Assertion failure in `parse_pagenode`

mentioned in merge request !29 (merged)

I could not reproduce this fault and it's not immediately clear which line caused this assertion failure. There are two candidates:

4509:                                HParsedToken *res_strm = H_INDEX_TOKEN(contents, 1);

4530:                        HParsedToken *res_strm = H_INDEX_TOKEN(contents, 1);

The first of the two already carries the following context...

            else if (contents->token_type == TT_SEQUENCE)
                ...
            else {
                    // XXX contents->token_type != TT_SEQUENCE, but we're accessing contents->seq!?
                    // XXX what is this code supposed to do? --pesco
                    if(contents->seq->used >= 1)
                    ...

I cannot reproduce this (with current master or commit 88d933d6). It does not appear to hit either of the two lines in question at all and exits with 0. What gives...

Because the piece of code in question contains an obvious flaw regardless (XXX above), I'm looking at its origin. This section mainly originates from commits 285b6f89 and ddf109c3. The former introduces the branch on contents->token_type == TT_Objstm (calls parse_rsrcdict rather than dissecting an HSequence) and the latter works around a crash by essentially short-circuiting the TT_SEQUENCE case, leaving the sequence code as the broken else case it is now.

I am not sure whether that old TT_SEQUENCE code is supposed to be reachable (or present) at all. I would like to know an exact crash case that ddf109c3 guarded against.

mentioned in merge request !30 (merged)

Testing on commit d97574 , the most recent one it appears on.

pdf: pdf.c:4495: parse_pagenode: Assertion `entry->token_type == (HTokenType)TT_SEQUENCE' failed.

Program received signal SIGABRT, Aborted.

(gdb) bt
#0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:49
#1  0x00007ffff7da2546 in __GI_abort () at abort.c:79
#2  0x00007ffff7da242f in __assert_fail_base (fmt=0x7ffff7f18df8 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n", assertion=0x5555555700c0 "entry->token_type == (HTokenType)TT_SEQUENCE",
    file=0x55555556b010 "pdf.c", line=4495, function=<optimized out>) at assert.c:92
#3  0x00007ffff7db1222 in __GI___assert_fail (assertion=0x5555555700c0 "entry->token_type == (HTokenType)TT_SEQUENCE", file=0x55555556b010 "pdf.c", line=4495,
    function=0x5555555710f8 <__PRETTY_FUNCTION__.6386> "parse_pagenode") at assert.c:101
#4  0x00005555555668ac in parse_pagenode (aux=0x7fffffffde50, myNode=0x555555a46cf0, myRef=0x555555a293c0, myDict=0x555555a4ef18, parent_t=0x5555559d36e0, parent_n=0x7fffffffdea0,
    arena=0x555555a0e410) at pdf.c:4495
#5  0x000055555556754c in parse_pagetree (aux=0x7fffffffde50, myNode=0x7fffffffdea0, myRef=0x5555559d36e0, myDict=0x555555a15548, parent_t=0x0, parent_n=0x0) at pdf.c:4706
#6  0x00005555555677cd in parse_catalog (aux=0x7fffffffde50, root=0x5555559949e0) at pdf.c:4780
#7  0x000055555556907a in parse_xrefs (aux=0x7fffffffde50) at pdf.c:5394
#8  0x0000555555569482 in main (argc=1, argv=0x7fffffffe0e0) at pdf.c:5533

(gdb) frame 4
#4  0x00005555555668ac in parse_pagenode (aux=0x7fffffffde50, myNode=0x555555a46cf0, myRef=0x555555a293c0, myDict=0x555555a4ef18, parent_t=0x5555559d36e0, parent_n=0x7fffffffdea0,
    arena=0x555555a0e410) at pdf.c:4495
4495                            HParsedToken *res_strm = H_INDEX_TOKEN(entry, 1);
(gdb) list
4490                            entry = H_INDEX_TOKEN(contents, i);
4491                            entry = resolve_item(aux, entry, &nOffset, p_byteostm);
4492                            if (!entry) {  // TODO: Failure ==> xref error -- Figure out how to handle
4493                                    goto end;
4494                            }
4495                            HParsedToken *res_strm = H_INDEX_TOKEN(entry, 1);
4496                            HParseResult *bstrm_r = H_CAST(HParseResult, res_strm);
4497                            if ( (bstrm_r) && (bstrm_r->ast) ) {
4498                                    pieces[i] = bstrm_r->ast;
4499                                    bstrm = H_CAST_BYTES(bstrm_r->ast);

The token in question:

(gdb) p *entry
$1 = {token_type = 67, {bytes = {token = 0x5555601236a8 "\004", len = 0}, sint = 93825172387496, uint = 93825172387496, dbl = 4.6355794391794503e-310, flt = 4.21431724e+19,
    seq = 0x5555601236a8, user = 0x5555601236a8}, index = 0, bit_length = 0, bit_offset = 0 '\000'}
(gdb) p TT_Dict
$2 = 67

At the moment I couldn't reproduce the issue on commit 005b97ec, but judging from past results, it was on line 4509. The corresponding line in pdf.c at that commit:

4507                         if(contents->seq->used >= 2)
4508                         {
4509                                 HParsedToken *res_strm = H_INDEX_TOKEN(contents, 1);
4510                                 if (res_strm->token_type == TT_SEQUENCE) { // this seems like a big assumption
4511                                         myNode->pn.textStream = res_strm;
4512
4513                                 }
4514                                 else
4515                                         myNode->pn.textStream = NULL;
4516                         }

closed with merge request !30 (merged)

reopened

Since this seems to no longer trigger and the code in question was extensively reworked (!32 (merged)), I'm inclined to close.

closed

marked this issue as related to #33

Assertion failure in `parse_pagenode`

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