[Bug c/71689] New: Missing dwarf info when using nested function

[asnast at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71689

            Bug ID: 71689
           Summary: Missing dwarf info when using nested function
           Product: gcc
           Version: 4.8.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asnast at gmail dot com
  Target Milestone: ---

Hello,

The following piece of code will fail to correctly generate dwarf function
signature information:

void outer(int *x)
{
    *x *= 2;
    void inner(void) { *x += 1; }
}

int main()
{
    return 0;
}

When compiling with "gcc -g <filename>" a DW_TAG_formal_parameter DIE is not
generated for 'x' parameter for outer function above:

dwarfdump -a ./a.out:
LOCAL_SYMBOLS:
< 1><0x0000002d>    DW_TAG_subprogram
                      DW_AT_external              yes(1)
                      DW_AT_name                  "outter"
                      DW_AT_decl_file             0x00000001 /home/alexsn/tst.c
                      DW_AT_decl_line             0x00000001
                      DW_AT_prototyped            yes(1)
                      DW_AT_low_pc                0x00400566
                      DW_AT_high_pc               <offset-from-lowpc>68
                      DW_AT_frame_base            len 0x0001: 9c:
DW_OP_call_frame_cfa
                      DW_AT_GNU_all_tail_call_sitesyes(1)
                      DW_AT_sibling               <0x0000005e>
< 2><0x0000004a>      DW_TAG_subprogram
...

Note that this only occurs if 'x' parameter if used from both outer and inner
function and removing either will correctly generate the missing DIE:

void outer(int *x)
{
    void inner(void) { *x += 1; }
}

or

void outer(int *x)
{
    *x *= 2;
    void inner(void) { }
}

Will generate:
LOCAL_SYMBOLS:
< 1><0x0000002d>    DW_TAG_subprogram
                      DW_AT_external              yes(1)
                      DW_AT_name                  "outter"
                      DW_AT_decl_file             0x00000001 /home/alexsn/tst.c
                      DW_AT_decl_line             0x00000001
                      DW_AT_prototyped            yes(1)
                      DW_AT_low_pc                0x00400566
                      DW_AT_high_pc               <offset-from-lowpc>58
                      DW_AT_frame_base            len 0x0001: 9c:
DW_OP_call_frame_cfa
                      DW_AT_GNU_all_tail_call_sitesyes(1)
                      DW_AT_sibling               <0x0000005e>
< 2><0x0000004a>      DW_TAG_formal_parameter
                        DW_AT_name                  "x"
                        DW_AT_decl_file             0x00000001
/home/alexsn/tst.c
                        DW_AT_decl_line             0x00000001
                        DW_AT_type                  <0x0000005e>

I've tested this on gcc 4.8.4 and gcc 5.3.1 both of which havethis issue.

Thanks, Alex.