Date: Tue, 2 May 95 00:04:03 CDT
From: csaba AT vuse DOT vanderbilt DOT edu (Csaba A. Biegl)
To: djgpp AT sun DOT soe DOT clarkson DOT edu
Subject: GAS bug


All versions of the i386 GAS I have tested (1.3.8, 2.1.1, 2.2.1) generate bad
code when compiling input which uses absolute addressing with segment overrides.
This is a not a DJGPP bug, this is a bug in GAS. Both the DOS (DJGPP) and
Unix I386 (Linux) binaries of several GAS versions exhibit the same bug.
Although I have already reported this to the GAS maintainers, I a posting
here too, because people who use GAS with DOS extenders are most likely
to encounter this bug.

The following gdb session illustrates the problem:


(gdb) r
Starting program: /usr2/tmp/x 

Breakpoint 1, main () at x.c:3
3               asm(
(gdb) l
1       main()
2       {
3               asm(
4                       "movl   %fs:0x1234,%eax;"
5                       "movl   %fs:(%ecx),%eax;"
6               );
7       }
(gdb) disass
Dump of assembler code for function main:
0x54 <main>:    pushl  %ebp
0x55 <main+1>:  movl   %esp,%ebp
0x57 <main+3>:  call   0xf8 <__main>
0x5c <main+8>:  movl   0x1234,%eax
0x61 <main+13>: movl   %fs:(%ecx),%eax
0x64 <main+16>: movl   %ebp,%esp
0x66 <main+18>: popl   %ebp
0x67 <main+19>: ret    
End of assembler dump.
(gdb) 

Csaba Biegl
csaba AT vuse DOT vanderbilt DOT edu