in reply to Re: some help with inline C
in thread some help with inline C

almut, thanks. that did help a lot, i dont get segfaults right away anymore :) I can now run the code for a little bit before it segfaults, now with a different error message. I dont know too much about GDB, but this is what backtrace tells me. please give me any help on how i can provide you with more information. 
(gdb) backtrace
#0  0x00002aaaae17f1f9 in tag_parser (tag=0x2 <Address 0x2 out of boun
+ds>, len=-1216936334,
    back_tag=0x7fffffc91ac7 "") at getandParseWithC_pl_05fd.xs:52
#1  0x00002aaaae17f762 in parser (url=0x4cd9780 "openpolytechnic.ac.nz
+/ftp/linux/sunsite/docs/faqs/ftp-faq",
    doc=0x2aaab7770010 "HTTP/1.1 200 OK\r\nDate: Wed, 12 Oct 2005 01:1
+6:33 GMT\r\nServer: Apache/2.0.54 (Unix) mod_ssl/2.0.54 OpenSSL/0.9.7
+g DAV/2\r\nLast-Modified: Sun, 29 May 2005 11:11:07 GMT\r\nETag: \"19
+3b68-1ead-d3e728c0\"\r\nAcce"...,
    buf=0x153efac0 "openpolytechnic U\nac U\nnz U\nftp U\nlinux U\nsun
+site U\ndocs U\nfaqs U\nftp U\nfaq U\nftp P\nhowto P\nftp P\nfile P\n
+transfer P\nprotocol P\nis P\na P\nclient P\nserver P\ntcp P\nprotoco
+l P\nthat P\nallows P\na P\nuser P\nto"..., blen=16321) at getandPars
+eWithC_pl_05fd.xs:176
#2  0x00002aaaae17fb4a in MyParser (url=0x4cd9780 "openpolytechnic.ac.
+nz/ftp/linux/sunsite/docs/faqs/ftp-faq",
    page=0x2aaab7770010 "HTTP/1.1 200 OK\r\nDate: Wed, 12 Oct 2005 01:
+16:33 GMT\r\nServer: Apache/2.0.54 (Unix) mod_ssl/2.0.54 OpenSSL/0.9.
+7g DAV/2\r\nLast-Modified: Sun, 29 May 2005 11:11:07 GMT\r\nETag: \"1
+93b68-1ead-d3e728c0\"\r\nAcce"..., len=8160) at getandParseWithC_pl_0
+5fd.xs:310
#3  0x00002aaaae180dcb in XS_main_MyParser (my_perl=0x505010, cv=0xb36
+240) at getandParseWithC_pl_05fd.c:400
#4  0x000000398d69b67e in Perl_pp_entersub ()
   from /usr/lib64/perl5/5.8.6/x86_64-linux-thread-multi/CORE/libperl.
+so
#5  0x000000398d67f3cd in Perl_runops_debug ()
   from /usr/lib64/perl5/5.8.6/x86_64-linux-thread-multi/CORE/libperl.
+so
#6  0x000000398d639dbe in perl_run () from /usr/lib64/perl5/5.8.6/x86_
+64-linux-thread-multi/CORE/libperl.so
#7  0x0000000000401a01 in main ()

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As i said before, parser is a code that my research group has been using for some time with out problems.(though everyone else is a C guru, not perl) I suspect there is an issue with how my code is interacting with parser (or how the perl vars are passed into this C code)I will include the parser code for comleteness : 

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

#define PTAG_B    1
#define PTAG_I    2
#define    PTAG_H    3
#define PTAG_TITLE    4
#define PTAG_SCRIPT    5

#define _TITLE_TAG    0x0001
#define _B_TAG        0x0004
#define _H_TAG        0x0008
#define _I_TAG        0x0010

#define xl_isdigit(c) (((c) >= '0') && ((c) <= '9'))
#define xl_islower(c) (((c) >= 'a') && ((c) <= 'z'))
#define xl_isupper(c) (((c) >= 'A') && ((c) <= 'Z'))
#define xl_isindexable(c) (xl_isdigit(c) || xl_islower(c) || xl_isuppe
+r(c))
#define xl_tolower(c) ((c) += 'a' - 'A')

char* parser_init(char* doc)
{
    char *p;

    if (strncasecmp(doc, "HTTP/", 5))
        return NULL;
    
    for (p = doc; (*p != ' ')&&(*p); p++);
    if (*p == '\0')
        return NULL;

    if (atoi(p) != 200)
        return NULL;

    p = strstr(p,  "\\r\\n\\r\\n");
    if (p == NULL)
        return NULL;

    return p+4;
}

int tag_parser(char* tag, int len, char* back_tag)
{
    int i = 0;

    if (tag[0] == '/')
    {
        *back_tag = 1;
        i++;

    } else
        *back_tag = 0;

    switch (tag[i])
    {
    case 'b':
    case 'B':
    case 'i':
    case 'I':
        if (!isspace(tag[i+1]))
            return 0;
        if ((tag[i] == 'b') || (tag[i] == 'B'))
            return PTAG_B;
        return PTAG_I;

    case 'e':
    case 'E':
        i++;
        if (((tag[i]=='m')||(tag[i]=='M')) && (isspace(tag[i+1])))
            return PTAG_I;
        return 0;
    
    case 'h':
    case 'H':
        i++;
        if (((tag[i]>='1')&&(tag[i]<='6')) && (isspace(tag[i+1])))
            return PTAG_H;
        return 0;
    
    case 't':
    case 'T':
        i++;
        if ((0==strncasecmp(tag+i, "itle", 4)) && (isspace(tag[i+4])))
            return PTAG_TITLE;
        return 0;
    
    case 's':
    case 'S':
        i++;
        if ((0==strncasecmp(tag+i, "trong", 5)) && (isspace(tag[i+5]))
+)
            return PTAG_B;
        if ((0==strncasecmp(tag+i, "cript", 5)) && (isspace(tag[i+5]))
+)
            return PTAG_SCRIPT;
        return 0;

    default:
        break;
    }

    return 0;
}

#define xlbit_set(__b1, __b2)    ((__b1) |= (__b2))
#define xlbit_unset(__b1, __b2)    ((__b1) &= ~(__b2))
#define xlbit_check(__b1, __b2) ((__b1)&(__b2))

char* parser(char* url, char* doc, char* buf, int blen)
{

    char *p, *purl, *word, *ptag, *pbuf;
    char ch, back_tag, intag, inscript;
    unsigned tag_flag;
    int ret;

    p = parser_init(doc);
    if (p == NULL)
        return 0;
    pbuf = buf;

/* parsing URL */
    purl = url;
    while (*purl != '\0')
    {
        if (!xl_isindexable(*purl))
        {
            purl++;
            continue;
        }

        word = purl;
        while (xl_isindexable(*purl))
        {
            if (xl_isupper(*purl))
                xl_tolower(*purl);
            purl++;
        }

        ch = *purl;
        *purl = '\0';

        if (pbuf-buf+purl-word+3 > blen-1)
            return -1;
        sprintf(pbuf, "%s U\\n", word);
        pbuf += (purl-word)+3;

        *purl = ch;
    }

/* parsing page */
    tag_flag = 0;
    intag = 0;
    inscript = 0;

    while (*p != '\0')
    {
        if (!xl_isindexable(*p))
        {
            if (*p != '>')
            {
                if (*p == '<')
                {
                    ptag = p;
                    intag = 1;
                }
                p++;
                continue;
            }

            *p = ' ';
            ret = tag_parser(ptag+1, p-ptag, &back_tag);
            switch (ret)
            {
                case PTAG_B:

                    if (back_tag == 0)
                        xlbit_set(tag_flag, _B_TAG);
                    else
                        xlbit_unset(tag_flag, _B_TAG);
                    break;

                case PTAG_I:

                    if (back_tag == 0)
                        xlbit_set(tag_flag, _I_TAG);
                    else
                        xlbit_unset(tag_flag, _I_TAG);
                    break;

                case PTAG_H:

                if (back_tag == 0)
                    xlbit_set(tag_flag, _H_TAG);
                else
                    xlbit_unset(tag_flag, _H_TAG);
                break;

                case PTAG_TITLE:

                    if (back_tag == 0)
                        xlbit_set(tag_flag, _TITLE_TAG);
                    else
                        xlbit_unset(tag_flag, _TITLE_TAG);
                    break;

                case PTAG_SCRIPT:

                    if (back_tag == 0)
                        inscript = 1;
                    else
                        inscript = 0;

                default:
                    break;
            }

            intag = 0;
            p++;
            continue;
        }

        if (inscript || intag)
        {
            p++;
            continue;
        }

        word = p;
        while (xl_isindexable(*p))
        {
            if (xl_isupper(*p))
                xl_tolower(*p);
            p++;
        }

        ch = *p;
        *p = '\0';

        if (pbuf-buf+p-word+1 > blen-1)
            return -1;
        sprintf(pbuf, "%s ", word);
        pbuf += (p-word)+1;

        if (xlbit_check(tag_flag, _B_TAG))
        {
            if (pbuf-buf+1> blen-1)
                return -1;
            *pbuf = 'B';
            pbuf++;
        }

        if (xlbit_check(tag_flag, _H_TAG))
        {
            if (pbuf-buf+1> blen-1)
                return -1;
            *pbuf = 'H';
            pbuf++;
        }

        if (xlbit_check(tag_flag, _I_TAG))
        {
            if (pbuf-buf+1> blen-1)
                return -1;
            *pbuf = 'I';
            pbuf++;
        }

        if (xlbit_check(tag_flag, _TITLE_TAG))
        {
            if (pbuf-buf+1> blen-1)
                return -1;
            *pbuf = 'T';
            pbuf++;
        }

        if (tag_flag == 0)
        {
            if (pbuf-buf+1> blen-1)
                return -1;
            *pbuf = 'P';
            pbuf++;
        }

        if (pbuf-buf+1> blen-1)
            return -1;
        *pbuf = '\\n';
        pbuf++;
        *p = ch;
    }

    *pbuf = '\0';
    
    return pbuf-buf;
}

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Replies are listed 'Best First'.
Re^3: some help with inline C
by ikegami (Patriarch) on Oct 17, 2007 at 18:15 UTC 
    #0  0x00002aaaae17f1f9 in tag_parser (tag=0x2 <Address 0x2 out of boun
+ds>, len=-1216936334, back_tag=0x7fffffc91ac7 "") at getandParseWithC
+_pl_05fd.xs:52

    [download]

    shows that tag_parser is called with 2 for the first argument. That's obviously a bad pointer. The second argument is also obviously wrong.

    One possibility is that the input is something like foo>bar, which would cause tag_parser to be called before ptag is ever initialized. Did you try dumping what parser_init returns and finding out to which char p points?

    You're asking us to debug a C problem, you didn't provide any inputs, and you didn't provide any runnable code. The underlying cause could be a Perl problem, but you haven't gotten that far yet. Do you homework, then come back to us if it's Perl problem.

    Update: Added some details.

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Re^3: some help with inline C
by syphilis (Archbishop) on Oct 18, 2007 at 10:50 UTC
    Hi downer,

    When I run gcc -c parser.c I get a number of warnings "return makes pointer from integer without a cast". I think these occur because (the integer) -1 is being returned, even though the function is supposed to return a char*. I don't know if that causes any problems, but it's a bit agricultural, to say the least.

    I also got: 
    parser.c:287:11: warning: multi-character character constant
parser.c:287: warning: overflow in implicit constant conversion

    [download]
    Those warnings appear to me to be a little more sinister. They can be removed by changing line 287 from: 
                *pbuf = '\\n';

    [download]
    to: 
                *pbuf = '\n';

    [download]
    Does that change help your cause at all ?

    Given that we now have libparser.a (or, at least, have the capacity to build it), if you like to give us a (complete) sample Inline::C script that you're using, we might be able to make some real progress :-)

    Cheers,
    Rob
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