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Add nul-terminated filename for #[track_caller] #131828
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Original file line number | Diff line number | Diff line change |
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@@ -1,5 +1,8 @@ | ||
use crate::fmt; | ||
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#[cfg(not(bootstrap))] | ||
use crate::ffi::CStr; | ||
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/// A struct containing information about the location of a panic. | ||
/// | ||
/// This structure is created by [`PanicHookInfo::location()`] and [`PanicInfo::location()`]. | ||
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@@ -32,7 +35,11 @@ use crate::fmt; | |
#[derive(Copy, Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)] | ||
#[stable(feature = "panic_hooks", since = "1.10.0")] | ||
pub struct Location<'a> { | ||
file: &'a str, | ||
// When not bootstrapping the compiler, it is an invariant that the last byte of this string | ||
// slice is a nul-byte. | ||
// | ||
// When bootstrapping the compiler, this string may be missing the nul-terminator. | ||
file_with_nul: &'a str, | ||
line: u32, | ||
col: u32, | ||
} | ||
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@@ -127,7 +134,30 @@ impl<'a> Location<'a> { | |
#[rustc_const_stable(feature = "const_location_fields", since = "1.79.0")] | ||
#[inline] | ||
pub const fn file(&self) -> &str { | ||
self.file | ||
// String slicing in const is very hard, see: | ||
// <https://users.rust-lang.org/t/slicing-strings-in-const/119836> | ||
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let s = self.file_with_nul; | ||
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#[cfg(bootstrap)] | ||
if !matches!(s.as_bytes().last(), Some(0)) { | ||
return s; | ||
} | ||
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#[cfg(debug_assertions)] | ||
if !matches!(s.as_bytes().last(), Some(0)) { | ||
panic!("filename is not nul terminated"); | ||
} | ||
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// SAFETY: The string contains a nul-byte, so the length is at least one. | ||
let len = unsafe { s.len().unchecked_sub(1) }; | ||
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// SAFETY: `s.as_ptr()` is valid for `len+1` bytes, so it is valid for `len` bytes. | ||
let file = unsafe { core::slice::from_raw_parts(s.as_ptr(), len) }; | ||
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// SAFETY: This is valid utf-8 because the original string is valid utf-8 and the last | ||
// character was a nul-byte, so removing it does not cut a codepoint in half. | ||
unsafe { core::str::from_utf8_unchecked(file) } | ||
} | ||
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/// Returns the line number from which the panic originated. | ||
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@@ -179,24 +209,34 @@ impl<'a> Location<'a> { | |
pub const fn column(&self) -> u32 { | ||
self.col | ||
} | ||
} | ||
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#[unstable( | ||
feature = "panic_internals", | ||
reason = "internal details of the implementation of the `panic!` and related macros", | ||
issue = "none" | ||
)] | ||
impl<'a> Location<'a> { | ||
#[doc(hidden)] | ||
pub const fn internal_constructor(file: &'a str, line: u32, col: u32) -> Self { | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Note that this internal constructor does not seem to be used anymore. |
||
Location { file, line, col } | ||
/// Returns the name of the source file from which the panic originated as a nul-terminated | ||
/// string. | ||
/// | ||
/// This function is like [`Location::file`], except that it returns a nul-terminated string. It | ||
/// is mainly useful for passing the filename into C or C++ code. | ||
#[must_use] | ||
#[inline] | ||
#[unstable(feature = "panic_file_with_nul", issue = "none")] | ||
#[cfg(not(bootstrap))] | ||
pub fn file_with_nul(&self) -> &CStr { | ||
let file_with_nul = self.file_with_nul.as_bytes(); | ||
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#[cfg(debug_assertions)] | ||
if !matches!(file_with_nul.last(), Some(0)) { | ||
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|
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panic!("filename is not nul terminated"); | ||
} | ||
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// SAFETY: This struct is only ever constructed by the compiler, which always inserts a | ||
// nul-terminator in this string. | ||
unsafe { CStr::from_bytes_with_nul_unchecked(file_with_nul) } | ||
} | ||
} | ||
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#[stable(feature = "panic_hook_display", since = "1.26.0")] | ||
impl fmt::Display for Location<'_> { | ||
#[inline] | ||
fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result { | ||
write!(formatter, "{}:{}:{}", self.file, self.line, self.col) | ||
write!(formatter, "{}:{}:{}", self.file(), self.line, self.col) | ||
} | ||
} |
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Would be nice to mark the string as cstring in the compiled object files to allow the linker to deduplicate it.
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Is that done by using a different
MemoryKind
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I don't think we currently have a way to do this, but it would make sense to me to do it by adding a new
MemoryKind
and then special casing this in the codegen backends.There was a problem hiding this comment.
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I don't want to complicate this PR too much. That sounds like it could happen as a follow-up.