Warning: may be used uninitialized in this function - c

Question

Hitting below warning with new gcc version 6.X
Warning: 'temp' may be used uninitialized in this function [-Wmaybe-uninitialized]
Code:-
int temp;
if (logcat (MSPRO_P->regs[test],
byte, &temp, test) == FALSE){
memErrorMsgHistoryVa (MSPRO_MEMP, "Invalid Data Count 0 value");
MSPRO_P->flashCmdError = TRUE;
}

Answer 1

gcc isn't supposed to warn about passing a pointer to an uninitialized variable to a function it doesn't know anything about (the assumption is that the function will initialize it). So I'm pretty sure that gcc knows things about logcat and the uninitialized use is detected in there. Maybe it got inlined or such.
Example:
$ cat > foo.c
static int
bar(int *a)
{
return *a + *a;
}
int
foo(void)
{
int x;
int y = bar(&x);
return x + y;
}
$ cc -Wall -c foo.c
$
Here, despite it being blindingly obvious to humans, gcc doesn't actually know what happens inside the function bar. So no warning.
Let's help gcc to understand what's going on:
$ cc -O1 -Wall -c foo.c
foo.c: In function ‘foo’:
foo.c:4:12: warning: ‘x’ is used uninitialized in this function [-Wuninitialized]
return *a + *a;
~~~^~~~
foo.c:10:6: note: ‘x’ was declared here
int x;
^
$
Just turning on optimization helped gcc to see what's going on (probably some inlining happened).
From the minimal piece of code you've shown and the warning message, where it looks like you cut out the bit that actually tells you exactly where in your code the problem happens, I conclude that the problem is in your logcat function.

Answer 2

temp is uninitialized after int temp;.
logcat (MSPRO_P->regs[test], byte, &temp, test)
Since a pointer to temp is passed to the function, we, as programmers can guess that this function is supposed to initialize temp. But that is very difficult, if not impossible, for the compiler to assert with absolute certainity, specially when that function is in separate translation unit. From compilers perspective, there is no easy way to tell whether logcat will write to *temp or read it first in uninitialized state. And that's why the warning.
The easiest way to get rid of this warning is assign some initial value to temp, like:
int temp = 0