Keil Software — Cx51 Compiler User’s Guide |
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Appendix A. Differences from ANSI C
The Cx51 compiler differs in only a few aspects from the ANSI C Standard. |
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These differences can be grouped into compiler-related differences and |
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library-related differences. |
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Compiler-related Differences
Wide Characters
Wide 16-bit characters are not supported by Cx51. ANSI provides wide characters for future support of an international character set.
Recursive Function Calls
Recursive function calls are not supported by default. Functions that are recursive must be declared using the reentrant function attribute. Reentrant functions can be called recursively because the local data and parameters are stored in a reentrant stack. In comparison, functions which are not declared using the reentrant attribute use static memory segments for the local data of the function. A recursive call to these functions overwrites the local data of the prior function call instance.
Library-related Differences
The ANSI C Standard Library includes a vast number of routines, most of which are included in Cx51. Many, however, are not applicable to an embedded application and are excluded from the Cx51 library.
The following ANSI Standard library routines are included in the Cx51 library:
abs |
cosh |
isdigit |
acos |
exp |
isgraph |
asin |
fabs |
islower |
atan |
floor |
isprint |
atan2 |
fmod |
ispunct |
atof |
free |
isspace |
atoi |
getchar |
isupper |
atol |
gets |
isxdigit |
calloc |
isalnum |
labs |
ceil |
isalpha |
log |
cos |
iscntrl |
log10 |
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Appendix A. Differences from ANSI C |
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longjmp |
sin |
strrchr |
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malloc |
sinh |
strspn |
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memchr |
sprintf |
strstr |
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memcmp |
sqrt |
strtod |
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memcpy |
srand |
strtol |
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memmove |
sscanf |
strtoul |
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memset |
strcat |
tan |
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modf |
strchr |
tanh |
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pow |
strcmp |
tolower |
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printf |
strcpy |
toupper |
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putchar |
strcspn |
va_arg |
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puts |
strlen |
va_end |
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rand |
strncat |
va_start |
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realloc |
strncmp |
vprintf |
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scanf |
strncpy |
vsprintf |
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setjmp |
strpbrk |
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The following ANSI Standard library routines are not included in the Cx51 |
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library: |
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abort |
freopen |
remove |
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asctime |
frexp |
rename |
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atexit |
fscanf |
rewind |
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bsearch |
fseek |
setbuf |
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clearerr |
fsetpos |
setlocale |
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clock |
ftell |
setvbuf |
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ctime |
fwrite |
signal |
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difftime |
getc |
strcoll |
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div |
getenv |
strerror |
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exit |
gmtime |
strftime |
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fclose |
ldexp |
strtok |
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feof |
ldiv |
strxfrm |
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ferror |
localeconv |
system |
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fflush |
localtime |
time |
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fgetc |
mblen |
tmpfile |
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fgetpos |
mbstowcs |
tmpnam |
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fgets |
mbtowc |
ungetc |
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fopen |
mktime |
vfprintf |
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fprintf |
perror |
wcstombs |
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fputc |
putc |
wctomb |
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fputs |
qsort |
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fread |
raise |
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Appendix A. Differences from ANSI C |
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