Print name of caller function

Question

I found __FUNCTION__ macro that will give the name of currently executing function, But is there any macro available to print the name of parent function (a function that invoked currently running function) ?

void print_error_message(const char *msg) { printf("%s : %s\n",__FUNCTION__,msg); } int main() { print_error_message("failed to connect"); return 0; }

The above program will give output :

print_error_message : failed to connect

But what I actually required is

main : failed to connect

because main() invoked print_error_message()

I don't want to pass one more argument to function print_error_message() like print_error_message(__FUNCTION__, msg), what I am expecting is a similar macro or function to retrieve the name of the caller function.

you can try with this stackoverflow.com/questions/16100090/… — Jahangir
– Jahangir, Commented Nov 26, 2019 at 11:20
Note that the standard name is __func__, which is a pre-defined identifier (see C11 §6.4.2.2 Predefined identifiers). The names __FUNCTION__ and __PRETTY_FUNCTION__ are GCC extensions. See What are the differences between __PRETTY_FUNCTION__, __FUNCTION__ and __func__? — Jonathan Leffler
– Jonathan Leffler, Commented Nov 26, 2019 at 11:49
Additionally, the GCC documentation on function names as strings notes: _ These identifiers are variables, not preprocessor macros, and may not be used to initialize char arrays or be concatenated with string literals._ — Jonathan Leffler
– Jonathan Leffler, Commented Nov 26, 2019 at 11:55

Some programmer dude · Accepted Answer · 2019-11-26 11:23:49Z

There's no standard way to get the name from the call-stack, and if debug information is stripped or otherwise unavailable there's possible no way at all to get the name.

As a simple workround, you could use macros:

#define print_error_message(msg) actual_print_error_message(__FUNCTION__, (msg)) void actual_print_error_message(const char *func, const char *msg) { printf("%s : %s\n",func,msg); }

Note that __FUNCTION__ is not standard C, it's an extension. For standards-compliance use the C99 special predefined variable __func__.

Paul Ogilvie · Accepted Answer · 2019-11-26 11:21:39Z

You could let the caller pass its function name as a parameter. For example:

void print_error_message(const char *msg, const char *caller) { printf("%s : %s\n",caller,msg); } int main() { print_error_message("failed to connect", __FUNCTION__); return 0; }

Afshin · Accepted Answer · 2019-11-26 11:12:29Z

1

No, it is not available and it is not possible.

Because value of a macro like __FUNCTION__ is calculated in preprocessing phase and what you want to do is not possible in that phase.

answered Nov 26, 2019 at 11:12

Afshin

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4 Comments

Ajith C Narayanan Over a year ago

But I hope there may any library functions that can do this job

Jonathan Leffler Over a year ago

Actually, the preprocessor doesn't know what a function is. so __FUNCTION__ is not handled by the preprocessor.

Afshin Over a year ago

@JonathanLeffler ? then what phase convert it into function name?

Jonathan Leffler Over a year ago

The compiler proper. It knows what functions are.

alk · Accepted Answer · 2019-12-05 09:52:05Z

I don't want to pass one more argument to function [...] I am expecting is a similar macro or function to retrieve the name of the caller function.

This does not exist, at least not as part of the C standard.

On Linux GCC provides the capability to pull backtrace info. Perhaps this helps you.

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