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More core::fmt::rt cleanup. #110766

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merged 5 commits into from
Apr 28, 2023
Merged

More core::fmt::rt cleanup. #110766

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5cf3cbf
Remove "V1" from ArgumentsV1 and FlagsV1.
m-ou-se Apr 20, 2023
0a28977
Restructure std::fmt::rt a bit.
m-ou-se Apr 24, 2023
9cc5949
Update tests.
m-ou-se Apr 20, 2023
7bae143
Update miri test.
m-ou-se Apr 24, 2023
52ff751
pub -> pub(super).
m-ou-se Apr 27, 2023
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2 changes: 1 addition & 1 deletion compiler/rustc_ast_lowering/src/format.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -327,7 +327,7 @@ fn make_format_spec<'hir>(
None => sym::Unknown,
},
);
// This needs to match `Flag` in library/core/src/fmt/mod.rs.
// This needs to match `Flag` in library/core/src/fmt/rt.rs.
let flags: u32 = ((sign == Some(FormatSign::Plus)) as u32)
| ((sign == Some(FormatSign::Minus)) as u32) << 1
| (alternate as u32) << 2
Expand Down
246 changes: 52 additions & 194 deletions library/core/src/fmt/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -251,145 +251,48 @@ impl<'a> Formatter<'a> {
}
}

// NB. Argument is essentially an optimized partially applied formatting function,
// equivalent to `exists T.(&T, fn(&T, &mut Formatter<'_>) -> Result`.

extern "C" {
type Opaque;
}

/// This struct represents the generic "argument" which is taken by the Xprintf
/// family of functions. It contains a function to format the given value. At
/// compile time it is ensured that the function and the value have the correct
/// types, and then this struct is used to canonicalize arguments to one type.
#[lang = "format_argument"]
/// This structure represents a safely precompiled version of a format string
/// and its arguments. This cannot be generated at runtime because it cannot
/// safely be done, so no constructors are given and the fields are private
/// to prevent modification.
///
/// The [`format_args!`] macro will safely create an instance of this structure.
/// The macro validates the format string at compile-time so usage of the
/// [`write()`] and [`format()`] functions can be safely performed.
///
/// You can use the `Arguments<'a>` that [`format_args!`] returns in `Debug`
/// and `Display` contexts as seen below. The example also shows that `Debug`
/// and `Display` format to the same thing: the interpolated format string
/// in `format_args!`.
///
/// ```rust
/// let debug = format!("{:?}", format_args!("{} foo {:?}", 1, 2));
/// let display = format!("{}", format_args!("{} foo {:?}", 1, 2));
/// assert_eq!("1 foo 2", display);
/// assert_eq!(display, debug);
/// ```
///
/// [`format()`]: ../../std/fmt/fn.format.html
#[lang = "format_arguments"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Copy, Clone)]
#[allow(missing_debug_implementations)]
#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
#[doc(hidden)]
pub struct Argument<'a> {
value: &'a Opaque,
formatter: fn(&Opaque, &mut Formatter<'_>) -> Result,
}

/// This struct represents the unsafety of constructing an `Arguments`.
/// It exists, rather than an unsafe function, in order to simplify the expansion
/// of `format_args!(..)` and reduce the scope of the `unsafe` block.
#[lang = "format_unsafe_arg"]
#[allow(missing_debug_implementations)]
#[doc(hidden)]
#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
pub struct UnsafeArg {
_private: (),
}

impl UnsafeArg {
/// See documentation where `UnsafeArg` is required to know when it is safe to
/// create and use `UnsafeArg`.
#[doc(hidden)]
#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
#[inline(always)]
pub unsafe fn new() -> Self {
Self { _private: () }
}
}

// This guarantees a single stable value for the function pointer associated with
// indices/counts in the formatting infrastructure.
//
// Note that a function defined as such would not be correct as functions are
// always tagged unnamed_addr with the current lowering to LLVM IR, so their
// address is not considered important to LLVM and as such the as_usize cast
// could have been miscompiled. In practice, we never call as_usize on non-usize
// containing data (as a matter of static generation of the formatting
// arguments), so this is merely an additional check.
//
// We primarily want to ensure that the function pointer at `USIZE_MARKER` has
// an address corresponding *only* to functions that also take `&usize` as their
// first argument. The read_volatile here ensures that we can safely ready out a
// usize from the passed reference and that this address does not point at a
// non-usize taking function.
#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
static USIZE_MARKER: fn(&usize, &mut Formatter<'_>) -> Result = |ptr, _| {
// SAFETY: ptr is a reference
let _v: usize = unsafe { crate::ptr::read_volatile(ptr) };
loop {}
};

macro_rules! arg_new {
($f: ident, $t: ident) => {
#[doc(hidden)]
#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
#[inline]
pub fn $f<'b, T: $t>(x: &'b T) -> Argument<'_> {
Self::new(x, $t::fmt)
}
};
}

#[rustc_diagnostic_item = "ArgumentMethods"]
impl<'a> Argument<'a> {
#[doc(hidden)]
#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
#[inline]
pub fn new<'b, T>(x: &'b T, f: fn(&T, &mut Formatter<'_>) -> Result) -> Argument<'b> {
// SAFETY: `mem::transmute(x)` is safe because
// 1. `&'b T` keeps the lifetime it originated with `'b`
// (so as to not have an unbounded lifetime)
// 2. `&'b T` and `&'b Opaque` have the same memory layout
// (when `T` is `Sized`, as it is here)
// `mem::transmute(f)` is safe since `fn(&T, &mut Formatter<'_>) -> Result`
// and `fn(&Opaque, &mut Formatter<'_>) -> Result` have the same ABI
// (as long as `T` is `Sized`)
unsafe { Argument { formatter: mem::transmute(f), value: mem::transmute(x) } }
}

arg_new!(new_display, Display);
arg_new!(new_debug, Debug);
arg_new!(new_octal, Octal);
arg_new!(new_lower_hex, LowerHex);
arg_new!(new_upper_hex, UpperHex);
arg_new!(new_pointer, Pointer);
arg_new!(new_binary, Binary);
arg_new!(new_lower_exp, LowerExp);
arg_new!(new_upper_exp, UpperExp);
pub struct Arguments<'a> {
// Format string pieces to print.
pieces: &'a [&'static str],

#[doc(hidden)]
#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
pub fn from_usize(x: &usize) -> Argument<'_> {
Argument::new(x, USIZE_MARKER)
}

fn as_usize(&self) -> Option<usize> {
// We are type punning a bit here: USIZE_MARKER only takes an &usize but
// formatter takes an &Opaque. Rust understandably doesn't think we should compare
// the function pointers if they don't have the same signature, so we cast to
// usizes to tell it that we just want to compare addresses.
if self.formatter as usize == USIZE_MARKER as usize {
// SAFETY: The `formatter` field is only set to USIZE_MARKER if
// the value is a usize, so this is safe
Some(unsafe { *(self.value as *const _ as *const usize) })
} else {
None
}
}
}
// Placeholder specs, or `None` if all specs are default (as in "{}{}").
fmt: Option<&'a [rt::Placeholder]>,

// flags available in the v1 format of format_args
#[derive(Copy, Clone)]
enum Flag {
SignPlus,
SignMinus,
Alternate,
SignAwareZeroPad,
DebugLowerHex,
DebugUpperHex,
// Dynamic arguments for interpolation, to be interleaved with string
// pieces. (Every argument is preceded by a string piece.)
args: &'a [rt::Argument<'a>],
}

/// Used by the format_args!() macro to create a fmt::Arguments object.
#[doc(hidden)]
#[unstable(feature = "fmt_internals", issue = "none")]
impl<'a> Arguments<'a> {
#[doc(hidden)]
#[inline]
#[unstable(feature = "fmt_internals", issue = "none")]
#[rustc_const_unstable(feature = "const_fmt_arguments_new", issue = "none")]
pub const fn new_const(pieces: &'a [&'static str]) -> Self {
if pieces.len() > 1 {
Expand All @@ -401,22 +304,18 @@ impl<'a> Arguments<'a> {
/// When using the format_args!() macro, this function is used to generate the
/// Arguments structure.
#[cfg(not(bootstrap))]
#[doc(hidden)]
#[inline]
#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
pub fn new_v1(pieces: &'a [&'static str], args: &'a [Argument<'a>]) -> Arguments<'a> {
pub fn new_v1(pieces: &'a [&'static str], args: &'a [rt::Argument<'a>]) -> Arguments<'a> {
if pieces.len() < args.len() || pieces.len() > args.len() + 1 {
panic!("invalid args");
}
Arguments { pieces, fmt: None, args }
}

#[cfg(bootstrap)]
#[doc(hidden)]
#[inline]
#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
#[rustc_const_unstable(feature = "const_fmt_arguments_new", issue = "none")]
pub const fn new_v1(pieces: &'a [&'static str], args: &'a [Argument<'a>]) -> Arguments<'a> {
pub const fn new_v1(pieces: &'a [&'static str], args: &'a [rt::Argument<'a>]) -> Arguments<'a> {
if pieces.len() < args.len() || pieces.len() > args.len() + 1 {
panic!("invalid args");
}
Expand All @@ -425,19 +324,17 @@ impl<'a> Arguments<'a> {

/// This function is used to specify nonstandard formatting parameters.
///
/// An `UnsafeArg` is required because the following invariants must be held
/// An `rt::UnsafeArg` is required because the following invariants must be held
/// in order for this function to be safe:
/// 1. The `pieces` slice must be at least as long as `fmt`.
/// 2. Every `rt::Placeholder::position` value within `fmt` must be a valid index of `args`.
/// 3. Every `rt::Count::Param` within `fmt` must contain a valid index of `args`.
#[doc(hidden)]
#[inline]
#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
pub fn new_v1_formatted(
pieces: &'a [&'static str],
args: &'a [Argument<'a>],
args: &'a [rt::Argument<'a>],
fmt: &'a [rt::Placeholder],
_unsafe_arg: UnsafeArg,
_unsafe_arg: rt::UnsafeArg,
) -> Arguments<'a> {
Arguments { pieces, fmt: Some(fmt), args }
}
Expand All @@ -446,9 +343,7 @@ impl<'a> Arguments<'a> {
///
/// This is intended to be used for setting initial `String` capacity
/// when using `format!`. Note: this is neither the lower nor upper bound.
#[doc(hidden)]
#[inline]
#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
pub fn estimated_capacity(&self) -> usize {
let pieces_length: usize = self.pieces.iter().map(|x| x.len()).sum();

Expand All @@ -468,43 +363,6 @@ impl<'a> Arguments<'a> {
}
}

/// This structure represents a safely precompiled version of a format string
/// and its arguments. This cannot be generated at runtime because it cannot
/// safely be done, so no constructors are given and the fields are private
/// to prevent modification.
///
/// The [`format_args!`] macro will safely create an instance of this structure.
/// The macro validates the format string at compile-time so usage of the
/// [`write()`] and [`format()`] functions can be safely performed.
///
/// You can use the `Arguments<'a>` that [`format_args!`] returns in `Debug`
/// and `Display` contexts as seen below. The example also shows that `Debug`
/// and `Display` format to the same thing: the interpolated format string
/// in `format_args!`.
///
/// ```rust
/// let debug = format!("{:?}", format_args!("{} foo {:?}", 1, 2));
/// let display = format!("{}", format_args!("{} foo {:?}", 1, 2));
/// assert_eq!("1 foo 2", display);
/// assert_eq!(display, debug);
/// ```
///
/// [`format()`]: ../../std/fmt/fn.format.html
#[lang = "format_arguments"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Copy, Clone)]
pub struct Arguments<'a> {
// Format string pieces to print.
pieces: &'a [&'static str],

// Placeholder specs, or `None` if all specs are default (as in "{}{}").
fmt: Option<&'a [rt::Placeholder]>,

// Dynamic arguments for interpolation, to be interleaved with string
// pieces. (Every argument is preceded by a string piece.)
args: &'a [Argument<'a>],
}

impl<'a> Arguments<'a> {
/// Get the formatted string, if it has no arguments to be formatted at runtime.
///
Expand Down Expand Up @@ -1244,7 +1102,7 @@ pub fn write(output: &mut dyn Write, args: Arguments<'_>) -> Result {
if !piece.is_empty() {
formatter.buf.write_str(*piece)?;
}
(arg.formatter)(arg.value, &mut formatter)?;
arg.fmt(&mut formatter)?;
idx += 1;
}
}
Expand Down Expand Up @@ -1274,7 +1132,7 @@ pub fn write(output: &mut dyn Write, args: Arguments<'_>) -> Result {
Ok(())
}

unsafe fn run(fmt: &mut Formatter<'_>, arg: &rt::Placeholder, args: &[Argument<'_>]) -> Result {
unsafe fn run(fmt: &mut Formatter<'_>, arg: &rt::Placeholder, args: &[rt::Argument<'_>]) -> Result {
fmt.fill = arg.fill;
fmt.align = arg.align;
fmt.flags = arg.flags;
Expand All @@ -1292,10 +1150,10 @@ unsafe fn run(fmt: &mut Formatter<'_>, arg: &rt::Placeholder, args: &[Argument<'
let value = unsafe { args.get_unchecked(arg.position) };

// Then actually do some printing
(value.formatter)(value.value, fmt)
value.fmt(fmt)
}

unsafe fn getcount(args: &[Argument<'_>], cnt: &rt::Count) -> Option<usize> {
unsafe fn getcount(args: &[rt::Argument<'_>], cnt: &rt::Count) -> Option<usize> {
match *cnt {
rt::Count::Is(n) => Some(n),
rt::Count::Implied => None,
Expand Down Expand Up @@ -1878,7 +1736,7 @@ impl<'a> Formatter<'a> {
#[must_use]
#[stable(feature = "fmt_flags", since = "1.5.0")]
pub fn sign_plus(&self) -> bool {
self.flags & (1 << Flag::SignPlus as u32) != 0
self.flags & (1 << rt::Flag::SignPlus as u32) != 0
}

/// Determines if the `-` flag was specified.
Expand Down Expand Up @@ -1907,7 +1765,7 @@ impl<'a> Formatter<'a> {
#[must_use]
#[stable(feature = "fmt_flags", since = "1.5.0")]
pub fn sign_minus(&self) -> bool {
self.flags & (1 << Flag::SignMinus as u32) != 0
self.flags & (1 << rt::Flag::SignMinus as u32) != 0
}

/// Determines if the `#` flag was specified.
Expand Down Expand Up @@ -1935,7 +1793,7 @@ impl<'a> Formatter<'a> {
#[must_use]
#[stable(feature = "fmt_flags", since = "1.5.0")]
pub fn alternate(&self) -> bool {
self.flags & (1 << Flag::Alternate as u32) != 0
self.flags & (1 << rt::Flag::Alternate as u32) != 0
}

/// Determines if the `0` flag was specified.
Expand All @@ -1961,17 +1819,17 @@ impl<'a> Formatter<'a> {
#[must_use]
#[stable(feature = "fmt_flags", since = "1.5.0")]
pub fn sign_aware_zero_pad(&self) -> bool {
self.flags & (1 << Flag::SignAwareZeroPad as u32) != 0
self.flags & (1 << rt::Flag::SignAwareZeroPad as u32) != 0
}

// FIXME: Decide what public API we want for these two flags.
// https://github.com/rust-lang/rust/issues/48584
fn debug_lower_hex(&self) -> bool {
self.flags & (1 << Flag::DebugLowerHex as u32) != 0
self.flags & (1 << rt::Flag::DebugLowerHex as u32) != 0
}

fn debug_upper_hex(&self) -> bool {
self.flags & (1 << Flag::DebugUpperHex as u32) != 0
self.flags & (1 << rt::Flag::DebugUpperHex as u32) != 0
}

/// Creates a [`DebugStruct`] builder designed to assist with creation of
Expand Down Expand Up @@ -2531,13 +2389,13 @@ pub(crate) fn pointer_fmt_inner(ptr_addr: usize, f: &mut Formatter<'_>) -> Resul
// or not to zero extend, and then unconditionally set it to get the
// prefix.
if f.alternate() {
f.flags |= 1 << (Flag::SignAwareZeroPad as u32);
f.flags |= 1 << (rt::Flag::SignAwareZeroPad as u32);

if f.width.is_none() {
f.width = Some((usize::BITS / 4) as usize + 2);
}
}
f.flags |= 1 << (Flag::Alternate as u32);
f.flags |= 1 << (rt::Flag::Alternate as u32);

let ret = LowerHex::fmt(&ptr_addr, f);

Expand Down
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