Debug format (-g -ggdb -gstabs ...)

[Gordon Sadler]

I hope someone can explain this better.

gdb 5.0 info gdb:
Support...C...
 For best results when using GNU C++, use the stabs debugging format.
 You can select that format explicitly with the `g++' command-line
 options `-gstabs' or `-gstabs+'.

gcc 2.95.3 info gcc:
Invoking GCC...Debugging Options...
 
 `-g'
      Produce debugging information in the operating system's native
      format (stabs, COFF, XCOFF, or DWARF).  GDB can work with this
      debugging information.

      On most systems that use stabs format, `-g' enables use of extra
      debugging information that only GDB can use; this extra information
      makes debugging work better in GDB but will probably make other
      debuggers crash or refuse to read the program.  If you want to
      control for certain whether to generate the extra information, use
      `-gstabs+', `-gstabs', `-gxcoff+', `-gxcoff', `-gdwarf-1+', or
      `-gdwarf-1' (see below).
...

`-ggdb'
     Produce debugging information for use by GDB.  This means to use
     the most expressive format available (DWARF 2, stabs, or the
     native format if neither of those are supported), including GDB
     extensions if at all possible.

My understanding:
1. Using -g is the standard if you use gdb.
2. Using -ggdb should provide even more/better info for gdb to use.
3. gdb wants/uses -gstabs{+} for c++.

cat test.cpp
#include<stdio.h>
 
 int main()
 {
     printf("hello ... \n");
     return 0;
 }

ls -l a.out ggdb gstabs* dwarf2
-rwxr-xr-x    1 gbsadler gbsadler    17773 Apr 22 01:25 a.out
-rwxr-xr-x    1 gbsadler gbsadler    15345 Apr 22 01:31 dwarf2
-rwxr-xr-x    1 gbsadler gbsadler    15345 Apr 22 01:26 ggdb
-rwxr-xr-x    1 gbsadler gbsadler    14261 Apr 22 01:26 gstabs
-rwxr-xr-x    1 gbsadler gbsadler    17773 Apr 22 01:26 gstabs_p

a.out    is -g
dwarf2   is -gdwarf-2
ggdb     is -ggdb
gstabs   is -gstabs
gstabs_p is -gstabs+

So, apparently -g does use/produce a file with gstabs+. My question is,
why then does -ggdb not use gstabs+ for c++? Is -ggdb misdocumented?
Apparently -ggdb uses dwarf2... Is this 'correct'?

Same results with gcc (2.95.3) and test.c (test.cpp renamed).

Gordon Sadler