C Runtime API Reference

The following C runtime library calls are supported in the RTSS environment.

NOTE: You can define UNDER_RTSS_UNSUPPORTED_CRT_APIS either before rtapi.h is included or as a pre-processor definition to see what RTSS C Runtime functions have been deprecated.

NOTE: Printf requires the Microsoft C Runtime but RtPrintf does not. RtPrintf uses a RTX-provided implementation that provides a subset of the Printf functionality.

C Library Function Name	Notes	Deterministic?
_aligned_free		No
_aligned_malloc		No
_aligned_msize		No
_aligned_offset_malloc		No
_aligned_offset_realloc		No
_aligned_offset_recalloc		No
_aligned_realloc		No
_aligned_recalloc		No
abs	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
acos	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
asin	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
atan	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
atan2	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
atof	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
atoi	The call is supported as both an Rt call and as a Win32 call (for example, RtAtoi and Atoi). Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
atol	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
bsearch	Not supported in shared RTDLL.	Yes - the call is deterministic for small input sizes.
calloc	Not supported in shared RTDLL.	No
ceil	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
cos	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
cosh	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
difftime	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
div	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
exit	Not supported in shared RTDLL.	No
exp	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
fabs	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
fclose	Not supported in shared RTDLL.	No
fflush	Not supported in shared RTDLL.	No
fgets	Not supported in shared RTDLL.	No
floor	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
fmod	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
fopen	Not supported in shared RTDLL.	No
fprintf(stderr)	Not for use in an RTSS DLL. Not supported in shared RTDLL.	No
fputc	Not supported in shared RTDLL.	No
fputs	Not supported in shared RTDLL.	No
fread	Not supported in shared RTDLL.	No
free	Not supported in shared RTDLL.	No
frexp	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
fseek	Not supported in shared RTDLL.	No
ftell	Not supported in shared RTDLL.	No
fwrite	Not supported in shared RTDLL.	No
getc	Not supported in shared RTDLL.	No
isalnum	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
isalpha	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
iscntrl	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
isdigit	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
isgraph	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
islower	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
isprint	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
ispunct	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
isspace	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
isupper	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
iswalnum	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
iswalpha	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
iswascii	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
iswcntrl	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
iswctype	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
iswdigit	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
iswgraph	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
iswlower	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
iswprint	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
iswpunct	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
iswspace	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
iswupper	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
iswxdigit	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
isxdigit	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
labs	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
ldexp	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
ldiv	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
log	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
log10	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
longjmp	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
main	Not supported in shared RTDLL.	No
malloc	Not supported in shared RTDLL.	No
memchr	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
memcmp	Not supported in shared RTDLL.	Yes - the call is deterministic for small input sizes.
memcpy	Not supported in shared RTDLL.	Yes - the call is deterministic for small input sizes.
memmove	Not supported in shared RTDLL.	Yes - the call is deterministic for small input sizes.
memset	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
modf	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
perror	Not for use in an RTSS DLL. Not supported in shared RTDLL.	No
pow	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
printf	The call is supported as both an Rt call and as a Win32 call (for example, RtAtoi and Atoi). Not for use in an RTSS DLL. Not supported in shared RTDLL.	No
putc	Not supported in shared RTDLL.	No
putchar	Not supported in shared RTDLL.	No
qsort	Not supported in shared RTDLL.	Yes - the call is deterministic for small input sizes.
rand	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
realloc	Not supported in shared RTDLL.	No
rewind	Not supported in shared RTDLL.	No
setjmp	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
signal	Not supported in shared RTDLL.	No
sin	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
sinh	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
sprintf	The call is supported as both an Rt call and as a Win32 call (for example, RtAtoi and Atoi). Not for use in an RTSS DLL. Not supported in shared RTDLL.	No
sqrt	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
srand	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
sscanf	Not supported in shared RTDLL.	No
strcat	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
strchr	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
strcmp	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
strcpy	Not supported in shared RTDLL.	Yes - the call is deterministic for small input sizes.
strcspn	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
strerror	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
strlen	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
strncat	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
strncmp	Not supported in shared RTDLL.	Yes - the call is deterministic for small input sizes.
strncpy	Not supported in shared RTDLL.	Yes - the call is deterministic for small input sizes.
strpbrk	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
strrchr	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
strspn	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
strstr	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
strtod	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
strtok	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
strtol	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
strtoul	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
swprintf	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
tan	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
tanh	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
tolower	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
toupper	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
towlower	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
towupper	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
ungetc	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
va_start	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
vsprintf	Not for use in an RTSS DLL. Not supported in shared RTDLL.	No
wcscat	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
wcschr	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
wcscmp	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
wcscpy	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
wcscspn	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
wcsftime	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
wcslen	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
wcsncat	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
wcsncmp	Not supported in shared RTDLL.	Yes - the call is deterministic for small input sizes.
wcsncpy	Not supported in shared RTDLL.	Yes - the call is deterministic for small input sizes.
wcspbrk	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
wcsrchr	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
wcsspn	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
wcsstr	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
wcstod	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
wcstok	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
wcstol	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
wcstoul	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
wmain	Not supported in shared RTDLL.	No
wprintf	The call is supported as both an Rt call and as a Win32 call (for example, RtAtoi and Atoi). Not for use in an RTSS DLL. Not supported in shared RTDLL.	No
wtof	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
wtoi	The call is supported as both an Rt call and as a Win32 call (for example, RtAtoi and Atoi). Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
wtol	Not supported in shared RTDLL.	Yes - the elapsed time for the call is less than 5 microseconds.
_controlfp	Not supported in shared RTDLL.	No
_fpreset	Not supported in shared RTDLL.	No

NOTE: The RTX C Runtime function exit() terminates a program execution and RTX closes all open files when the program ends; the value argument of exit() is not returned to the caller.

Using Visual Studio 2015 and 2013 with C Runtime

The following C runtime library calls supported in the RTSS environment have been deprecated in Visual Studio. The function that replaces them is listed in the right column.

Deprecated Function	New Function
controlfp	_controlfp_s
fopen	fopen_s
fprintf (stderr)	fprintf_s
memcpy	memcpy_s
memmove	memmove_s
sprintf	sprintf_s
strcat	strcat_s
strcpy	strcpy_s
strerror	strerror_s
strncpy	strncpy_s
strtok	strtok_s
swprintf	swprintf_s
vsprintf	vsprintf_s
vswprintf	vswprintf_s
wcscat	wcscat_s
wcscpy	wcscpy_s
wcsncpy	wcsncpy_s
wcstok	wcstok_s

NOTE: Visual Studio optimization may sometimes optimize code into C Runtime functions. This may require previous RTSS Release applications that did not link to C Runtime to now link to C Runtime.