- VA_START(ap, var) va_start(ap, var) va_start(ap)
-
- Note that it is safe to write "void foo();" indicating a function
- with no return value, in all K+R compilers we have been able to test.
-
- For declaring functions with prototypes, we also provide these:
-
- PARAMS ((prototype))
- -- for functions which take a fixed number of arguments. Use this
- when declaring the function. When defining the function, write a
- K+R style argument list. For example:
-
- char *strcpy PARAMS ((char *dest, char *source));
- ...
- char *
- strcpy (dest, source)
- char *dest;
- char *source;
- { ... }
-
-
- VPARAMS ((prototype, ...))
- -- for functions which take a variable number of arguments. Use
- PARAMS to declare the function, VPARAMS to define it. For example:
-
- int printf PARAMS ((const char *format, ...));
- ...
- int
- printf VPARAMS ((const char *format, ...))
- {
- ...
- }
-
- For writing functions which take variable numbers of arguments, we
- also provide the VA_OPEN, VA_CLOSE, and VA_FIXEDARG macros. These
- hide the differences between K+R <varargs.h> and C89 <stdarg.h> more
- thoroughly than the simple VA_START() macro mentioned above.
-
- VA_OPEN and VA_CLOSE are used *instead of* va_start and va_end.
- Immediately after VA_OPEN, put a sequence of VA_FIXEDARG calls
- corresponding to the list of fixed arguments. Then use va_arg
- normally to get the variable arguments, or pass your va_list object
- around. You do not declare the va_list yourself; VA_OPEN does it
- for you.
-
- Here is a complete example:
-
- int
- printf VPARAMS ((const char *format, ...))
- {
- int result;
-
- VA_OPEN (ap, format);
- VA_FIXEDARG (ap, const char *, format);
-
- result = vfprintf (stdout, format, ap);
- VA_CLOSE (ap);
-
- return result;
- }
-
-
- You can declare variables either before or after the VA_OPEN,
- VA_FIXEDARG sequence. Also, VA_OPEN and VA_CLOSE are the beginning
- and end of a block. They must appear at the same nesting level,
- and any variables declared after VA_OPEN go out of scope at
- VA_CLOSE. Unfortunately, with a K+R compiler, that includes the
- argument list. You can have multiple instances of VA_OPEN/VA_CLOSE
- pairs in a single function in case you need to traverse the
- argument list more than once.