* translate-c: Use [N:0] arrays when initializer is a string literal
Translate incomplete arrays as [N:0] when initialized by a string literal.
This preserves a bit more of the type information from the original C program.
Fixes#8215
Fixes#2820
After reading the source code, the first two bytes are inspected, and
if they correspond to a UTF-16 BOM in little-endian order, the source
code is converted to UTF-8.
Given a pointer operand `ptr` and a signed integer operand `idx`
`ptr + idx` and `idx + ptr` -> ptr + @bitCast(usize, @intCast(isize, idx))
`ptr - idx` -> ptr - @bitCast(usize, @intCast(isize, idx))
Thanks @LemonBoy for pointing out that we can take advantage of wraparound
to dramatically simplify the code.
* Now it supports being an lvalue (see additional lines in the test
case).
* Properly handles a pointer result location (see additional lines in
the test case that assign the result of the orelse to a variable
rather than a const).
* Properly sets the result location type when possible, so that type
inference of an `orelse` operand expression knows its result type.
We can now codegen optionals! This includes the following instructions:
- is_null
- is_null_ptr
- is_non_null
- is_non_null_ptr
- optional_payload
- optional_payload_ptr
- br_void
Also includes a test for optionals.
Add support for OffsetOfExpr that contain exactly 1 component, when that component
is a field.
For example, given:
```c
struct S {
float f;
double d;
};
struct T {
long l;
int i;
struct S s[10];
};
```
Then:
```c
offsetof(struct T, i) // supported
offsetof(struct T, s[2].d) // not supported currently
```
When two pointers are subtracted, both shall point to elements of the
same array object, or one past the last element of the array object;
the result is the difference of the subscripts of the two array elements.
The size of the result is implementation-defined, and its type
(a signed integer type) is ptrdiff_t defined in the <stddef.h> header.
If the result is not representable in an object of that type,
the behavior is undefined.
See C Standard, §6.5.6 [ISO/IEC 9899:2011]
Fixes#7216
If the type is a reference to a global declaration that has not yet
been translated we need to use the global scope for translation
so that other functions can also reference it.
All stage2 tests are passing again in this branch.
Remaining checklist for this branch:
* get the rest of the zig fmt test cases passing
- re-enable the translate-c test case that is blocking on this
* implement the 2 `@panic(TODO)`'s in parse.zig
* use fn_proto not fn_decl for extern function declarations
