make a preprocessor

This is a discussion on make a preprocessor within the C Programming forums, part of the General Programming Boards category; Hello everybody, i'm a computing student and i'm working in making a php compiler. I have to make something like ...

  1. #1
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    make a preprocessor

    Hello everybody, i'm a computing student and i'm working in making a php compiler.

    I have to make something like a preprocess to treat the #include sentences contained in the php scripts. I'm working with LEX/YACC and now i'm trying to make a function that can copy the code from a source file to another.

    Doing this, if the source file is large, i obtain a "segment violation".

    And I don't know how to append the read text instead of overwrite it...

    Code:
     #include <stdio.h>
    
    int main(int argc, char *argv[])
    {
    	FILE *fuente;
    	FILE *destino;
        fuente = fopen(argv[1], "r"); 
    	destino = fopen("prueba.php", "w");
    
    	char *linea;
    	int tam = 999;
    
        if (fuente == NULL) {
           printf("El fichero fuente no existe\n");
           return(-1);
           }
        else{ 
       while (!feof(fuente)){
    	   fgets(linea,tam,fuente);
    	   fputs(linea,destino);	
    	   printf("%s\n",linea);
       }
        
       fclose(fuente);
       fclose(destino);
    
        }   
    
    }
    I'll be very pleased if someone could give me an idea or if anybody could tell me something about preprocessing that.

    Thanks!!!

  2. #2
    CSharpener vart's Avatar
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    char *linea;
    int tam = 999;
    fgets(linea,tam,fuente);
    You are telling to fgets that the linea pointer points to the buffer able to store 999 bytes
    But actually it contains some random adress.
    so when fgets starts writing there or GPF occurs or some random memory of your process is overwritten
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  3. #3
    CSharpener vart's Avatar
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    And I don't know how to append the read text instead of overwrite it...
    You should read about file open modes... i think "a" will suite you
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  4. #4
    and the hat of wrongness Salem's Avatar
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    > while (!feof(fuente))
    And read the FAQ on why using feof() to control a loop is bad.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
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  5. #5
    Frequently Quite Prolix dwks's Avatar
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    What's to say that argv[1] isn't NULL? You should check the number of command-line parameters passed to the program. And whether or not the files could be opened.

    Also, declaring variables in the middle of a block is C99.
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
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    I'checked all your comments (thank you guys) and I think my problem actually is about the memory and what vart has written...

    How can I resolve that? Do you know about a good guide or FAQ or something similar about files in C?

    Thank you very much

  7. #7
    Cat without Hat CornedBee's Avatar
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    Why read the file in the first place? You can tell LEX to use a different source temporarily. The documentation contains a section on that.
    All the buzzt!
    CornedBee

    "There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
    - Flon's Law

  8. #8
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    Quote Originally Posted by CornedBee
    Why read the file in the first place? You can tell LEX to use a different source temporarily. The documentation contains a section on that.
    I've read this documentation and it seems too dificult and I have no much time, but it's ok, I've found a solution with a simple memory allocation.

    Thank you all, see ya

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