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

[Franz Sirl <Franz dot Sirl-kernel at lauterbach dot com>]

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.