splint debugging parse error

Question

This is my first time using splint (from Ubuntu repositories) and I immediately got hit by a WTF. The error message:

nightcracker@nightcracker-pc:~/c/brainfuck$ splint brainfuck.c
Splint 3.1.2 --- 03 May 2009

brainfuck.c:17:6: Parse Error. (For help on parse errors, see splint -help
               parseerrors.)
*** Cannot continue.

Now, apparently it sees something wrong on line 16, column 6. Let's check that out (posting full code):

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

enum {
    CELL_CHUNK_SIZE = 1024,
};

typedef unsigned char cell;

int main(int argc, char *argv[]) {
    if (argc < 1) {
        fprintf(stderr, "ERROR: Not enough arguments\n");
        return 1;
    }

    FILE  *srcfile; // source file << THIS LINE APPARENTLY IS WRONG
    long srclen; // source file size
    char *bf; // brainfuck code file in memory

    char *ip; // instruction pointer
    cell *cells; // brainfuck cells
    cell *newcells; // used for creating a new chunk of cells
    cell *cp; // cell pointer
    unsigned long numcells = CELL_CHUNK_SIZE; // amount of current cells
    unsigned nest; // current nesting
    int buf; // i/o buffer

    srcfile = fopen(argv[1], "rb");
    if (srcfile == NULL) {
        fprintf(stderr, "ERROR: Couldn't open source file\n");
        return 2;
    }

    // get source file length
    fseek(srcfile, 0, SEEK_END);
    srclen = ftell(srcfile);
    fseek(srcfile, 0, SEEK_SET);

    // allocate memory for source file
    bf = malloc(srclen);
    if (bf == NULL) {
        fprintf(stderr, "ERROR: Couldn't allocate memory for source file\n");
        return 3;
    }

    // read source file in memory
    if (srclen != fread(bf, sizeof(char), srclen, srcfile)) {
        fprintf(stderr, "ERROR: Error while reading source file\n");
        free(bf);
        return 4;
    }

    fclose(srcfile);

    cells = malloc(CELL_CHUNK_SIZE * sizeof(cell));
    memset(cells, 0, CELL_CHUNK_SIZE);

    if (cells == NULL) {
        fprintf(stderr, "ERROR: Memory allocation failed\n");
        free(bf);
        free(cells);
        return 5;
    }

    cp = cells; // cell pointer initialized to most-left cell
    ip = bf; // instruction pointer initialized to first character
    nest = 0;

    while (ip >= bf && ip <= (bf + srclen)) {
        switch (*ip) {
            case '+':
                (*cp)++;
                break;
            case '-':
                (*cp)--;
                break;
            case '>':
                cp++;
                if ((cp - cells) == numcells) {
                    newcells = realloc(cells, (numcells + CELL_CHUNK_SIZE) * sizeof(cell)); // allocate memory for new chunk

                    if (newcells == NULL) {
                        fprintf(stderr, "ERROR: Memory allocation failed\n");
                        free(bf);
                        free(cells);
                        return 5;
                    }

                    cp = newcells + (cp - cells); // point cell pointer to cell in new chunk
                    cells = newcells; // point cells to new memory location (if altered)
                    memset(cp, 0, CELL_CHUNK_SIZE); // initialize new chunk
                    numcells += CELL_CHUNK_SIZE;
                }
                break;
            case '<':
                cp--;
                break;
            case '.':
                putchar(*cp);
                break;
            case ',':
                if ((buf = getchar()) != EOF) {
                    *cp = (unsigned char) buf;
                } else *cp = 0;
                break;
            case '[':
                if (!(*cp)) {
                    ip++; // move past the opening bracket
                    while (nest > 0 || *ip != ']') { // skip to matching ]
                        if (*ip == '[') nest++; // enter nest
                        if (*ip == ']') nest--; // leave nest (or main loop, in which nesting > 0 fails)

                        ip++; // move right
                    }

                }
                break;
            case ']':
                if (*cp) {
                    ip--; // move before the closing bracket
                    while (nest > 0 || *ip != '[') { // rewind to matching [
                        if (*ip == '[') nest--; // leave nest (or main loop, in which nesting > 0 fails)
                        if (*ip == ']') nest++; // enter nest

                        ip--; // move left
                    }
                    ip--; // move before the opening bracket
                }
                break;
        }

        ip++; // move to next instruction
    }


    free(cells);
    free(bf);
    return 0;
}

Note that this program compiles without errors (gcc -Wall -std=c99 brainfuck.c) and runtime behaves normal.

Note: if you are offended by the name brainfuck, live with it. It's a programming language that is named that way by the author and I respect and use that name.

Tamas

Answer 1

Is splint C99 aware?

Try /* ... */ instead of // ... and move declarations to before any code

Smooth

OMG I never knew single-line comments were introduced in c99. My compiler never complained, even without -std=c99. Though sadly this doesn't fix my issue. – Tamas

I've added another C99 thing to my post (declarations mixed with code is new too) – Smooth

@nightcracker: quite a few compilers accepted // as an extension, but it wasn't officially part of the language until C99. – Cagle

Is it then considered a bad practice? I find it much easier and better as it doesn't block commenting out blocks of code. – Tamas

Accepted. Moving declarations did the trick. Never knew that too >.< After googling I found this: bugs.debian.org/cgi-bin/bugreport.cgi?bug=369264 – Tamas

I think it's ok (not bad practice) to use // ... comments and declarations mixed with code. If your source is never going to see a C89 compiler (without extras) or any old-fashioned tool (like splint) you won't run into any troubles – Smooth

What would you recommend for filtering out common errors instead of splint? – Tamas

@nightcracker: I tend to write C89 so splint works for me ... but compilers are pretty good at catching common errors and silly mistakes nowadays. Crank up your compiler diagnostics. – Smooth

My compiler diagnostics are fine (-Wall). I was thinking that maybe it didn't pick up everything, but they indeed are very good these days. Hmm, maybe I shouldn't have read K&R version 1 as my first (and ATM only) C book. – Tamas

My gcc default invocation for C99 catches 2 "comparison between signed and unsigned" (lines 48 and 80) and 1 "switch missing default case" (line 71) when compiling your code. – Smooth

Answer 2

You can also use +slashslashcomment when calling splint. In this case:

splint +slashslashcomment brainfuck.c

---

Splint Manual's Appendix B:

P:- slashslashcomment

A // comment is used. ISO C99 allows // comments, but earlier standards did not.

(would put this in a comment, but don't have the necessary rep)

Publicspirited