Perl turns out to relatively *not* portable. For more words
    on this subject, please see my earlier posting,
    http://groups.google.ca/group/comp.lang.c/msg/044fa97697731535
    --
    Okay, buzzwords only. Two syllables, tops. -- Laurie Anderson
    Walter Roberson, Oct 6, 2006
    #10
  11. Kristan Dyson

    John Smith Guest

    Kristan Dyson wrote:
    > I was just wondering whether you knew whether it is possible to compile a
    > fully portable C program? I want to write a 'C' CGI program on Windows,
    > then just upload it to my Plus.Net Debian-based server.
    > As I want to write pure ANSI C, then I thought it may be possible to write a
    > program that would run fine on both. Having said that, surely (?), it would
    > have to be compiled for specific platforms, unless of course there is some
    > abstraction layer at runtime, like with java. Anyway, this is probably not
    > possible now I have thought about it.
    >
    >
    > But I would love to know what you guys and gals think?!
    >
    >
    >
    > Cheers,
    >
    > Kristan
    >
    >

    /* Stirling's approximation for n! & ln(n!) */
    #include <stdio.h>
    #include <stdlib.h>
    #include <math.h>
    #define PI 3.141592653589793
    long double stirling(long double n);
    long double lnstirling(long double n);

    int main(int argc, char *argv[])
    {
    long double n, sa, lnsa, pi;

    if(argc != 2) exit(EXIT_FAILURE);
    pi = PI;
    n = strtold(argv[1], NULL);
    sa = stirling(n);
    lnsa = lnstirling(n);
    printf("%.Lf! = %.2Lf\n", n, sa);
    printf("ln(%.Lf!) = %.8Lf\n", n, lnsa);

    return 0;
    }

    /* Stirling's approximation */
    long double stirling(long double n)
    {
    long double t1, t2, t3;

    t1 = sqrt(2.0 * PI * n);
    t2 = pow(n, n);
    t3 = exp(-n + 1.0 / 12.0 / n);

    return t1 * t2 * t3;
    }

    /* ln(stirling) */
    long double lnstirling(long double n)
    {
    return (n +.5) * log(n) - n + log(2.0 * PI) / 2.0;
    }

    *** not part of the program above for Sterlings approximation **

    /* Return the natural log of gamma(x) */
    double log_gamma(double x)
    {
    int idx, sizep;
    double r, g;
    double p[] = {1.000000000190015,
    76.18009172947146,
    -86.50532032941677,
    24.01409824083091,
    -1.231739572450155,
    1.208650973866179E-3,
    -5.395239384953E-6};
    r = p[0];
    g = 5.;
    sizep = sizeof(p) / sizeof(*p);

    for (idx = 1; idx < sizep; idx++)
    {
    r += p[idx] / (x + idx);
    }

    return log(r) + log(atan(1) * 8) / 2 - log(x) +
    log(x + g + .5) * (x + .5) - (x + g + .5);
    }
    John Smith, Oct 7, 2006
    #11
  12. "quarkLore" <> wrote in message
    news:...
    > 4. Then the lame stuff: design your program logic independent of OS. So
    > divide device/platform specific code to the logical part of it. e.g.
    > Don't directly assume fopen would be available created a wrapper for
    > it.

    Good point (and very smart design), however do you really think that fopen
    should be included in this category? I mean isn't fopen() a part of the C
    standard? So it should be in the implementation of every C compiler

    --
    Abdo Haji-Ali
    Programmer
    In|Framez
    Abdo Haji-Ali, Oct 7, 2006
    #12
  13. fopen (standard library) is part of conforming virtual machine. Standard C
    allows non-conforming environment, too. Filename format is also
    platform-dependent.

    "Abdo Haji-Ali" <_use_com_instead> wrote in message
    news:...
    > "quarkLore" <> wrote in message
    > news:...
    >> 4. Then the lame stuff: design your program logic independent of OS. So
    >> divide device/platform specific code to the logical part of it. e.g.
    >> Don't directly assume fopen would be available created a wrapper for
    >> it.

    > Good point (and very smart design), however do you really think that fopen
    > should be included in this category? I mean isn't fopen() a part of the C
    > standard? So it should be in the implementation of every C compiler
    >
    > --
    > Abdo Haji-Ali
    > Programmer
    > In|Framez
    >
    >
    Alexander Grigoriev, Oct 7, 2006
    #13
  14. "Alexander Grigoriev" <> writes:
    > "Abdo Haji-Ali" <_use_com_instead> wrote in message
    > news:...
    >> "quarkLore" <> wrote in message
    >> news:...
    >>> 4. Then the lame stuff: design your program logic independent of OS. So
    >>> divide device/platform specific code to the logical part of it. e.g.
    >>> Don't directly assume fopen would be available created a wrapper for
    >>> it.

    >> Good point (and very smart design), however do you really think that fopen
    >> should be included in this category? I mean isn't fopen() a part of the C
    >> standard? So it should be in the implementation of every C compiler
    >>

    > fopen (standard library) is part of conforming virtual
    > machine. Standard C allows non-conforming environment, too. Filename
    > format is also platform-dependent.


    Please don't top-post. Read these links:
    http://www.caliburn.nl/topposting.html
    http://www.cpax.org.uk/prg/writings/topposting.php

    Standard C doesn't "allow" non-conforming environments, except in the
    fairly obvious sense that if an environment doesn't conform to the C
    standard, the standard has nothing to say about it.

    fopen() is required for all conforming hosted implementations. It's
    not required for conforming freestanding implementations (typically
    embedded systems). But an implementation that doesn't provide fopen()
    likely doesn't have a file system at all.

    --
    Keith Thompson (The_Other_Keith) <http://www.ghoti.net/~kst>
    San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
    We must do something. This is something. Therefore, we must do this.
    Keith Thompson, Oct 7, 2006
    #14
  15. > fopen() is required for all conforming hosted implementations. It's
    > not required for conforming freestanding implementations (typically
    > embedded systems). But an implementation that doesn't provide fopen()
    > likely doesn't have a file system at all.


    ....or several of them :)
    Bertrand Augereau, Oct 9, 2006
    #15
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Eli Bendersky
    Replies:
    1
    Views:
    1,152
    Mike Treseler
    Mar 1, 2006
  2. Shin
    Replies:
    5
    Views:
    4,297
  3. The Saqe

    Looking for portable C++ code

    The Saqe, Sep 23, 2003, in forum: C++
    Replies:
    3
    Views:
    346
    Noah Roberts
    Sep 24, 2003
  4. Rolf Hemmerling
    Replies:
    3
    Views:
    747
    Roger Leigh
    Oct 31, 2003
  5. Replies:
    7
    Views:
    903
Loading...

Share This Page