preprocessor and macros

[mosfet]

Hi,

I am using a macro to declare some logging functions in debug mode and
nothing in release, something like :

MYTRACE0( "dsqdqsdqds");
MYTRACE1( "%d", 10);
MYTRACE2( "var1=%d,; var2=%d", 10, 11);
....

As you can see I need to declare a macro for each parameter number.
Would 'nt be possible to declare only one macro that could handle
different number of parameters like :

MYTRACE("qsfqsfqfs");
MYTRACE("var1=%d, var2%d", var1, var2);

 

[Al]

mosfet wrote:

As you can see I need to declare a macro for each parameter number.
Would 'nt be possible to declare only one macro that could handle
different number of parameters like :

MYTRACE("qsfqsfqfs");
MYTRACE("var1=%d, var2%d", var1, var2);

This might help:

http://gcc.gnu.org/onlinedocs/cpp/Variadic-Macros.html

Cheers,
-Al-

 

[Richard Bos]

This might help:

http://gcc.gnu.org/onlinedocs/cpp/Variadic-Macros.html

Or possibly not, since it's about Ganuck, not about C.

If you have a C99 compiler, variadic macros are available. I'm not
experienced enough with them to explain all of it in one readable post,
but if you do a websearch for n1124.pdf, you can find out how the C99
Standard defines them.

Richard

 

[Pietro Cerutti]

mosfet wrote:


This might help:

http://gcc.gnu.org/onlinedocs/cpp/Variadic-Macros.html

I think the OP's requirement were to have two macros with the same name
perform different things based on the number of arguments.
This you can't achieve simply with variadic macros.

I would suggest to write a (inline) function instead.

 

[Thad Smith]

Would 'nt be possible to declare only one macro that could handle
different number of parameters like :

MYTRACE("qsfqsfqfs");
MYTRACE("var1=%d, var2%d", var1, var2);

As others have said, C99 provides a means to do this. With C90, the
solution is

#define MYTRACE(s) printf s

MYTRACE(("qsfqsfqfs"));
MYTRACE(("var1=%d, var2%d", var1, var2));

 

[Army1987]

As others have said, C99 provides a means to do this. With C90, the
solution is

#define MYTRACE(s) printf s

MYTRACE(("qsfqsfqfs"));
MYTRACE(("var1=%d, var2%d", var1, var2));

What if what he was trying to do was something like
#define MYTRACE(...) fprintf(stderr, __VA_ARGS__)
?

 

[Kenneth Brody]

What if what he was trying to do was something like
#define MYTRACE(...) fprintf(stderr, __VA_ARGS__)
?

You can use vfprintf(). (Or is this also C99-only?)

Call a wrapper function rather than printf(), and have this wrapper
pass the args to vfprintf() along with stderr.

--
+-------------------------+--------------------+-----------------------+
| Kenneth J. Brody | www.hvcomputer.com | #include |
| kenbrody/at\spamcop.net | www.fptech.com | <std_disclaimer.h> |
+-------------------------+--------------------+-----------------------+
Don't e-mail me at: <mailto:[email protected]>

 

[Army1987]

As others have said, C99 provides a means to do this. With C90, the
solution is

#define MYTRACE(s) printf s

MYTRACE(("qsfqsfqfs"));
MYTRACE(("var1=%d, var2%d", var1, var2));

What about:
#define MYTRACE printf
MYTRACE("qsfqsfqsf");
MYTRACE("var1=%d, var2%d", var1, var2);

 

[Thad Smith]

What about:
#define MYTRACE printf
MYTRACE("qsfqsfqsf");
MYTRACE("var1=%d, var2%d", var1, var2);

I omitted an earlier requirement in my post:

> I am using a macro to declare some logging functions in debug mode and
> nothing in release, something like :

The problem is redefining MYTRACE above to do nothing. Perhaps some
compilers would do a nice job with

#define MYTRACE (void)

although they might still generate storage for strings and give
warnings. Try it with you favorite compiler. What does it do?

 

[SM Ryan]

# Hi,
#
# I am using a macro to declare some logging functions in debug mode and
# nothing in release, something like :
#
# MYTRACE0( "dsqdqsdqds");
# MYTRACE1( "%d", 10);
# MYTRACE2( "var1=%d,; var2=%d", 10, 11);
# ...
#
# As you can see I need to declare a macro for each parameter number.
# Would 'nt be possible to declare only one macro that could handle
# different number of parameters like :
#
# MYTRACE("qsfqsfqfs");
# MYTRACE("var1=%d, var2%d", var1, var2);

#if tracing
#define MYTRACE (tracefile=__FILE__,traceline=__LINE__,tracef)
char *tracefile; int traceline;
void tracef(char *format,...) {
printf("trace %s[%d]: ",tracefile,traceline);
va_list argv; va_start(argv,format); vprintf(format,argv); va_end(argv);
printf("\n");
}
#else
#define MYTRACE (void)
#endif