The following functions are compatible with ANSI:
clearerr, fclose, feof, ferror, fflush, fgetc, fgetpos, fgets, fopen, fprintf, fputc, fputs, fread, freopen, fscanf, fseek, fsetpos, ftell, fwrite, getc, getchar, gets, perror, printf, putc, putchar, puts, remove, rename, rewind, scanf, setbuf, setvbuf, sprintf, sscanf, tmpfile, tmpnam, vfprintf, ungetc, vprintf, vsprintf,
memchr, memcmp, memcpy, memmove, memset, strcat, strchr, strcmp, strcoll, strcpy, strcspn, strerror, strlen, strncat, strncmp, strncpy, strpbrk, strrchr, strspn, strstr, strtok, strxfrm
abort, abs, assert, atexit, atof, atoi, atol, bsearch, calloc, div, exit, free, getenv, labs, ldiv, longjmp, malloc, mblen, mbstowcs, mbtowc, qsort, rand, realloc, setjmp, srand, strtod, strtol, strtoul, system, wcstombs, wctomb
asctime, gmtime, localtime, time, clock, ctime, difftime, mktime, strftime
raise, signal
isalnum, isalpha, iscntrl, isdigit, isgraph, islower, isprint, ispunct, isspace, isupper, isxdigit, tolower, toupper
acos, asin, atan, atan2, ceil, cos, cosh, exp, fabs, floor, fmod, frexp, ldexp, log, log10, modf, pow, sin, sinh, sqrt, tan, tanh
localeconv, setlocale, va_arg, va_end, va_start