http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54181
Bug #: 54181
Summary: partial DW_TAG_class_type generated with
DW_AT_byte_size and without DW_AT_declaration
Classification: Unclassified
Product: gcc
Version: 4.7.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: debug
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: m...@gcc.gnu.org
Take the following program:
::::::::::::::
header.hxx
::::::::::::::
#include <malloc.h>
class Heap
{
private:
char *_memory;
size_t _size;
public:
Heap();
void* allocate (size_t size);
static size_t header_size();
};
::::::::::::::
heap.cxx
::::::::::::::
#include "header.hxx"
size_t
Heap::header_size ()
{
return 42;
}
Heap::Heap()
{
_size = header_size () + 32;
_memory = (char *) malloc (_size);
}
void*
Heap::allocate(size_t size)
{
_size += size;
return _memory + header_size();
}
::::::::::::::
main.cxx
::::::::::::::
#include "header.hxx"
int size (int resize)
{
return (int)Heap::header_size() - resize;
}
int
main (int argc, char **argv)
{
return size (argc);
}
Compile it with g++ 4.7.1:
$ g++ -g -O2 -c main.cxx
$ g++ -g -O2 -c heap.cxx
$ g++ -g main.o heap.o -o prog
Inspect it with:
$ eu-readelf --debug-dump=info prog
[...]
[ b] compile_unit
producer (strp) "GNU C++ 4.7.1 20120629 (Red Hat
4.7.1-1) -fpreprocessed -mtune=generic -march=x86-64 -g -O2"
language (data1) C++ (4)
name (strp) "main.cxx"
comp_dir (strp) "/home/mark/src/tests/cxx-decl"
ranges (sec_offset) range list [ 0]
low_pc (addr) 000000000000000000
stmt_list (sec_offset) 0
[...]
[ 289] class_type
name (strp) "Heap"
byte_size (data1) 16
decl_file (data1) 6
decl_line (data1) 3
sibling (ref4) [ 2a6]
[ 295] subprogram
external (flag_present) Yes
name (strp) "header_size"
decl_file (data1) 6
decl_line (data1) 11
linkage_name (strp) "_ZN4Heap11header_sizeEv"
type (ref4) [ 30]
accessibility (data1) public (1)
declaration (flag_present) Yes
[ 38e] compile_unit
producer (strp) "GNU C++ 4.7.1 20120629 (Red Hat
4.7.1-1) -fpreprocessed -mtune=generic -march=x86-64 -g -O2"
language (data1) C++ (4)
name (strp) "heap.cxx"
comp_dir (strp) "/home/mark/src/tests/cxx-decl"
low_pc (addr) 0x00000000004005b0
<_ZN4Heap11header_sizeEv>
high_pc (addr) 0x00000000004005ec
stmt_list (sec_offset) 220
[...]
[ 610] class_type
name (strp) "Heap"
byte_size (data1) 16
decl_file (data1) 5
decl_line (data1) 3
sibling (ref4) [ 67e]
[ 61c] member
name (strp) "_memory"
decl_file (data1) 5
decl_line (data1) 6
type (ref4) [ 412]
data_member_location (data1) 0
[ 628] member
name (strp) "_size"
decl_file (data1) 5
decl_line (data1) 7
type (ref4) [ 3b7]
data_member_location (data1) 8
[ 634] subprogram
external (flag_present) Yes
name (strp) "Heap"
decl_file (data1) 5
decl_line (data1) 9
accessibility (data1) public (1)
declaration (flag_present) Yes
object_pointer (ref4) [ 644]
sibling (ref4) [ 64a]
[ 644] formal_parameter
type (ref4) [ 67e]
artificial (flag_present) Yes
[ 64a] subprogram
external (flag_present) Yes
name (strp) "allocate"
decl_file (data1) 5
decl_line (data1) 10
linkage_name (strp) "_ZN4Heap8allocateEm"
type (ref4) [ 410]
accessibility (data1) public (1)
declaration (flag_present) Yes
object_pointer (ref4) [ 662]
sibling (ref4) [ 66d]
[ 662] formal_parameter
type (ref4) [ 67e]
artificial (flag_present) Yes
[ 667] formal_parameter
type (ref4) [ 3b7]
[ 66d] subprogram
external (flag_present) Yes
name (strp) "header_size"
decl_file (data1) 5
decl_line (data1) 11
linkage_name (strp) "_ZN4Heap11header_sizeEv"
type (ref4) [ 3b7]
accessibility (data1) public (1)
declaration (flag_present) Yes
Note how the first one in the main.cxx compile_unit is incomplete.
It only contains the header_size subprogram member (since that is the only
member used in main.cxx).
By just looking at the class_type DIE we cannot tell which one we need, since
both [ 289] and [ 610] look identical, both have a byte_size attribute and
neither is marked as declaration.
Shouldn't DIE [ 289] somehow be marked as partial? Either by not setting
DW_AT_byte_size and/or adding DW_AT_declaration?
This causes systemtap bug http://sourceware.org/bugzilla/show_bug.cgi?id=14434
"dwflpp sometimes caches incomplete class_type".
