[Bug debug/96937] New: Duplicate DW_TAG_formal_parameter in out-of-line DW_TAG_subprogram instance

[simon.marchi at polymtl dot ca]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96937

            Bug ID: 96937
           Summary: Duplicate DW_TAG_formal_parameter in out-of-line
                    DW_TAG_subprogram instance
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
          Assignee: unassigned at gcc dot gnu.org
          Reporter: simon.marchi at polymtl dot ca
  Target Milestone: ---

While debugging GDB (compiled with GCC master and -O2) with GDB, I get:

972     do_examine (struct format_data fmt, struct gdbarch *gdbarch, CORE_ADDR
addr)
(top-gdb) frame
#0  do_examine (gdbarch=0x249a6b0, addr=0x400636, fmt=..., fmt=...) at
/home/smarchi/src/binutils-gdb/gdb/printcmd.c:972
972     do_examine (struct format_data fmt, struct gdbarch *gdbarch, CORE_ADDR
addr)

Note that the parameters shown by GDB aren't in the same order as in the
function declaration, and that "fmt" is duplicated.

0x0004e0bd:   DW_TAG_subprogram
                DW_AT_abstract_origin [DW_FORM_ref4]    (0x0004a912
"do_examine")
                ...

0x0004e0cd:     DW_TAG_formal_parameter
                  DW_AT_abstract_origin [DW_FORM_ref4]  (0x0004a92e "gdbarch")
                  ...

0x0004e0d6:     DW_TAG_formal_parameter
                  DW_AT_abstract_origin [DW_FORM_ref4]  (0x0004a93b "addr")
                  ...

0x0004e0df:     DW_TAG_variable
                  DW_AT_abstract_origin [DW_FORM_ref4]  (0x0004a948 "format")
                  ...

0x0004e0e8:     DW_TAG_variable
                  DW_AT_abstract_origin [DW_FORM_ref4]  (0x0004a955 "size")
                  ...

... some more variables ...


0x0004e130:     DW_TAG_formal_parameter
                  DW_AT_abstract_origin [DW_FORM_ref4]  (0x0004a921 "fmt")

0x0004e135:     DW_TAG_formal_parameter
                  DW_AT_abstract_origin [DW_FORM_ref4]  (0x0004a921 "fmt")


This matches what we see in GDB: the parameters are not in the same order as in
the function declaration and fmt is duplicated.  The abstract origin has them
correct:

0x0004a912:   DW_TAG_subprogram
                DW_AT_name [DW_FORM_strp]       ("do_examine")
                ...

0x0004a921:     DW_TAG_formal_parameter
                  DW_AT_name [DW_FORM_string]   ("fmt")
                  ...

0x0004a92e:     DW_TAG_formal_parameter
                  DW_AT_name [DW_FORM_strp]     ("gdbarch")
                  ...

0x0004a93b:     DW_TAG_formal_parameter
                  DW_AT_name [DW_FORM_strp]     ("addr")
                  ...

After reading bug #49828, I presume that the fact that the parameters are not
in the right order is not considered a bug.  GDB could cope with that by
sorting them to be in the same order as what's in the abstract origin.

However, having fmt there twice could maybe be considered a bug, hence I am
reporting it.

GDB commit (used as the debugged program):
c5cd900e4f197870812c2d3e2c194871c171ef42
GCC commit: 8ad3fc6ca46c603d9c3efe8e6d4a8f2ff1a893a4