ignoring return value of ‘fscanf’, declared with attribute warn_unused_result

Hi,
I was wondering if don't accept return value of fscanf and fgets, can these warnings be some potentially serious problem:

warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result
warning: ignoring return value of ‘fgets’, declared with attribute warn_unused_result

Here is the code:

Code:

fscanf(modelfl,"%ld%*[^\n]\n", &model->kernel_parm.kernel_type); // model is just some realization of a structure
fgets(line,(int)ll,modelfl);

Makefile setting:

CFLAGS= $(SFLAGS) -O3 # release C-Compiler flags
LFLAGS= $(SFLAGS) -O3 # release linker flags
LIBS=-L. -lm

These warnings only occur when -O3 is specified. If nothing is specified, then there will be no warning.

Thanks in advance!

check return value of fscanf

I liked the "If I turn off warnings, I don't get warnings!" part of the post.


Quzah.

The warnings are trying to tell you that you are ignoring the error status of those two calls, i.e. you aren't checking if they succeeded.

The best solution is to check the return values like you should be doing.

You could just cast them to void:

Code:

(void) fscanf(modelfl,"%ld%*[^\n]\n", &model->kernel_parm.kernel_type); // model is just some realization of a structure
(void) fgets(line,(int)ll,modelfl);

But ideally it's a good idea to pay attention to what's being returned for the sake of error checking.


Quzah.