https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109902
Bug ID: 109902
Summary: gcc/g++ emits wrong column number in DWARF
Product: gcc
Version: 12.3.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: debug
Assignee: unassigned at gcc dot gnu.org
Reporter: simon.farre.cx at gmail dot com
Target Milestone: ---
Created attachment 55111
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55111&action=edit
Contains GCC & clang dwarfdump output as well as simple source code.
The DWARF spec, states in paragraph 2.14 "Declaration Coordinates" (version 5,
https://dwarfstd.org/doc/DWARF5.pdf) that:
"The value of the DW_AT_decl_column attribute represents the source column
number at which the first character of the identifier of the declared object
appears. The value 0 indicates that no column has been specified."
Below is an example of contrived C++ code:
auto b = setfoo().setbar().setbaz();
gcc emits column meta data at these positions (represented by _):
auto b = setfoo_().setbar_().setbaz_();
Whereas for instance clang emits it properly, according to spec:
auto b = _setfoo()._setbar()._setbaz();
So for the following code:
" const auto res1 = b.set_foo (10).set_bar (20).set_baz (30).finalize ([]
(auto v) { return v * 2; });"
The following line number program is emitted (the line number is 66 and set_foo
begins on column position 23)
Address Line Column File ISA Discriminator Flags
------------------ ------ ------ ------ --- ------------- -------------
0x0000000000401150 66 31 1 0 0 is_stmt
0x0000000000401161 66 44 1 0 0 is_stmt
0x000000000040116e 66 57 1 0 0 is_stmt
0x000000000040117b 66 71 1 0 0 is_stmt
0x000000000040126c 66 72 1 0 0 is_stmt
0x0000000000401277 66 97 1 0 0 is_stmt
0x000000000040127c 66 100 1 0 0 is_stmt
Where as clang emits:
0x000000000040114b 66 23 1 0 0 is_stmt
0x000000000040115e 66 36 1 0 0
0x0000000000401171 66 49 1 0 0
0x0000000000401179 66 62 1 0 0
0x0000000000401430 66 0 1 0 0 is_stmt
0x000000000040143b 66 93 1 0 0 is_stmt prologue_end
0x000000000040143e 66 95 1 0 0
0x0000000000401441 66 86 1 0 0
It's also questionable if GCC emits the correct meta data with respect to
statements, but I guess that's a different issue.
