https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81001
Bug ID: 81001
Summary: incorrect debug info for parameter that is const
pointer to typedef of array
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: debug
Assignee: unassigned at gcc dot gnu.org
Reporter: ian at airs dot com
Target Milestone: ---
I am using a fairly recent trunk (SVN revision 248521).
Compiling this program gives me correct debug info:
typedef unsigned char Bar;
void foo(Bar* f){} // this works
void foo2(const Bar* f){} // this confuses cgo
void x() {
foo(0);
foo2(0);
}
Using readelf --debug=info, the debug info for foo's parameter is correctly
represented as a pointer to a typedef of unsigned char:
<2><a8>: Abbrev Number: 7 (DW_TAG_formal_parameter)
<a9> DW_AT_name : f
<ab> DW_AT_decl_file : 1
<ac> DW_AT_decl_line : 2
<ad> DW_AT_type : <0xb5>
<b1> DW_AT_location : 2 byte block: 91 68 (DW_OP_fbreg: -24)
<2><b4>: Abbrev Number: 0
<1><b5>: Abbrev Number: 8 (DW_TAG_pointer_type)
<b6> DW_AT_byte_size : 8
<b7> DW_AT_type : <0x2d>
<2d>: Abbrev Number: 2 (DW_TAG_typedef)
<2e> DW_AT_name : Bar
<32> DW_AT_decl_file : 1
<33> DW_AT_decl_line : 1
<34> DW_AT_type : <0x3d>
<3d>: Abbrev Number: 4 (DW_TAG_base_type)
<3e> DW_AT_byte_size : 1
<3f> DW_AT_encoding : 8 (unsigned char)
The debug info for foo2's parameter is also correctly represented as a pointer
to a const variant of the same typedef:
<2><78>: Abbrev Number: 7 (DW_TAG_formal_parameter)
<79> DW_AT_name : f
<7b> DW_AT_decl_file : 1
<7c> DW_AT_decl_line : 3
<7d> DW_AT_type : <0x85>
<81> DW_AT_location : 2 byte block: 91 68 (DW_OP_fbreg: -24)
<2><84>: Abbrev Number: 0
<1><85>: Abbrev Number: 8 (DW_TAG_pointer_type)
<86> DW_AT_byte_size : 8
<87> DW_AT_type : <0x38>
<38>: Abbrev Number: 3 (DW_TAG_const_type)
<39> DW_AT_type : <0x2d>
Compiling this similar program--changing the typedef from unsigned char to an
array of unsigned char--gives me incorrect debug info.
typedef unsigned char Bar[12];
void foo(Bar* f){} // this works
void foo2(const Bar* f){} // this confuses cgo
void x() {
foo(0);
foo2(0);
}
The debug info for foo's parameter is correct:
<2><ba>: Abbrev Number: 8 (DW_TAG_formal_parameter)
<bb> DW_AT_name : f
<bd> DW_AT_decl_file : 1
<be> DW_AT_decl_line : 2
<bf> DW_AT_type : <0xc7>
<c3> DW_AT_location : 2 byte block: 91 68 (DW_OP_fbreg: -24)
<2><c6>: Abbrev Number: 0
<1><c7>: Abbrev Number: 9 (DW_TAG_pointer_type)
<c8> DW_AT_byte_size : 8
<c9> DW_AT_type : <0x2d>
<2d>: Abbrev Number: 2 (DW_TAG_typedef)
<2e> DW_AT_name : Bar
<32> DW_AT_decl_file : 1
<33> DW_AT_decl_line : 1
<34> DW_AT_type : <0x38>
<38>: Abbrev Number: 3 (DW_TAG_array_type)
<39> DW_AT_type : <0x4f>
<3d> DW_AT_sibling : <0x48>
<4f>: Abbrev Number: 5 (DW_TAG_base_type)
<50> DW_AT_byte_size : 1
<51> DW_AT_encoding : 8 (unsigned char)
<52> DW_AT_name : (indirect string, offset: 0x86): unsigned char
But the debug info for foo2's parameter is incorrect:
<2><8a>: Abbrev Number: 8 (DW_TAG_formal_parameter)
<8b> DW_AT_name : f
<8d> DW_AT_decl_file : 1
<8e> DW_AT_decl_line : 3
<8f> DW_AT_type : <0x97>
<93> DW_AT_location : 2 byte block: 91 68 (DW_OP_fbreg: -24)
<2><96>: Abbrev Number: 0
<1><97>: Abbrev Number: 9 (DW_TAG_pointer_type)
<98> DW_AT_byte_size : 8
<99> DW_AT_type : <0x38>
As you can see, the debug info for foo2's parameter says that it is a pointer
to an array of unsigned char. The const qualifier has been lost. The fact
that it is a pointer to a typedef has been lost. What we should see here is
something like we saw for the first program: the pointer type should refer to a
DW_TAG_const_type that refers to the DW_TAG_typedef.
