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[Bug gdb/17450] New: resolve_dynamic_type_internal misunderstands check_typedef -> internal error
- From: "dje at google dot com" <sourceware-bugzilla at sourceware dot org>
- To: gdb-prs at sourceware dot org
- Date: Wed, 01 Oct 2014 17:57:24 +0000
- Subject: [Bug gdb/17450] New: resolve_dynamic_type_internal misunderstands check_typedef -> internal error
- Auto-submitted: auto-generated
https://sourceware.org/bugzilla/show_bug.cgi?id=17450
Bug ID: 17450
Summary: resolve_dynamic_type_internal misunderstands
check_typedef -> internal error
Product: gdb
Version: HEAD
Status: NEW
Severity: normal
Priority: P2
Component: gdb
Assignee: unassigned at sourceware dot org
Reporter: dje at google dot com
Clang is emitting no bounds info for the "x" in
class c { char x[0]; char more_x[42]; };
This causes has_static_range for "x" to return false (lower bound is defaulted
to zero, upper bound is unknown), which in turn causes is_dynamic_type to
return true and we enter resolve_dynamic_type (which is just a wrapper on
resolve_dynamic_type_internal).
In the example at hand (I don't have an easy to provide testcase, at least not
yet), the type is defined in another CU so what resolve_dynamic_type gets is an
opaque type. We then hit this assert in resolve_dynamic_struct and crash:
gdb_assert (TYPE_NFIELDS (type) > 0);
resolve_dynamic_type_internal seems to not understand that check_typedef has
(at least) two main purposes:
1) check for typedefs (duh ... :-)),
2) AND resolve opaque types.
It's easy to understand this happening given how poorly named check_typedef is.
static struct type *
resolve_dynamic_type_internal (struct type *type, CORE_ADDR addr,
int top_level)
{
struct type *real_type = check_typedef (type);
struct type *resolved_type = type;
const struct dynamic_prop *prop;
CORE_ADDR value;
if (!is_dynamic_type_internal (real_type, top_level))
return type;
switch (TYPE_CODE (type))
{
...
case TYPE_CODE_STRUCT:
resolved_type = resolve_dynamic_struct (type, addr);
break;
}
...
}
Note that we've called check_typedef, BUT we're passing type to
resolve_dynamic_struct not real_type. If type is an opaque type we in fact do
want to pass real_type to resolve_dynamic_struct.
Either that or call check_typedef again in resolve_dynamic_struct. Since this
collection of functions is all just implementation detail for
resolve_dynamic_type I'm ok with not sprinkling calls to check_typedef
everywhere it might be needed (and in fact since the function is so badly named
sprinkling it about doesn't improve readability). It would be reasonable to
create a resolve_opaque_type function that handles this part of what
check_typedef does, and use that instead, but I'm ok with just passing
real_type to resolve_dynamic_struct here.
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