From mboxrd@z Thu Jan  1 00:00:00 1970
From: Robert Lipe <robertl@sco.com>
To: egcs-bugs@egcs.cygnus.com
Cc: gas2@cygnus.com
Subject: dwarf-1 egcs outputs bad .s / GAS allows it.
Date: Fri, 26 Mar 1999 19:32:00 -0000
Message-id: <19990326213126.A3658@rjlhome.sco.com>
X-SW-Source: 1999/msg00042.html

Two groups copied.  Decouple the respective alias from any conversation
that doesn't impact that group.  I'm not sure, but I think there are two
bugs.  The first bug is that EGCS emits this.  The second is that GAS
accepts it. :-)

EGCS off the trunk from this morning.   GAS is 990223.  Both configured
for Unixware 7 (i686-pc-sysv5).  I have no real reason to believe this
is target-specific other that dwarf-1 on x86 isn't a road well travelled.

I just analyzed the testsuite failure on bf-pack-1.c.  It takes all of 
'-O3 -fPIC -g' to trigger this bug on this case.

/home3/negcs/gcc/xgcc --save-temps -dA -B/home3/negcs/gcc/ /play/egcs/gcc/testsuite/gcc.c-torture/execute/bf-pack-1.c -w -O3 -g -lm -fPIC

.L_D8_e:
.L_D9:
        .4byte  .L_D9_e-.L_D9
        .2byte  0xd     / TAG_member
        .2byte  0x12    / AT_sibling
        .4byte  .L_D10
        .2byte  0x38    / AT_name
        .string "whole"
        .2byte  0x142   / AT_member
        .4byte  .L_T83
        .2byte  0x55    / AT_fund_type
        .2byte  0xc     / FT_unsigned_long
        .2byte  0xb6    / AT_byte_size
        .4byte  0x4
        .2byte  0xd6    / AT_bit_size
        .4byte  0x20
        .2byte  0xc5    / AT_bit_offset
HERE->  .2byte  0xfffffff0
        .2byte  0x23    / AT_location
        .2byte  .L_l9_e-.L_l9
.L_l9:
        .byte   0x4     / OP_CONST
        .4byte  0x0


This is coming from the end bit_offset_attribute() in dwarfout.c.  It
calls ASM_OUTPUT_DWARF_DATA2 but bit_offset is negative. ( I don't know
why it's negative but when you subtract 0x30 from 0x20 you do indeed get
a -0x10.)


Should bit_offset be masked to fit in 16 bits?   Should it be .4byte?
Should this be an impossible combination anyway?  Why does GAS allow this?