This is the list of names "reserved to the implementation" 
that have been claimed by certain compilers of interest, and
should not be used in the library.  It will grow, of course.
We generally are interested in names that are not all-caps,
except for those like "_T"

For Solarix:
_B
_C
_L
_N
_P
_S
_U
_X
_E1
..
_E24

Irix adds:
_A
_G

MS adds:
_T

For GCC:

  [Note that this list is out of date.  It applies to the old
  name-mangling; in G++ 3.0 and higher a different name-mangling is
  used.  In addition, many of the bugs relating to G++ interpreting
  these names as operators have been fixed.]

  The full set of __* identifiers (combined from gcc/cp/lex.c and
  gcc/cplus-dem.c) that are either old or new, but are definitely 
  recognized by the demangler, is:

__aa
__aad
__ad
__addr
__adv
__aer
__als
__alshift
__amd
__ami
__aml
__amu
__aor
__apl
__array
__ars
__arshift
__as
__bit_and
__bit_ior
__bit_not
__bit_xor
__call
__cl
__cm
__cn
__co
__component
__compound
__cond
__convert
__delete
__dl
__dv
__eq
__er
__ge
__gt
__indirect
__le
__ls
__lt
__max
__md
__method_call
__mi
__min
__minus
__ml
__mm
__mn
__mult
__mx
__ne
__negate
__new
__nop
__nt
__nw
__oo
__op
__or
__pl
__plus
__postdecrement
__postincrement
__pp
__pt
__rf
__rm
__rs
__sz
__trunc_div
__trunc_mod
__truth_andif
__truth_not
__truth_orif
__vc
__vd
__vn

SGI badnames:
__builtin_alloca
__builtin_fsqrt
__builtin_sqrt
__builtin_fabs
__builtin_dabs
__builtin_cast_f2i
__builtin_cast_i2f
__builtin_cast_d2ll
__builtin_cast_ll2d
__builtin_copy_dhi2i
__builtin_copy_i2dhi
__builtin_copy_dlo2i
__builtin_copy_i2dlo
__add_and_fetch
__sub_and_fetch
__or_and_fetch
__xor_and_fetch
__and_and_fetch
__nand_and_fetch
__mpy_and_fetch
__min_and_fetch
__max_and_fetch
__fetch_and_add
__fetch_and_sub
__fetch_and_or
__fetch_and_xor
__fetch_and_and
__fetch_and_nand
__fetch_and_mpy
__fetch_and_min
__fetch_and_max
__lock_test_and_set
__lock_release
__lock_acquire
__compare_and_swap
__synchronize
__high_multiply
__unix
__sgi
__linux__
__i386__
__i486__
__cplusplus
__embedded_cplusplus
// long double conversion members mangled as __opr
// http://gcc.gnu.org/ml/libstdc++/1999-q4/msg00060.html
_opr