Add PWR079: Avoid undefined behavior due to uninitialized variables

[alvrogd]

Add entry and benchmark for a new check. My results:

$ lscpu
  Model name:             13th Gen Intel(R) Core(TM) i7-13700H

$ gcc --version                            
gcc (Debian 12.2.0-14) 12.2.0

$ gfortran --version                                                 
GNU Fortran (Debian 12.2.0-14) 12.2.0

$ ./run-benchmarks.py --check PWR079
------------------------------------------------------------------
Benchmark                        Time             CPU   Iterations
------------------------------------------------------------------
PWR079 C Example               556 us          556 us         1256
PWR079 C Improved              558 us          558 us         1256
PWR079 Fortran Example         556 us          556 us         1260
PWR079 Fortran Improved        555 us          555 us         1257

This new check would also resolve #39. Nullifying pointers upon creation is suggested as part of the check.

[daniel-otero]

LGTM

[daniel-otero]

Maybe avoid using sum here to remove ambiguity with the sum of the sum_array function (same in the Fortran example).

[igarcia0]

Agreed.

Suggested change

	double sum = sum_array(array, 5);
	printf("Sum is: %f\n", sum);
	printf("Sum is: %f\n", sum_array(array, 5));

[alvrogd]

to remove ambiguity

Good catch! Done in both the C and Fortran code examples.

[inaki-amatria]

Looks great! Good job

[igarcia0]

Looks good!

[igarcia0]

Nit:

Suggested change

	__attribute__((pure)) double sum_array(double *array, int size) {
	__attribute__((pure)) double sum_array(double *array, size_t size) {

[alvrogd]

I usually opt for int to prevent including a header, but since stdio.h is already used within this code example, fine by me! :)

[igarcia0]

Agreed.

Suggested change

	double sum = sum_array(array, 5);
	printf("Sum is: %f\n", sum);
	printf("Sum is: %f\n", sum_array(array, 5));