warning: statement with no effect

[Chris Doran]

Hello,

I have a debug function of the form

----------------->
int DbgOut(int Filter, char *Format, ...);
<-----------------

which is used to provide printf() functionality in my debug builds. But in
my release builds I want all calls to DbgOut() to drop out _completely_
during preprocessing. So I have the following code in my DbgOut.h:

----------------->
#if DBGOUT
extern int DbgOut(int Filter, char *Format, ...);
#else
#define DbgOut(Filter,Format,args...) 0
#endif
<-----------------

However, compiling with DBGOUT=0 causes the following code
----------------->
1 void DumpFunction(void) {
2   if(DbgOut(1,"This returns nonzero only if filter 1 is enabled.")) {
3     DbgOut(1,"More extensive dump since I know filter 1 is enabled.");
4   }
5 }
<-----------------
to generate the "warning: statement with no effect" on line 3.
If a change my DbgOut macro to
#define DbgOut(Filter,Format,args...) (void)0
I get "error: void value not ignored as it ought to be" on line 2.

I already tried variations on
#define DbgOut(Filter,Format,args...) (1 ? (int)0:(void)0)
to no avail.

I would be satisfied with a command-line option to suppress the "warning:
statement with no effect" message, but there doesn't seem to be one. Note
that "statement with no effect" is exactly what I want. 8)

Any help would be appreciated.

Chris Doran
cdoran@icompression.com

gcc i386 version 2.91.66 19990314/Linux (egcs-1.1.2 release)

Complete test code:
----------------->
#define DBGOUT 0

#if DBGOUT
extern int DbgOut(int Filter, char *Format, ...);
#else
#define DbgOut(Filter,Format,args...) 0
#endif

void DumpFunction(void) {
  if(DbgOut(1,"This returns nonzero only if filter 1 is enabled.")) {
    DbgOut(1,"More extensive dump since I know filter 1 is enabled.");
  }
  DbgOut(2,"Another filter.");
} 
<-----------------