DPRINTF: Debug Printing in a C Program
This page shows a simple way to output debugging info in an ANSI C program that can be easily turned off.
Test Code | Debug vs Release build | dprintf.h Source code | Contact us
Test Code
Just include dprintf.h in your source code (see below) and use the DPRINTF*() functions to output debugging info.
This will display the debugging output in a Debug build but never display it in a Release build.
There is an option to turn off the debugging output in Debug mode, too.
/* dprintf_test.c */
#include <stdio.h>
#include "dprintf.h"
int main(void) {
int a, b;
const unsigned char bytes[] = { 0xde, 0xad, 0xbe, 0xef, 0x01, 0x02 };
printf("Hello world! This always prints.\n");
DPRINTF0("Debugging DPRINTF is active...\n");
DPRINTF1("Type=%s\n", "string");
a = 42; b = 666;
DPRINTF2("a=%d b=%d\n", a, b);
DPRBYTESMSG("bytes=", bytes, sizeof(bytes));
printf("ALL DONE.\n");
return 0;
}
In a Debug build, this outputs all the debugging info
Hello world! This always prints. Debugging DPRINTF is active... Type=string a=42 b=666 bytes=deadbeef0102 ALL DONE.
But in a Release build, all the DPRINTF statements are ignored.
Hello world! This always prints. ALL DONE.In fact, in release mode there is no extra penalty for these DPRINTF statements - they have no effect on the run time.
Strict argument count
The DPRINTFn() macros are strict in the number of arguments to be provided following the format string.
You must have exactly
n parameters.
So, for example, if you use the DPRINTF2() macro you must have exactly two parameters, i.e. in this case a and b
DPRINTF2("a=%d b=%d\n", a, b);
This is a good thing. It prevents you providing the wrong number of arguments. If you use the DPRINTF2() macro but only provide, say, one argument, you will get a compile error.
DPRINTF2("a=%d b=%d\n", a); // Error: only one argument, need two
// warning C4003: not enough actual parameters for macro 'DPRINTF2'
Think what would happen if you use the standard printf function with the wrong number of arguments!
printf("a=%d b=%d\n", a); // !!!
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