http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55541
Bug #: 55541
Summary: unable to see local variables due extra lexical block
was generated
Classification: Unclassified
Product: gcc
Version: 4.6.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: chihin...@oracle.com
There is a regression present gcc4.4.4: the compiler
generates a bogus lexical block marker in the debug info, more precisely
between the parameters and the local variables of functions. This is related
to http://gcc.gnu.org/ml/gcc-patches/2010-08/msg02111.html
This affect gdb/dbx behavior, that debugger users are not able to inspect local
variable value when stop at "}" line of a function, for detail, please refer to
gdb bugzilla
http://sourceware.org/bugzilla/show_bug.cgi?id=14850
for following test cast
int
main() {
int i;
i = 10;
}
if I stop at } of main and print i, gdb gave error:
tarting program: /home/chko/core/g++/g45/a.out
Breakpoint 1, main () at t.cc:4
4 i = 10;
(gdb) p i
$1 = 0
(gdb) n
5 }
(gdb) p i
No symbol "i" in current context.
(gdb)
This is due to "i" was within DW_TAG_lexical_block:
< 1><0x00000025> DW_TAG_subprogram
DW_AT_external yes(1)
DW_AT_name "main"
DW_AT_decl_file 0x00000001 /tmp/t.cc
DW_AT_decl_line 0x00000003
DW_AT_type <0x00000059>
DW_AT_low_pc 0x08050990
DW_AT_high_pc 0x080509a4
DW_AT_frame_base <loclist with 4 entries
follows>
[ 0]<lowpc=0x00000000><highpc=0x00000001>DW_OP_breg4+4
[ 1]<lowpc=0x00000001><highpc=0x00000003>DW_OP_breg4+8
[ 2]<lowpc=0x00000003><highpc=0x00000013>DW_OP_breg5+8
[ 3]<lowpc=0x00000013><highpc=0x00000014>DW_OP_breg4+4
DW_AT_GNU_all_call_sites yes(1)
DW_AT_sibling <0x00000059>
< 2><0x00000042> DW_TAG_lexical_block
DW_AT_low_pc 0x08050996
DW_AT_high_pc 0x0805099d
< 3><0x0000004b> DW_TAG_variable
DW_AT_name "i"
DW_AT_decl_file 0x00000001 /tmp/t.cc
DW_AT_decl_line 0x00000004
DW_AT_type <0x00000059>
DW_AT_location DW_OP_fbreg -12
< 1><0x00000059> DW_TAG_base_type
DW_AT_byte_size 0x00000004
DW_AT_encoding DW_ATE_signed
DW_AT_name "int"
