xsh_chap02_02.html

IEEE 1003.1-2003, Single Unix Specification v3

</table>

<br>
<p>The following identifiers are reserved regardless of the inclusion of headers:</p>

<ol>
<li>
<p>All identifiers that begin with an underscore and either an uppercase letter or another underscore are always reserved for any
use by the implementation.</p>
</li>

<li>
<p>All identifiers that begin with an underscore are always reserved for use as identifiers with file scope in both the ordinary
identifier and tag name spaces.</p>
</li>

<li>
<p>All identifiers in the table below are reserved for use as identifiers with external linkage. Some of these identifiers do not
appear in this volume of IEEE&nbsp;Std&nbsp;1003.1-2001, but are reserved for future use by the ISO&nbsp;C standard.</p>

<center>
<table cellpadding="3" align="center">
<tr valign="top">
<td align="left">
<p class="tent"><br>
_Exit<br>
abort<br>
abs<br>
acos<br>
acosf<br>
acosh<br>
acoshf<br>
acoshl<br>
acosl<br>
acosl<br>
asctime<br>
asin<br>
asinf<br>
asinh<br>
asinhf<br>
asinhl<br>
asinl<br>
asinl<br>
atan<br>
atan2<br>
atan2f<br>
atan2l<br>
atanf<br>
atanf<br>
atanh<br>
atanh<br>
atanhf<br>
atanhl<br>
atanl<br>
atanl<br>
atexit<br>
atof<br>
atoi<br>
atol<br>
atoll<br>
bsearch<br>
cabs<br>
cabsf<br>
cabsl<br>
cacos<br>
cacosf<br>
cacosh<br>
cacoshf<br>
cacoshl<br>
cacosl<br>
calloc<br>
carg<br>
cargf<br>
cargl<br>
casin<br>
casinf<br>
casinh<br>
casinhf<br>
casinhl<br>
casinl<br>
catan<br>
catanf<br>
catanh<br>
catanh<br>
catanhf<br>
catanhf<br>
catanhl<br>
catanhl<br>
catanl<br>
cbrt<br>
cbrtf<br>
cbrtl<br>
ccos<br>
ccosf<br>
ccosh<br>
ccoshf<br>
ccoshl<br>
ccosl<br>
ceil<br>
ceilf<br>
ceilf<br>
ceill<br>
ceill<br>
cerf<br>
cerfc<br>
cerfcf<br>
cerfcl<br>
cerff<br>
cerfl<br>
</p>
</td>
<td align="left">
<p class="tent"><br>
cexmp1<br>
cexmp1f<br>
cexmp1l<br>
cexp<br>
cexp2<br>
cexp2f<br>
cexp2l<br>
cexpf<br>
cexpl<br>
cimag<br>
cimagf<br>
cimagl<br>
clearerr<br>
clgamma<br>
clgammaf<br>
clgammal<br>
clock<br>
clog<br>
clog10<br>
clog10f<br>
clog10l<br>
clog1p<br>
clog1pf<br>
clog1pl<br>
clog2<br>
clog2f<br>
clog2l<br>
clogf<br>
clogl<br>
conj<br>
conjf<br>
conjl<br>
copysign<br>
copysignf<br>
copysignl<br>
cos<br>
cosf<br>
cosh<br>
coshf<br>
coshl<br>
cosl<br>
cpow<br>
cpowf<br>
cpowl<br>
cproj<br>
cprojf<br>
cprojl<br>
creal<br>
crealf<br>
creall<br>
csin<br>
csinf<br>
csinh<br>
csinhf<br>
csinhl<br>
csinl<br>
csqrt<br>
csqrtf<br>
csqrtl<br>
ctan<br>
ctanf<br>
ctanl<br>
ctgamma<br>
ctgammaf<br>
ctgammal<br>
ltime<br>
difftime<br>
div<br>
erfcf<br>
erfcl<br>
erff<br>
erfl<br>
errno<br>
exit<br>
exp<br>
exp2<br>
exp2f<br>
exp2l<br>
expf<br>
expl<br>
expm1<br>
expm1f<br>
expm1l<br>
fabs<br>
</p>
</td>
<td align="left">
<p class="tent"><br>
fabsf<br>
fabsl<br>
fclose<br>
fdim<br>
fdimf<br>
fdiml<br>
feclearexcept<br>
fegetenv<br>
fegetexceptflag<br>
fegetround<br>
feholdexcept<br>
feof<br>
feraiseexcept<br>
ferror<br>
fesetenv<br>
fesetexceptflag<br>
fesetround<br>
fetestexcept<br>
feupdateenv<br>
fflush<br>
fgetc<br>
fgetpos<br>
fgets<br>
fgetwc<br>
fgetws<br>
floor<br>
floorf<br>
floorl<br>
fma<br>
fmaf<br>
fmal<br>
fmax<br>
fmaxf<br>
fmaxl<br>
fmin<br>
fminf<br>
fminl<br>
fmod<br>
fmodf<br>
fmodl<br>
fopen<br>
fprintf<br>
fputc<br>
fputs<br>
fputwc<br>
fputws<br>
fread<br>
free<br>
freopen<br>
frexp<br>
frexpf<br>
frexpl<br>
fscanf<br>
fseek<br>
fsetpos<br>
ftell<br>
fwide<br>
fwprintf<br>
fwrite<br>
fwscanf<br>
getc<br>
getchar<br>
getenv<br>
gets<br>
getwc<br>
getwchar<br>
gmtime<br>
hypotf<br>
hypotl<br>
ilogb<br>
ilogbf<br>
ilogbl<br>
imaxabs<br>
imaxdiv<br>
is[a-z]*<br>
isblank<br>
iswblank<br>
labs<br>
ldexp<br>
ldexpf<br>
ldexpl<br>
ldiv<br>
ldiv<br>
lgammaf<br>
</p>
</td>
<td align="left">
<p class="tent"><br>
lgammal<br>
llabs<br>
llrint<br>
llrintf<br>
llrintl<br>
llround<br>
llroundf<br>
llroundl<br>
localeconv<br>
localtime<br>
log<br>
log10<br>
log10f<br>
log10l<br>
log1p<br>
log1pf<br>
log1pl<br>
log2<br>
log2f<br>
log2l<br>
logb<br>
logbf<br>
logbl<br>
logf<br>
logl<br>
longjmp<br>
lrint<br>
lrintf<br>
lrintl<br>
lround<br>
lroundf<br>
lroundl<br>
malloc<br>
mblen<br>
mbrlen<br>
mbrtowc<br>
mbsinit<br>
mbsrtowcs<br>
mbstowcs<br>
mbtowc<br>
mem[a-z]*<br>
mktime<br>
modf<br>
modff<br>
modfl<br>
nan<br>
nanf<br>
nanl<br>
nearbyint<br>
nearbyintf<br>
nearbyintl<br>
nextafterf<br>
nextafterl<br>
nexttoward<br>
nexttowardf<br>
nexttowardl<br>
perror<br>
pow<br>
powf<br>
powl<br>
printf<br>
putc<br>
putchar<br>
puts<br>
putwc<br>
putwchar<br>
qsort<br>
raise<br>
rand<br>
realloc<br>
remainderf<br>
remainderl<br>
remove<br>
remquo<br>
remquof<br>
remquol<br>
rename<br>
rewind<br>
rint<br>
rintf<br>
rintl<br>
round<br>
roundf<br>
roundl<br>
</p>
</td>
<td align="left">
<p class="tent"><br>
scalbln<br>
scalblnf<br>
scalblnl<br>
scalbn<br>
scalbnf<br>
scalbnl<br>
scanf<br>
setbuf<br>
setjmp<br>
setlocale<br>
setvbuf<br>
signal<br>
sin<br>
sinf<br>
sinh<br>
sinhf<br>
sinhl<br>
sinl<br>
sprintf<br>
sqrt<br>
sqrtf<br>
sqrtl<br>
srand<br>
sscanf<br>
str[a-z]*<br>
strtof<br>
strtoimax<br>
strtold<br>
strtoll<br>
strtoull<br>
strtoumax<br>
swprintf<br>
swscanf<br>
system<br>
tan<br>
tanf<br>
tanh<br>
tanhf<br>
tanhl<br>
tanl<br>
tgamma<br>
tgammaf<br>
tgammal<br>
time<br>
tmpfile<br>
tmpnam<br>
to[a-z]*<br>
trunc<br>
truncf<br>
truncl<br>
ungetc<br>
ungetwc<br>
va_end<br>
vfprintf<br>
vfscanf<br>
vfwprintf<br>
vfwscanf<br>
vprintf<br>
vscanf<br>
vsprintf<br>
vsscanf<br>
vswprintf<br>
vswscanf<br>
vwprintf<br>
vwscanf<br>
wcrtomb<br>
wcs[a-z]*<br>
wcstof<br>
wcstoimax<br>
wcstold<br>
wcstoll<br>
wcstoull<br>
wcstoumax<br>
wctob<br>
wctomb<br>
wctrans<br>
wctype<br>
wcwidth<br>
wmem[a-z]*<br>
wprintf<br>
wscanf<br>
</p>
</td>
</tr>
</table>
</center>

<basefont size="2"> 

<dl>
<dt><b>Note:</b></dt>

<dd>The notation [a-z] indicates any lowercase letter in the portable character set. The notation <tt>'*'</tt> indicates any
combination of digits, letters in the portable character set, or underscore.</dd>
</dl>

<basefont size="3"></li>

<li>
<p>All functions and external identifiers defined in the Base Definitions volume of IEEE&nbsp;Std&nbsp;1003.1-2001, <a href=
"../basedefs/xbd_chap13.html#tag_13">Chapter 13, Headers</a> are reserved for use as identifiers with external linkage.</p>
</li>

<li>
<p>All the identifiers defined in this volume of IEEE&nbsp;Std&nbsp;1003.1-2001 that have external linkage are always reserved for
use as identifiers with external linkage.</p>
</li>
</ol>

<p>No other identifiers are reserved.</p>

<p>Applications shall not declare or define identifiers with the same name as an identifier reserved in the same context. Since
macro names are replaced whenever found, independent of scope and name space, macro names matching any of the reserved identifier
names shall not be defined by an application if any associated header is included.</p>

<p>Except that the effect of each inclusion of <a href="../basedefs/assert.h.html"><i>&lt;assert.h&gt;</i></a> depends on the
definition of NDEBUG, headers may be included in any order, and each may be included more than once in a given scope, with no
difference in effect from that of being included only once.</p>

<p>If used, the application shall ensure that a header is included outside of any external declaration or definition, and it shall
be first included before the first reference to any type or macro it defines, or to any function or object it declares. However, if
an identifier is declared or defined in more than one header, the second and subsequent associated headers may be included after
the initial reference to the identifier. Prior to the inclusion of a header, the application shall not define any macros with names
lexically identical to symbols defined by that header.</p>


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