'va_start' used in function with fixed args - objective-c

Question

I have Logger.h with following code:
#import <Foundation/Foundation.h>
#import <asl.h>
#define LogDebug(format, ...){ \
Logger(ASL_LEVEL_DEBUG, format,##__VA_ARGS__); }
#define Logger(LEVEL,format, ...) \
LogLocal(LEVEL,format,##__VA_ARGS__);
#define LogLocal(LEVEL, format, ...) \
va_list arg_list; \
va_start(arg_list, format); \
// ...\
va_end(arg_list); \
I call log from Obj-C as:
LogDebug(#"Name is called with flag: %#", collectName ? #"YES" : #"NO");
However I get an error:
'va_start' used in function with fixed args
How to get rid of this problem?
EDIT 1:
I tried to call also: AFLogLocal(LEVEL,format,...); - same error
EDIT 2:
if I'll remove asl_log and replace with NSLog - it will work:
#define LogLocal(LEVEL,format, ...) \
NSLog((#"XXX: %s " format), __PRETTY_FUNCTION__, ##__VA_ARGS__);
EDIT 3
credits to #Amin Negm-Awad, replaced LogLocal with function in .m file as:
void LogLocal(int level, NSString *format, ...){
va_list arg_list;
va_start(arg_list, format);
va_end(arg_list);
NSString *formattedString = [[NSString alloc] initWithFormat:format arguments:arg_list];
asl_add_log_file(NULL, STDERR_FILENO);
asl_log(NULL, NULL, (level), "XXXX: %s", [formattedString UTF8String]);
}
works as expected.

Answer 1

You use macros that are expanded. But they do not create a scope or a call on expansion. It's simple text replacement.
// Somewhere in a function
void f(void)
{
…
LogDebug(#"Name is called with flag: %#", collectName ? #"YES" : #"NO");
…
}
This will expand at the end to something like this:
// Somewhere in a function
void f(void)
{
…
// LogDebug(#"Name is called with flag: %#", collectName ? #"YES" : #"NO");
va_list arg_list;
va_start(arg_list, #"Name is called with flag: %#");
// ...
va_end(arg_list);
…
}
Since f() takes no vargs, there are no vargs.
It might help to make LogLocal() a function, not a macro:
void LogLocal( int level, NSString *format, ... );
Implementation:
void LogLocal( int level, NSString *format, ... )
{
va_list arg_list;
va_start(arg_list, format);
// ...
va_end(arg_list);
}
To your Edit 2:
Yes, this works, because you do not touch the arg list, but pass the args to a function taking vargs. But you do not need that trick. Instead make LogLocal() a function and it will be called similar to NSLog() without any error.