Re: debug/7241: DWARF encoding for "char" incorrect in gcc

[Franz Sirl <Franz.Sirl-kernel@lauterbach.com>]

The following reply was made to PR debug/7241; it has been noted by GNATS.

From: Franz Sirl <Franz.Sirl-kernel@lauterbach.com>
To: jcownie@etnus.com
Cc: gcc-gnats@gcc.gnu.org,gcc-bugs@gcc.gnu.org
Subject: Re: debug/7241: DWARF encoding for "char" incorrect in gcc
Date: Tue, 09 Jul 2002 13:04:25 +0200

 At 12:01 09.07.2002, jcownie@etnus.com wrote:
 
 > >Number:         7241
 > >Category:       debug
 > >Synopsis:       DWARF encoding for "char" incorrect in gcc
 > >Confidential:   no
 > >Severity:       serious
 > >Priority:       medium
 > >Responsible:    unassigned
 > >State:          open
 > >Class:          sw-bug
 > >Submitter-Id:   net
 > >Arrival-Date:   Tue Jul 09 03:06:00 PDT 2002
 > >Closed-Date:
 > >Last-Modified:
 > >Originator:     James Cownie
 > >Release:        3.1
 > >Organization:
 >Etnus LLC
 > >Environment:
 >System: Linux pc4 2.4.18 #1 Tue Apr 2 10:17:01 BST 2002 i686 unknown
 >Architecture: i686
 >host: i686-pc-linux-gnu
 >build: i686-pc-linux-gnu
 >target: i686-pc-linux-gnu
 >configured with: /home1/GNU/gcc-3.1/configure
 >
 > >Description:
 >The DWARF emitted for a "char" variable is incorrect from gcc, but
 >correct from g++.
 >
 >Consider this code
 >---- const_strings.c ---------
 >typedef struct
 >{
 >   const char * name;
 >   int value;
 >} named_value;
 >
 >int main (int argc, char ** argv)
 >{
 >   named_value v;
 >   const char * zero = "zero";
 >
 >   v.name = "one";
 >   v.value = 1;
 >
 >   v.value++;
 >}
 >-------------------------------
 >jcownie@pc4: gcc31 -v -g -c const_strings.c
 >Reading specs from /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.1/specs
 >Configured with: /home1/GNU/gcc-3.1/configure
 >Thread model: single
 >gcc version 3.1
 >  /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.1/cc1 -lang-c -v -iprefix 
 > /home1/jim/bin/Linux-i686/../lib/gcc-lib/i686-pc-linux-gnu/3.1/ 
 > -D__GNUC__=3 -D__GNUC_MINOR__=1 -D__GNUC_PATCHLEVEL__=0 -D__ELF__ -Dunix 
 > -D__gnu_linux__ -Dlinux -D__ELF__ -D__unix__ -D__gnu_linux__ -D__linux__ 
 > -D__unix -D__linux -Asystem=posix -D__NO_INLINE__ -D__STDC_HOSTED__=1 
 > -Acpu=i386 -Amachine=i386 -Di386 -D__i386 -D__i386__ -D__tune_i686__ 
 > -D__tune_pentiumpro__ const_strings.c -quiet -dumpbase const_strings.c -g 
 > -version -o /tmp/ccStmXSo.s
 >GNU CPP version 3.1 (cpplib) (i386 Linux/ELF)
 >GNU C version 3.1 (i686-pc-linux-gnu)
 >         compiled by GNU C version 3.1.
 >ignoring nonexistent directory 
 >"/home1/jim/bin/Linux-i686/../lib/gcc-lib/i686-pc-linux-gnu/3.1/include"
 >ignoring nonexistent directory 
 >"/home1/jim/bin/Linux-i686/../lib/gcc-lib/i686-pc-linux-gnu/3.1/../../../../i686-pc-linux-gnu/include"
 >ignoring nonexistent directory "NONE/include"
 >ignoring nonexistent directory "/usr/local/i686-pc-linux-gnu/include"
 >#include "..." search starts here:
 >#include <...> search starts here:
 >  /usr/local/include
 >  /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.1/include
 >  /usr/include
 >End of search list.
 >  as --traditional-format -V -Qy -o const_strings.o /tmp/ccStmXSo.s
 >GNU assembler version 2.12 (i686-pc-linux-gnu) using BFD version 2.12
 >
 >If we dump out the DWARF info with readelf -wi we see that the
 >definition of the base type "char" is
 >
 >  <1><a0>: Abbrev Number: 6 (DW_TAG_base_type)
 >      DW_AT_name        : char
 >      DW_AT_byte_size   : 1
 >      DW_AT_encoding    : 5      (signed)
 >
 >Which (see page 62 of the DWARF 3 document) defines it as a signed
 >binary integer of size one byte, _NOT_ a signed character (which would
 >be encoding 6).
 >
 >If we do the same thing with g++, we get
 >  <1><d7>: Abbrev Number: 5 (DW_TAG_base_type)
 >      DW_AT_name        : char
 >      DW_AT_byte_size   : 1
 >      DW_AT_encoding    : 6      (signed char)
 >
 >which is correct.
 
 Hmm, I would rather think g++ is the wrong one here. IIRC in C++ (C too?) 
 "char"/"signed char"/"unsigned char" are actually 3 distinct types and thus 
 encoding 6 should have only be used if you would have explicitly written 
 "signed char" in your example, or?
 
 Franz.