The gcc compiler produces an internal compiler error when the option -mlong-double-128 is used on 
macosX 10.3.5 with gcc 3.4.1.

The  program (buggcc040910.c) is :

int  myprintf(const char * format, ...);

void main()
{
 myprintf("s=%d %LE\n",sizeof(long double),(long double)1.E0);
}

The intermerdiate file (buggcc040910.i) is : 

# 1 "buggcc040910.c"
# 1 "<built-in>"
# 1 "<command line>"
# 1 "buggcc040910.c"

int myprintf(const char * format, ...);

void main()
{
 myprintf("s=%d %LE\n",sizeof(long double),(long double)1.E0);
}


The command line is :
$ /Volumes/WORK/gastin/gcc341/bin/gcc -c -v -O0 -save-temps -mlong-double-128 
buggcc040910.c 
Reading specs from /Volumes/WORK/gastin/gcc341/lib/gcc/powerpc-apple-darwin7.5.0/3.4.1/specs
Configured with: ./configure --prefix=/Volumes/WORK/gastin/gcc341
Thread model: posix
gcc version 3.4.1
 /Volumes/WORK/gastin/gcc341/libexec/gcc/powerpc-apple-darwin7.5.0/3.4.1/cc1 -E -quiet -v 
-D__DYNAMIC__ buggcc040910.c -fPIC -mlong-double-128 -O0 -o buggcc040910.i
ignoring nonexistent directory "/usr/local/include"
ignoring nonexistent directory "/Volumes/WORK/gastin/gcc341/lib/gcc/powerpc-apple-darwin7.5.0/
3.4.1/../../../../powerpc-apple-darwin7.5.0/include"
#include "..." search starts here:
#include <...> search starts here:
 /Volumes/WORK/gastin/gcc341/include
 /Volumes/WORK/gastin/gcc341/lib/gcc/powerpc-apple-darwin7.5.0/3.4.1/include
 /usr/include
End of search list.
 /Volumes/WORK/gastin/gcc341/libexec/gcc/powerpc-apple-darwin7.5.0/3.4.1/cc1 -fpreprocessed 
buggcc040910.i -fPIC -quiet -dumpbase buggcc040910.c -mlong-double-128 -auxbase 
buggcc040910 -O0 -version -o buggcc040910.s
GNU C version 3.4.1 (powerpc-apple-darwin7.5.0)
        compiled by GNU C version 3.3 20030304 (Apple Computer, Inc. build 1666).
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
buggcc040910.c: In function `main':
buggcc040910.c:5: warning: return type of 'main' is not `int'
buggcc040910.c:7: error: insn does not satisfy its constraints:
(insn 14 24 25 (set (reg:DI 33 f1)
        (mem/u/f:DI (lo_sum:SI (reg:SI 2 r2)
                (const:SI (minus:SI (symbol_ref/u:SI ("*LC1") [flags 0x2])
                        (symbol_ref:SI ("<pic base>"))))) [0 S8 A64])) 327 {*movdi_internal32} (nil)
    (nil))
buggcc040910.c:7: internal compiler error: in final_scan_insn, at final.c:2359
Please submit a full bug report,
with preprocessed source if appropriate.
See <URL:http://gcc.gnu.org/bugs.html> for instructions.