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SubjectRe: sparse errors

On Wed, 28 May 2003, Ryan Anderson wrote:
>
> I'm not totally grokking how sparse is put together yet, but I've got
> this:
>
> Some symbols with type SYM_NODE are getting ctype->base_type==NULL,

This means they have no type at all, either because of a parse error, or
because the lazy evaluation hasn't evaluated it yet (ie it was a tad _too_
lazy).

> causing a segfault in type_difference:422. (If I work around that one,
> there's another spot at line 680. I started to follow what was going on
> a bit at that point and realized they were probably symptoms, not the
> actual bug, so I stopped working around it.)

Right.

The first thing to do is to see where it happens, in gdb do

up (to get to compatible_assignment_types)
p expr->pos (to get where in the soruce file it is)

it's triggered in cramfs_uncompress_block():

zlib_inflateReset(&stream);

on "stream", and the problem _seems_ to be that the target type for the
function call comparison is non-existent.

And that, in turn, seems to be because of the old K&R style function
prototype due to

#ifndef OF /* function prototypes */
# ifdef STDC
# define OF(args) args
# else
# define OF(args) ()
# endif
#endif
and check not defining STDC.

It appears to be fixed by just adding -DSTDC to the check command line, to
make zlib use ANSI prototypes.

In short: sparse doesn't handle K&R function declarations very well,
although clearly it shouldn't have segfaulted (it should have warned about
it). I don't know why it didn't warn.

> Oh, BTW, the way you have struct ctype_sym declared inside struct symbol
> confuses the crap out of gdb, but gcc appears to like it, so... *shrug*.

Yeah, gdb is crap when it comes to anonymous structures, but I can't live
without them these days, so..

> Should this be cc:ed to linux-kernel, or do you have another place in
> mind?

It probably shouldn't be CC'd to linux-kernel, but there isn't any other
place either.

Linus

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