Auto merge of #111248 - Dylan-DPC:rollup-lbp0ui3, r=Dylan-DPC

Rollup of 6 pull requests

Successful merges:

 - #103056 (Fix `checked_{add,sub}_duration` incorrectly returning `None` when `other` has more than `i64::MAX` seconds)
 - #108801 (Implement RFC 3348, `c"foo"` literals)
 - #110773 (Reduce MIR dump file count for MIR-opt tests)
 - #110876 (Added default target cpu to `--print target-cpus` output and updated docs)
 - #111068 (Improve check-cfg implementation)
 - #111238 (btree_map: `Cursor{,Mut}::peek_prev` must agree)

Failed merges:

 - #110694 (Implement builtin # syntax and use it for offset_of!(...))

r? `@ghost`
`@rustbot` modify labels: rollup

compiler/rustc_ast/src/ast.rs

@@ -1821,6 +1821,8 @@ pub enum LitKind {
     /// A byte string (`b"foo"`). Not stored as a symbol because it might be
     /// non-utf8, and symbols only allow utf8 strings.
     ByteStr(Lrc<[u8]>, StrStyle),
+    /// A C String (`c"foo"`). Guaranteed to only have `\0` at the end.
+    CStr(Lrc<[u8]>, StrStyle),
     /// A byte char (`b'f'`).
     Byte(u8),
     /// A character literal (`'a'`).
@@ -1875,6 +1877,7 @@ impl LitKind {
             // unsuffixed variants
             LitKind::Str(..)
             | LitKind::ByteStr(..)
+            | LitKind::CStr(..)
             | LitKind::Byte(..)
             | LitKind::Char(..)
             | LitKind::Int(_, LitIntType::Unsuffixed)

compiler/rustc_ast/src/token.rs

@@ -74,6 +74,8 @@ pub enum LitKind {
     StrRaw(u8), // raw string delimited by `n` hash symbols
     ByteStr,
     ByteStrRaw(u8), // raw byte string delimited by `n` hash symbols
+    CStr,
+    CStrRaw(u8),
     Err,
 }
 
@@ -141,6 +143,10 @@ impl fmt::Display for Lit {
                 delim = "#".repeat(n as usize),
                 string = symbol
             )?,
+            CStr => write!(f, "c\"{symbol}\"")?,
+            CStrRaw(n) => {
+                write!(f, "cr{delim}\"{symbol}\"{delim}", delim = "#".repeat(n as usize))?
+            }
             Integer | Float | Bool | Err => write!(f, "{symbol}")?,
         }
 
@@ -170,6 +176,7 @@ impl LitKind {
             Float => "float",
             Str | StrRaw(..) => "string",
             ByteStr | ByteStrRaw(..) => "byte string",
+            CStr | CStrRaw(..) => "C string",
             Err => "error",
         }
     }

compiler/rustc_ast/src/util/literal.rs

@@ -2,9 +2,13 @@
 
 use crate::ast::{self, LitKind, MetaItemLit, StrStyle};
 use crate::token::{self, Token};
-use rustc_lexer::unescape::{byte_from_char, unescape_byte, unescape_char, unescape_literal, Mode};
+use rustc_lexer::unescape::{
+    byte_from_char, unescape_byte, unescape_c_string, unescape_char, unescape_literal, CStrUnit,
+    Mode,
+};
 use rustc_span::symbol::{kw, sym, Symbol};
 use rustc_span::Span;
+use std::ops::Range;
 use std::{ascii, fmt, str};
 
 // Escapes a string, represented as a symbol. Reuses the original symbol,
@@ -35,6 +39,7 @@ pub enum LitError {
     InvalidFloatSuffix,
     NonDecimalFloat(u32),
     IntTooLarge(u32),
+    NulInCStr(Range<usize>),
 }
 
 impl LitKind {
@@ -158,6 +163,52 @@ impl LitKind {
 
                 LitKind::ByteStr(bytes.into(), StrStyle::Raw(n))
             }
+            token::CStr => {
+                let s = symbol.as_str();
+                let mut buf = Vec::with_capacity(s.len());
+                let mut error = Ok(());
+                unescape_c_string(s, Mode::CStr, &mut |span, c| match c {
+                    Ok(CStrUnit::Byte(0) | CStrUnit::Char('\0')) => {
+                        error = Err(LitError::NulInCStr(span));
+                    }
+                    Ok(CStrUnit::Byte(b)) => buf.push(b),
+                    Ok(CStrUnit::Char(c)) if c.len_utf8() == 1 => buf.push(c as u8),
+                    Ok(CStrUnit::Char(c)) => {
+                        buf.extend_from_slice(c.encode_utf8(&mut [0; 4]).as_bytes())
+                    }
+                    Err(err) => {
+                        if err.is_fatal() {
+                            error = Err(LitError::LexerError);
+                        }
+                    }
+                });
+                error?;
+                buf.push(0);
+                LitKind::CStr(buf.into(), StrStyle::Cooked)
+            }
+            token::CStrRaw(n) => {
+                let s = symbol.as_str();
+                let mut buf = Vec::with_capacity(s.len());
+                let mut error = Ok(());
+                unescape_c_string(s, Mode::RawCStr, &mut |span, c| match c {
+                    Ok(CStrUnit::Byte(0) | CStrUnit::Char('\0')) => {
+                        error = Err(LitError::NulInCStr(span));
+                    }
+                    Ok(CStrUnit::Byte(b)) => buf.push(b),
+                    Ok(CStrUnit::Char(c)) if c.len_utf8() == 1 => buf.push(c as u8),
+                    Ok(CStrUnit::Char(c)) => {
+                        buf.extend_from_slice(c.encode_utf8(&mut [0; 4]).as_bytes())
+                    }
+                    Err(err) => {
+                        if err.is_fatal() {
+                            error = Err(LitError::LexerError);
+                        }
+                    }
+                });
+                error?;
+                buf.push(0);
+                LitKind::CStr(buf.into(), StrStyle::Raw(n))
+            }
             token::Err => LitKind::Err,
         })
     }
@@ -191,6 +242,14 @@ impl fmt::Display for LitKind {
                     string = symbol
                 )?;
             }
+            LitKind::CStr(ref bytes, StrStyle::Cooked) => {
+                write!(f, "c\"{}\"", escape_byte_str_symbol(bytes))?
+            }
+            LitKind::CStr(ref bytes, StrStyle::Raw(n)) => {
+                // This can only be valid UTF-8.
+                let symbol = str::from_utf8(bytes).unwrap();
+                write!(f, "cr{delim}\"{symbol}\"{delim}", delim = "#".repeat(n as usize),)?;
+            }
             LitKind::Int(n, ty) => {
                 write!(f, "{n}")?;
                 match ty {
@@ -237,6 +296,8 @@ impl MetaItemLit {
             LitKind::Str(_, ast::StrStyle::Raw(n)) => token::StrRaw(n),
             LitKind::ByteStr(_, ast::StrStyle::Cooked) => token::ByteStr,
             LitKind::ByteStr(_, ast::StrStyle::Raw(n)) => token::ByteStrRaw(n),
+            LitKind::CStr(_, ast::StrStyle::Cooked) => token::CStr,
+            LitKind::CStr(_, ast::StrStyle::Raw(n)) => token::CStrRaw(n),
             LitKind::Byte(_) => token::Byte,
             LitKind::Char(_) => token::Char,
             LitKind::Int(..) => token::Integer,

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -572,6 +572,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session) {
             }
         };
     }
+    gate_all!(c_str_literals, "`c\"..\"` literals are experimental");
     gate_all!(
         if_let_guard,
         "`if let` guards are experimental",

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -210,6 +210,10 @@ pub fn literal_to_string(lit: token::Lit) -> String {
         token::ByteStrRaw(n) => {
             format!("br{delim}\"{string}\"{delim}", delim = "#".repeat(n as usize), string = symbol)
         }
+        token::CStr => format!("c\"{symbol}\""),
+        token::CStrRaw(n) => {
+            format!("cr{delim}\"{symbol}\"{delim}", delim = "#".repeat(n as usize))
+        }
         token::Integer | token::Float | token::Bool | token::Err => symbol.to_string(),
     };
 

compiler/rustc_attr/src/builtin.rs

@@ -5,6 +5,7 @@ use rustc_ast::{Attribute, LitKind, MetaItem, MetaItemKind, MetaItemLit, NestedM
 use rustc_ast_pretty::pprust;
 use rustc_feature::{find_gated_cfg, is_builtin_attr_name, Features, GatedCfg};
 use rustc_macros::HashStable_Generic;
+use rustc_session::config::ExpectedValues;
 use rustc_session::lint::builtin::UNEXPECTED_CFGS;
 use rustc_session::lint::BuiltinLintDiagnostics;
 use rustc_session::parse::{feature_err, ParseSess};
@@ -581,32 +582,32 @@ pub fn cfg_matches(
 ) -> bool {
     eval_condition(cfg, sess, features, &mut |cfg| {
         try_gate_cfg(cfg.name, cfg.span, sess, features);
-        if let Some(names_valid) = &sess.check_config.names_valid {
-            if !names_valid.contains(&cfg.name) {
+        match sess.check_config.expecteds.get(&cfg.name) {
+            Some(ExpectedValues::Some(values)) if !values.contains(&cfg.value) => {
                 sess.buffer_lint_with_diagnostic(
                     UNEXPECTED_CFGS,
                     cfg.span,
                     lint_node_id,
-                    "unexpected `cfg` condition name",
-                    BuiltinLintDiagnostics::UnexpectedCfg((cfg.name, cfg.name_span), None),
+                    "unexpected `cfg` condition value",
+                    BuiltinLintDiagnostics::UnexpectedCfgValue(
+                        (cfg.name, cfg.name_span),
+                        cfg.value.map(|v| (v, cfg.value_span.unwrap())),
+                    ),
                 );
             }
-        }
-        if let Some(value) = cfg.value {
-            if let Some(values) = &sess.check_config.values_valid.get(&cfg.name) {
-                if !values.contains(&value) {
-                    sess.buffer_lint_with_diagnostic(
-                        UNEXPECTED_CFGS,
-                        cfg.span,
-                        lint_node_id,
-                        "unexpected `cfg` condition value",
-                        BuiltinLintDiagnostics::UnexpectedCfg(
-                            (cfg.name, cfg.name_span),
-                            cfg.value_span.map(|vs| (value, vs)),
-                        ),
-                    );
-                }
+            None if sess.check_config.exhaustive_names => {
+                sess.buffer_lint_with_diagnostic(
+                    UNEXPECTED_CFGS,
+                    cfg.span,
+                    lint_node_id,
+                    "unexpected `cfg` condition name",
+                    BuiltinLintDiagnostics::UnexpectedCfgName(
+                        (cfg.name, cfg.name_span),
+                        cfg.value.map(|v| (v, cfg.value_span.unwrap())),
+                    ),
+                );
             }
+            _ => { /* not unexpected */ }
         }
         sess.config.contains(&(cfg.name, cfg.value))
     })

compiler/rustc_builtin_macros/src/concat.rs

@@ -32,6 +32,10 @@ pub fn expand_concat(
                 Ok(ast::LitKind::Bool(b)) => {
                     accumulator.push_str(&b.to_string());
                 }
+                Ok(ast::LitKind::CStr(..)) => {
+                    cx.span_err(e.span, "cannot concatenate a C string literal");
+                    has_errors = true;
+                }
                 Ok(ast::LitKind::Byte(..) | ast::LitKind::ByteStr(..)) => {
                     cx.emit_err(errors::ConcatBytestr { span: e.span });
                     has_errors = true;

compiler/rustc_builtin_macros/src/concat_bytes.rs

@@ -18,6 +18,11 @@ fn invalid_type_err(
     };
     let snippet = cx.sess.source_map().span_to_snippet(span).ok();
     match ast::LitKind::from_token_lit(token_lit) {
+        Ok(ast::LitKind::CStr(_, _)) => {
+            // FIXME(c_str_literals): should concatenation of C string literals
+            // include the null bytes in the end?
+            cx.span_err(span, "cannot concatenate C string literals");
+        }
         Ok(ast::LitKind::Char(_)) => {
             let sugg =
                 snippet.map(|snippet| ConcatBytesInvalidSuggestion::CharLit { span, snippet });

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -2249,7 +2249,7 @@ extern "C" {
 
     pub fn LLVMRustHasFeature(T: &TargetMachine, s: *const c_char) -> bool;
 
-    pub fn LLVMRustPrintTargetCPUs(T: &TargetMachine);
+    pub fn LLVMRustPrintTargetCPUs(T: &TargetMachine, cpu: *const c_char);
     pub fn LLVMRustGetTargetFeaturesCount(T: &TargetMachine) -> size_t;
     pub fn LLVMRustGetTargetFeature(
         T: &TargetMachine,

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -329,7 +329,14 @@ pub(crate) fn print(req: PrintRequest, sess: &Session) {
     require_inited();
     let tm = create_informational_target_machine(sess);
     match req {
-        PrintRequest::TargetCPUs => unsafe { llvm::LLVMRustPrintTargetCPUs(tm) },
+        PrintRequest::TargetCPUs => {
+            // SAFETY generate a C compatible string from a byte slice to pass
+            // the target CPU name into LLVM, the lifetime of the reference is
+            // at least as long as the C function
+            let cpu_cstring = CString::new(handle_native(sess.target.cpu.as_ref()))
+                .unwrap_or_else(|e| bug!("failed to convert to cstring: {}", e));
+            unsafe { llvm::LLVMRustPrintTargetCPUs(tm, cpu_cstring.as_ptr()) };
+        }
         PrintRequest::TargetFeatures => print_target_features(sess, tm),
         _ => bug!("rustc_codegen_llvm can't handle print request: {:?}", req),
     }

compiler/rustc_expand/src/proc_macro_server.rs

@@ -61,6 +61,8 @@ impl FromInternal<token::LitKind> for LitKind {
             token::StrRaw(n) => LitKind::StrRaw(n),
             token::ByteStr => LitKind::ByteStr,
             token::ByteStrRaw(n) => LitKind::ByteStrRaw(n),
+            token::CStr => LitKind::CStr,
+            token::CStrRaw(n) => LitKind::CStrRaw(n),
             token::Err => LitKind::Err,
             token::Bool => unreachable!(),
         }
@@ -78,6 +80,8 @@ impl ToInternal<token::LitKind> for LitKind {
             LitKind::StrRaw(n) => token::StrRaw(n),
             LitKind::ByteStr => token::ByteStr,
             LitKind::ByteStrRaw(n) => token::ByteStrRaw(n),
+            LitKind::CStr => token::CStr,
+            LitKind::CStrRaw(n) => token::CStrRaw(n),
             LitKind::Err => token::Err,
         }
     }
@@ -436,6 +440,8 @@ impl server::FreeFunctions for Rustc<'_, '_> {
                 | token::LitKind::StrRaw(_)
                 | token::LitKind::ByteStr
                 | token::LitKind::ByteStrRaw(_)
+                | token::LitKind::CStr
+                | token::LitKind::CStrRaw(_)
                 | token::LitKind::Err => return Err(()),
                 token::LitKind::Integer | token::LitKind::Float => {}
             }

compiler/rustc_feature/src/active.rs

@@ -313,6 +313,8 @@ declare_features! (
     (active, async_closure, "1.37.0", Some(62290), None),
     /// Allows async functions to be declared, implemented, and used in traits.
     (active, async_fn_in_trait, "1.66.0", Some(91611), None),
+    /// Allows `c"foo"` literals.
+    (active, c_str_literals, "CURRENT_RUSTC_VERSION", Some(105723), None),
     /// Treat `extern "C"` function as nounwind.
     (active, c_unwind, "1.52.0", Some(74990), None),
     /// Allows using C-variadics.

compiler/rustc_hir/src/lang_items.rs

@@ -333,6 +333,7 @@ language_item_table! {
     RangeTo,                 sym::RangeTo,             range_to_struct,            Target::Struct,         GenericRequirement::None;
 
     String,                  sym::String,              string,                     Target::Struct,         GenericRequirement::None;
+    CStr,                    sym::CStr,                c_str,                      Target::Struct,         GenericRequirement::None;
 }
 
 pub enum GenericRequirement {

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -1300,6 +1300,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 opt_ty.unwrap_or_else(|| self.next_float_var())
             }
             ast::LitKind::Bool(_) => tcx.types.bool,
+            ast::LitKind::CStr(_, _) => tcx.mk_imm_ref(
+                tcx.lifetimes.re_static,
+                tcx.type_of(tcx.require_lang_item(hir::LangItem::CStr, Some(lit.span)))
+                    .skip_binder(),
+            ),
             ast::LitKind::Err => tcx.ty_error_misc(),
         }
     }