Fix minor unused/uninitialized warnings from GCC 12.3.0

[earlephilhower]

Decorate an unused parameter in the timer API and fill in all structure elements in a PIO API call that generate warnings under GCC 12.

Fixes #1785

[peterharperuk]

Looks good

[kilograham]

what is the warning what version of the compiler?

[earlephilhower]

arm-none-eabi-gcc (GCC) 12.3.0 using -Wall -Wextra

[kilograham]

Can you give the full output off gcc --version and/or say where you got it.

I'm tempted not to fix this as this is a compiler bug (and the fix is ugly/brittle), but if i can actually get an exact compiler which has this problem, i can see if it supports suppressing the warning

[earlephilhower]

I don't think this is a compiler issue so much as a C vs. C++ issue.

In C++ {0} will only set the 1st member of the structure to 0 because it's taking that as a positional initializer. In C, IIRC, {0} will effectively bzero the struct, which might be where the confusion is stemming from. You can include the SDK headers in C++ code, and when that happens the warning pops up.

This is with plain Ubuntu 20.04 GCC 9, not even the ARM x-compiler using a simple example to avoid a bunch of -Is. Just a struct with >1 member being set to {0}.

earle@amd:~/Arduino/hardware/pico/rp2040$ gcc --version
gcc (Ubuntu 9.4.0-1ubuntu1~20.04.2) 9.4.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

earle@amd:~/Arduino/hardware/pico/rp2040$ cat a.c
#include <stdio.h>
struct t {
    int a;
    int b;
};
void dummy() {
    struct t a = {0};
    printf("%d\n", a.b);
}
earle@amd:~/Arduino/hardware/pico/rp2040$ cp a.c a.cpp
earle@amd:~/Arduino/hardware/pico/rp2040$ gcc -Wall -Wextra -c  a.c
<note no warnings>
earle@amd:~/Arduino/hardware/pico/rp2040$ g++ -Wall -Wextra -c  a.c
a.c: In function ‘void dummy()’:
a.c:7:20: warning: missing initializer for member ‘t::b’ [-Wmissing-field-initializers]
    7 |     struct t a = {0};
      |       

(for completeness I see I used .c and not .cpp in the g++ line, so here that is, too:

earle@amd:~/Arduino/hardware/pico/rp2040$ g++ -Wall -Wextra -c  a.cpp
a.cpp: In function ‘void dummy()’:
a.cpp:7:20: warning: missing initializer for member ‘t::b’ [-Wmissing-field-initializers]
    7 |     struct t a = {0};
      |                    ^

and for completeness, because the SDK includes are extern "C"'d, that doesn't affect the compilation, only the name mangling:

earle@amd:~/Arduino/hardware/pico/rp2040$ cat a.cpp
#include <stdio.h>
extern "C" {
struct t {
    int a;
    int b;
};
void dummy() {
    struct t a = {0};
    printf("%d\n", a.b);
}
}
earle@amd:~/Arduino/hardware/pico/rp2040$ g++ -Wall -Wextra -c  a.cpp
a.cpp: In function ‘void dummy()’:
a.cpp:8:20: warning: missing initializer for member ‘t::b’ [-Wmissing-field-initializers]
    8 |     struct t a = {0};
      |                    ^

[kilograham]

An ok - I had wondered if this was a c++ thing - the {0} is valid C but had seen reports of some versions (albeit old) reporting that exact message