Question on: debug printf macro

[Enrico]

Hi,

I'm writing a C program and I would like to know if the following
thing is feasable?


1) My program is made of 10 files.


2) Each module can print a debug string over the standard output. For
example:

debug_printf (MODULE_1, "The value of temperature is %d",
temperature);
debug_printf (MODULE_2, "I received the following char - %c", ch);
debug_printf (MODULE_3, "Ok, I'm done");


3) I want to be able to:

- switch off all the printf call. That means that the "debug_printf"
call must be removed by the preprocessor
- switch on selected printf call


Thanks in advance,
Enrico Migliore
--
comp.lang.c.moderated - moderation address: cl...@plethora.net -- you must
have an appropriate newsgroups line in your header for your mail to be seen,
or the newsgroup name in square brackets in the subject line. Sorry.

[fasked]

> - switch off all the printf call. That means that the "debug_printf"
> call must be removed by the preprocessor

Just make `debug_printf' an macros.

#ifdef DEBUG_LOG
#define debug_printf(module_id, fmt, ...) \
fprintf(stderr, "[module: %d]: "fmt, module_id, ##__VA_ARGS__);
#else
#define debug_printf(module_id, fmt, ...)
#endif

Define the `DEBUG_LOG' if you want to use debug logging or undef it
otherwise. In second case `debug_printf' macros will expanded as
nothing :) You can test it if you will run just only preprocessor.

> - switch on selected printf call

What do you mean by `switch on selected'? Any example please.

[Thomas Richter]

On 28.10.2011 08:59, Enrico wrote:

> 2) Each module can print a debug string over the standard output. For
> example:
>
> debug_printf (MODULE_1, "The value of temperature is %d",
> temperature);
> debug_printf (MODULE_2, "I received the following char - %c", ch);
> debug_printf (MODULE_3, "Ok, I'm done");
>
>
> 3) I want to be able to:
>
> - switch off all the printf call. That means that the "debug_printf"
> call must be removed by the preprocessor
> - switch on selected printf call

A typical solution to such problems is to define a macro that, depending
on debugging support turned on or off expands to its argument or nothing:

#ifdef DEBUG
#define D(a) a
#else
#define D(a)
#endif

Then, use the following in your program instead:

D(printf (MODULE_2, "I received the following char - %c", ch));

HTHH,
Thomas

[James Kuyper]

On 10/28/2011 02:59 AM, Enrico wrote:
> Hi,
>
> I'm writing a C program and I would like to know if the following
> thing is feasable?
>
>
> 1) My program is made of 10 files.
>
>
> 2) Each module can print a debug string over the standard output. For
> example:
>
> debug_printf (MODULE_1, "The value of temperature is %d",
> temperature);
> debug_printf (MODULE_2, "I received the following char - %c", ch);
> debug_printf (MODULE_3, "Ok, I'm done");
>
>
> 3) I want to be able to:
>
> - switch off all the printf call. That means that the "debug_printf"
> call must be removed by the preprocessor
> - switch on selected printf call

Define the actual function to be real_debug_printf().

#ifdef DEBUG_PRINTF
#define debug_printf(args) real_debug_printf(args)
#else
#define debug_printf(args)
#endif

To switch a particular call on, when all of the others are turned off by
the above method, then just add the "real_" prefix.
--
James Kuyper

[Dag-Erling Smørgrav]

Enrico <zig...@libero.it> writes:
> 2) Each module can print a debug string over the standard output. For
> example:
>
> debug_printf (MODULE_1, "The value of temperature is %d", temperature);
> debug_printf (MODULE_2, "I received the following char - %c", ch);
> debug_printf (MODULE_3, "Ok, I'm done");
>
> 3) I want to be able to:
>
> - switch off all the printf call. That means that the "debug_printf"
> call must be removed by the preprocessor
> - switch on selected printf call

Something like

int real_debug_printf(int, const char *fmt, ...);
#ifndef NDEBUG
#define debug_printf(module, ...) \
real_debug_printf((module), __VA_ARGS__)
#else
#define debug_printf(module, ...) 0
#endif

DES
--
Dag-Erling Smørgrav - d...@des.no

[Hans-Bernhard Bröker]

On 28.10.2011 08:59, Enrico wrote:

> - switch off all the printf call. That means that the "debug_printf"
> call must be removed by the preprocessor
> - switch on selected printf call

If that's what you want to do, then you cannot implement your debug
printf the way you planned. You need

DEBUG_PRINTF_MODULE1(("The value of temperature is %d", temperature));

instead, so you can then

#ifdef DEBUGGING_MODULE1
#define DEBUG_PRINTF_MODULE1(args) printf(args)
#else
#define DEBUG_PRINTF_MODULE1(args) /*nothing*/
#endif

Note that I'm assuming no C99, so you need the double () trick to feed
variable argument lists through a macro.

[Dag-Erling Smørgrav]

James Kuyper <james...@verizon.net> writes:
> #ifdef DEBUG_PRINTF
> #define debug_printf(args) real_debug_printf(args)
> #else
> #define debug_printf(args)
> #endif

That won't work. He needs a macro that takes at least two arguments:
the module ID and the format string plus zero or more substitution
parameters.

DES
--
Dag-Erling Smørgrav - d...@des.no