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-rw-r--r--compiler/rustc_ast_lowering/src/asm.rs1
-rw-r--r--compiler/rustc_codegen_ssa/src/back/link.rs3
-rw-r--r--compiler/rustc_codegen_ssa/src/mir/naked_asm.rs50
-rw-r--r--compiler/rustc_error_messages/src/lib.rs6
-rw-r--r--compiler/rustc_hir/src/hir.rs11
-rw-r--r--compiler/rustc_hir_analysis/src/collect.rs11
-rw-r--r--compiler/rustc_interface/src/interface.rs6
-rw-r--r--compiler/rustc_interface/src/tests.rs4
-rw-r--r--compiler/rustc_metadata/src/rmeta/mod.rs3
-rw-r--r--compiler/rustc_middle/src/query/mod.rs4
-rw-r--r--compiler/rustc_middle/src/ty/parameterized.rs2
-rw-r--r--compiler/rustc_session/src/config.rs4
-rw-r--r--compiler/rustc_session/src/filesearch.rs48
-rw-r--r--compiler/rustc_session/src/options.rs2
-rw-r--r--compiler/rustc_session/src/session.rs3
15 files changed, 97 insertions, 61 deletions
diff --git a/compiler/rustc_ast_lowering/src/asm.rs b/compiler/rustc_ast_lowering/src/asm.rs
index 87af7959a88..65784af92c7 100644
--- a/compiler/rustc_ast_lowering/src/asm.rs
+++ b/compiler/rustc_ast_lowering/src/asm.rs
@@ -38,6 +38,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         }
         if let Some(asm_arch) = asm_arch {
             // Inline assembly is currently only stable for these architectures.
+            // (See also compiletest's `has_asm_support`.)
             let is_stable = matches!(
                 asm_arch,
                 asm::InlineAsmArch::X86
diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
index 0ac0ad46295..ea961f222db 100644
--- a/compiler/rustc_codegen_ssa/src/back/link.rs
+++ b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -1288,8 +1288,7 @@ fn link_sanitizer_runtime(
         if path.exists() {
             sess.target_tlib_path.dir.clone()
         } else {
-            let default_sysroot =
-                filesearch::get_or_default_sysroot().expect("Failed finding sysroot");
+            let default_sysroot = filesearch::get_or_default_sysroot();
             let default_tlib =
                 filesearch::make_target_lib_path(&default_sysroot, sess.opts.target_triple.tuple());
             default_tlib
diff --git a/compiler/rustc_codegen_ssa/src/mir/naked_asm.rs b/compiler/rustc_codegen_ssa/src/mir/naked_asm.rs
index 676cd6d2477..bc9cde1b2a1 100644
--- a/compiler/rustc_codegen_ssa/src/mir/naked_asm.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/naked_asm.rs
@@ -125,7 +125,8 @@ fn prefix_and_suffix<'tcx>(
     // the alignment from a `#[repr(align(<n>))]` is used if it specifies a higher alignment.
     // if no alignment is specified, an alignment of 4 bytes is used.
     let min_function_alignment = tcx.sess.opts.unstable_opts.min_function_alignment;
-    let align = Ord::max(min_function_alignment, attrs.alignment).map(|a| a.bytes()).unwrap_or(4);
+    let align_bytes =
+        Ord::max(min_function_alignment, attrs.alignment).map(|a| a.bytes()).unwrap_or(4);
 
     // In particular, `.arm` can also be written `.code 32` and `.thumb` as `.code 16`.
     let (arch_prefix, arch_suffix) = if is_arm {
@@ -157,12 +158,16 @@ fn prefix_and_suffix<'tcx>(
             }
             Linkage::LinkOnceAny | Linkage::LinkOnceODR | Linkage::WeakAny | Linkage::WeakODR => {
                 match asm_binary_format {
-                    BinaryFormat::Elf
-                    | BinaryFormat::Coff
-                    | BinaryFormat::Wasm
-                    | BinaryFormat::Xcoff => {
+                    BinaryFormat::Elf | BinaryFormat::Coff | BinaryFormat::Wasm => {
                         writeln!(w, ".weak {asm_name}")?;
                     }
+                    BinaryFormat::Xcoff => {
+                        // FIXME: there is currently no way of defining a weak symbol in inline assembly
+                        // for AIX. See https://github.com/llvm/llvm-project/issues/130269
+                        emit_fatal(
+                            "cannot create weak symbols from inline assembly for this target",
+                        )
+                    }
                     BinaryFormat::MachO => {
                         writeln!(w, ".globl {asm_name}")?;
                         writeln!(w, ".weak_definition {asm_name}")?;
@@ -189,7 +194,7 @@ fn prefix_and_suffix<'tcx>(
     let mut begin = String::new();
     let mut end = String::new();
     match asm_binary_format {
-        BinaryFormat::Elf | BinaryFormat::Xcoff => {
+        BinaryFormat::Elf => {
             let section = link_section.unwrap_or(format!(".text.{asm_name}"));
 
             let progbits = match is_arm {
@@ -203,7 +208,7 @@ fn prefix_and_suffix<'tcx>(
             };
 
             writeln!(begin, ".pushsection {section},\"ax\", {progbits}").unwrap();
-            writeln!(begin, ".balign {align}").unwrap();
+            writeln!(begin, ".balign {align_bytes}").unwrap();
             write_linkage(&mut begin).unwrap();
             if let Visibility::Hidden = item_data.visibility {
                 writeln!(begin, ".hidden {asm_name}").unwrap();
@@ -224,7 +229,7 @@ fn prefix_and_suffix<'tcx>(
         BinaryFormat::MachO => {
             let section = link_section.unwrap_or("__TEXT,__text".to_string());
             writeln!(begin, ".pushsection {},regular,pure_instructions", section).unwrap();
-            writeln!(begin, ".balign {align}").unwrap();
+            writeln!(begin, ".balign {align_bytes}").unwrap();
             write_linkage(&mut begin).unwrap();
             if let Visibility::Hidden = item_data.visibility {
                 writeln!(begin, ".private_extern {asm_name}").unwrap();
@@ -240,7 +245,7 @@ fn prefix_and_suffix<'tcx>(
         BinaryFormat::Coff => {
             let section = link_section.unwrap_or(format!(".text.{asm_name}"));
             writeln!(begin, ".pushsection {},\"xr\"", section).unwrap();
-            writeln!(begin, ".balign {align}").unwrap();
+            writeln!(begin, ".balign {align_bytes}").unwrap();
             write_linkage(&mut begin).unwrap();
             writeln!(begin, ".def {asm_name}").unwrap();
             writeln!(begin, ".scl 2").unwrap();
@@ -279,6 +284,33 @@ fn prefix_and_suffix<'tcx>(
             // .size is ignored for function symbols, so we can skip it
             writeln!(end, "end_function").unwrap();
         }
+        BinaryFormat::Xcoff => {
+            // the LLVM XCOFFAsmParser is extremely incomplete and does not implement many of the
+            // documented directives.
+            //
+            // - https://github.com/llvm/llvm-project/blob/1b25c0c4da968fe78921ce77736e5baef4db75e3/llvm/lib/MC/MCParser/XCOFFAsmParser.cpp
+            // - https://www.ibm.com/docs/en/ssw_aix_71/assembler/assembler_pdf.pdf
+            //
+            // Consequently, we try our best here but cannot do as good a job as for other binary
+            // formats.
+
+            // FIXME: start a section. `.csect` is not currently implemented in LLVM
+
+            // fun fact: according to the assembler documentation, .align takes an exponent,
+            // but LLVM only accepts powers of 2 (but does emit the exponent)
+            // so when we hand `.align 32` to LLVM, the assembly output will contain `.align 5`
+            writeln!(begin, ".align {}", align_bytes).unwrap();
+
+            write_linkage(&mut begin).unwrap();
+            if let Visibility::Hidden = item_data.visibility {
+                // FIXME apparently `.globl {asm_name}, hidden` is valid
+                // but due to limitations with `.weak` (see above) we can't really use that in general yet
+            }
+            writeln!(begin, "{asm_name}:").unwrap();
+
+            writeln!(end).unwrap();
+            // FIXME: end the section?
+        }
     }
 
     (begin, end)
diff --git a/compiler/rustc_error_messages/src/lib.rs b/compiler/rustc_error_messages/src/lib.rs
index 066546ecf74..39e78ae8841 100644
--- a/compiler/rustc_error_messages/src/lib.rs
+++ b/compiler/rustc_error_messages/src/lib.rs
@@ -106,8 +106,8 @@ impl From<Vec<FluentError>> for TranslationBundleError {
 /// (overriding any conflicting messages).
 #[instrument(level = "trace")]
 pub fn fluent_bundle(
-    mut user_provided_sysroot: Option<PathBuf>,
-    mut sysroot_candidates: Vec<PathBuf>,
+    sysroot: PathBuf,
+    sysroot_candidates: Vec<PathBuf>,
     requested_locale: Option<LanguageIdentifier>,
     additional_ftl_path: Option<&Path>,
     with_directionality_markers: bool,
@@ -141,7 +141,7 @@ pub fn fluent_bundle(
     // If the user requests the default locale then don't try to load anything.
     if let Some(requested_locale) = requested_locale {
         let mut found_resources = false;
-        for sysroot in user_provided_sysroot.iter_mut().chain(sysroot_candidates.iter_mut()) {
+        for mut sysroot in Some(sysroot).into_iter().chain(sysroot_candidates.into_iter()) {
             sysroot.push("share");
             sysroot.push("locale");
             sysroot.push(requested_locale.to_string());
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index d4dfb9f2973..5cf231d5668 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -3373,13 +3373,16 @@ pub struct OpaqueTy<'hir> {
     pub span: Span,
 }
 
-#[derive(Debug, Clone, Copy, HashStable_Generic)]
-pub enum PreciseCapturingArg<'hir> {
-    Lifetime(&'hir Lifetime),
+#[derive(Debug, Clone, Copy, HashStable_Generic, Encodable, Decodable)]
+pub enum PreciseCapturingArgKind<T, U> {
+    Lifetime(T),
     /// Non-lifetime argument (type or const)
-    Param(PreciseCapturingNonLifetimeArg),
+    Param(U),
 }
 
+pub type PreciseCapturingArg<'hir> =
+    PreciseCapturingArgKind<&'hir Lifetime, PreciseCapturingNonLifetimeArg>;
+
 impl PreciseCapturingArg<'_> {
     pub fn hir_id(self) -> HirId {
         match self {
diff --git a/compiler/rustc_hir_analysis/src/collect.rs b/compiler/rustc_hir_analysis/src/collect.rs
index cfb6cf8a287..e0e435dd6f0 100644
--- a/compiler/rustc_hir_analysis/src/collect.rs
+++ b/compiler/rustc_hir_analysis/src/collect.rs
@@ -28,7 +28,7 @@ use rustc_errors::{
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::intravisit::{self, InferKind, Visitor, VisitorExt, walk_generics};
-use rustc_hir::{self as hir, GenericParamKind, HirId, Node};
+use rustc_hir::{self as hir, GenericParamKind, HirId, Node, PreciseCapturingArgKind};
 use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
 use rustc_infer::traits::ObligationCause;
 use rustc_middle::hir::nested_filter;
@@ -1791,7 +1791,7 @@ fn opaque_ty_origin<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> hir::OpaqueT
 fn rendered_precise_capturing_args<'tcx>(
     tcx: TyCtxt<'tcx>,
     def_id: LocalDefId,
-) -> Option<&'tcx [Symbol]> {
+) -> Option<&'tcx [PreciseCapturingArgKind<Symbol, Symbol>]> {
     if let Some(ty::ImplTraitInTraitData::Trait { opaque_def_id, .. }) =
         tcx.opt_rpitit_info(def_id.to_def_id())
     {
@@ -1800,7 +1800,12 @@ fn rendered_precise_capturing_args<'tcx>(
 
     tcx.hir_node_by_def_id(def_id).expect_opaque_ty().bounds.iter().find_map(|bound| match bound {
         hir::GenericBound::Use(args, ..) => {
-            Some(&*tcx.arena.alloc_from_iter(args.iter().map(|arg| arg.name())))
+            Some(&*tcx.arena.alloc_from_iter(args.iter().map(|arg| match arg {
+                PreciseCapturingArgKind::Lifetime(_) => {
+                    PreciseCapturingArgKind::Lifetime(arg.name())
+                }
+                PreciseCapturingArgKind::Param(_) => PreciseCapturingArgKind::Param(arg.name()),
+            })))
         }
         _ => None,
     })
diff --git a/compiler/rustc_interface/src/interface.rs b/compiler/rustc_interface/src/interface.rs
index b35703d8e73..3f87b1a547b 100644
--- a/compiler/rustc_interface/src/interface.rs
+++ b/compiler/rustc_interface/src/interface.rs
@@ -18,7 +18,7 @@ use rustc_parse::parser::attr::AllowLeadingUnsafe;
 use rustc_query_impl::QueryCtxt;
 use rustc_query_system::query::print_query_stack;
 use rustc_session::config::{self, Cfg, CheckCfg, ExpectedValues, Input, OutFileName};
-use rustc_session::filesearch::{self, sysroot_candidates};
+use rustc_session::filesearch::sysroot_candidates;
 use rustc_session::parse::ParseSess;
 use rustc_session::{CompilerIO, EarlyDiagCtxt, Session, lint};
 use rustc_span::source_map::{FileLoader, RealFileLoader, SourceMapInputs};
@@ -390,7 +390,7 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
 
     crate::callbacks::setup_callbacks();
 
-    let sysroot = filesearch::materialize_sysroot(config.opts.maybe_sysroot.clone());
+    let sysroot = config.opts.sysroot.clone();
     let target = config::build_target_config(&early_dcx, &config.opts.target_triple, &sysroot);
     let file_loader = config.file_loader.unwrap_or_else(|| Box::new(RealFileLoader));
     let path_mapping = config.opts.file_path_mapping();
@@ -424,7 +424,7 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
             let temps_dir = config.opts.unstable_opts.temps_dir.as_deref().map(PathBuf::from);
 
             let bundle = match rustc_errors::fluent_bundle(
-                config.opts.maybe_sysroot.clone(),
+                config.opts.sysroot.clone(),
                 sysroot_candidates().to_vec(),
                 config.opts.unstable_opts.translate_lang.clone(),
                 config.opts.unstable_opts.translate_additional_ftl.as_deref(),
diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index aabd235bcab..b44be1710ed 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -21,7 +21,7 @@ use rustc_session::config::{
 use rustc_session::lint::Level;
 use rustc_session::search_paths::SearchPath;
 use rustc_session::utils::{CanonicalizedPath, NativeLib, NativeLibKind};
-use rustc_session::{CompilerIO, EarlyDiagCtxt, Session, build_session, filesearch, getopts};
+use rustc_session::{CompilerIO, EarlyDiagCtxt, Session, build_session, getopts};
 use rustc_span::edition::{DEFAULT_EDITION, Edition};
 use rustc_span::source_map::{RealFileLoader, SourceMapInputs};
 use rustc_span::{FileName, SourceFileHashAlgorithm, sym};
@@ -41,7 +41,7 @@ where
 
     let matches = optgroups().parse(args).unwrap();
     let sessopts = build_session_options(&mut early_dcx, &matches);
-    let sysroot = filesearch::materialize_sysroot(sessopts.maybe_sysroot.clone());
+    let sysroot = sessopts.sysroot.clone();
     let target =
         rustc_session::config::build_target_config(&early_dcx, &sessopts.target_triple, &sysroot);
     let hash_kind = sessopts.unstable_opts.src_hash_algorithm(&target);
diff --git a/compiler/rustc_metadata/src/rmeta/mod.rs b/compiler/rustc_metadata/src/rmeta/mod.rs
index 7b34e605c53..5536c93f84a 100644
--- a/compiler/rustc_metadata/src/rmeta/mod.rs
+++ b/compiler/rustc_metadata/src/rmeta/mod.rs
@@ -10,6 +10,7 @@ use rustc_abi::{FieldIdx, ReprOptions, VariantIdx};
 use rustc_ast::expand::StrippedCfgItem;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::svh::Svh;
+use rustc_hir::PreciseCapturingArgKind;
 use rustc_hir::def::{CtorKind, DefKind, DocLinkResMap};
 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, DefIndex, DefPathHash, StableCrateId};
 use rustc_hir::definitions::DefKey;
@@ -440,7 +441,7 @@ define_tables! {
     coerce_unsized_info: Table<DefIndex, LazyValue<ty::adjustment::CoerceUnsizedInfo>>,
     mir_const_qualif: Table<DefIndex, LazyValue<mir::ConstQualifs>>,
     rendered_const: Table<DefIndex, LazyValue<String>>,
-    rendered_precise_capturing_args: Table<DefIndex, LazyArray<Symbol>>,
+    rendered_precise_capturing_args: Table<DefIndex, LazyArray<PreciseCapturingArgKind<Symbol, Symbol>>>,
     asyncness: Table<DefIndex, ty::Asyncness>,
     fn_arg_names: Table<DefIndex, LazyArray<Ident>>,
     coroutine_kind: Table<DefIndex, hir::CoroutineKind>,
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 781a898a6e9..94a5a3769a3 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -25,7 +25,7 @@ use rustc_hir::def_id::{
     CrateNum, DefId, DefIdMap, LocalDefId, LocalDefIdMap, LocalDefIdSet, LocalModDefId,
 };
 use rustc_hir::lang_items::{LangItem, LanguageItems};
-use rustc_hir::{Crate, ItemLocalId, ItemLocalMap, TraitCandidate};
+use rustc_hir::{Crate, ItemLocalId, ItemLocalMap, PreciseCapturingArgKind, TraitCandidate};
 use rustc_index::IndexVec;
 use rustc_lint_defs::LintId;
 use rustc_macros::rustc_queries;
@@ -1424,7 +1424,7 @@ rustc_queries! {
     }
 
     /// Gets the rendered precise capturing args for an opaque for use in rustdoc.
-    query rendered_precise_capturing_args(def_id: DefId) -> Option<&'tcx [Symbol]> {
+    query rendered_precise_capturing_args(def_id: DefId) -> Option<&'tcx [PreciseCapturingArgKind<Symbol, Symbol>]> {
         desc { |tcx| "rendering precise capturing args for `{}`", tcx.def_path_str(def_id) }
         separate_provide_extern
     }
diff --git a/compiler/rustc_middle/src/ty/parameterized.rs b/compiler/rustc_middle/src/ty/parameterized.rs
index 71fc38cb7ed..19e2b574563 100644
--- a/compiler/rustc_middle/src/ty/parameterized.rs
+++ b/compiler/rustc_middle/src/ty/parameterized.rs
@@ -3,6 +3,7 @@ use std::hash::Hash;
 use rustc_data_structures::unord::UnordMap;
 use rustc_hir::def_id::DefIndex;
 use rustc_index::{Idx, IndexVec};
+use rustc_span::Symbol;
 
 use crate::ty;
 
@@ -96,6 +97,7 @@ trivially_parameterized_over_tcx! {
     rustc_hir::def_id::DefIndex,
     rustc_hir::definitions::DefKey,
     rustc_hir::OpaqueTyOrigin<rustc_hir::def_id::DefId>,
+    rustc_hir::PreciseCapturingArgKind<Symbol, Symbol>,
     rustc_index::bit_set::DenseBitSet<u32>,
     rustc_index::bit_set::FiniteBitSet<u32>,
     rustc_session::cstore::ForeignModule,
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index 7af221c9607..dcdb7fa9c10 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -1214,7 +1214,7 @@ impl Default for Options {
             describe_lints: false,
             output_types: OutputTypes(BTreeMap::new()),
             search_paths: vec![],
-            maybe_sysroot: None,
+            sysroot: filesearch::materialize_sysroot(None),
             target_triple: TargetTuple::from_tuple(host_tuple()),
             test: false,
             incremental: None,
@@ -2618,7 +2618,7 @@ pub fn build_session_options(early_dcx: &mut EarlyDiagCtxt, matches: &getopts::M
         describe_lints,
         output_types,
         search_paths,
-        maybe_sysroot: Some(sysroot),
+        sysroot,
         target_triple,
         test,
         incremental,
diff --git a/compiler/rustc_session/src/filesearch.rs b/compiler/rustc_session/src/filesearch.rs
index cc2decc2fe4..50f09c57107 100644
--- a/compiler/rustc_session/src/filesearch.rs
+++ b/compiler/rustc_session/src/filesearch.rs
@@ -160,8 +160,7 @@ fn current_dll_path() -> Result<PathBuf, String> {
 
 pub fn sysroot_candidates() -> SmallVec<[PathBuf; 2]> {
     let target = crate::config::host_tuple();
-    let mut sysroot_candidates: SmallVec<[PathBuf; 2]> =
-        smallvec![get_or_default_sysroot().expect("Failed finding sysroot")];
+    let mut sysroot_candidates: SmallVec<[PathBuf; 2]> = smallvec![get_or_default_sysroot()];
     let path = current_dll_path().and_then(|s| try_canonicalize(s).map_err(|e| e.to_string()));
     if let Ok(dll) = path {
         // use `parent` twice to chop off the file name and then also the
@@ -195,12 +194,12 @@ pub fn sysroot_candidates() -> SmallVec<[PathBuf; 2]> {
 /// Returns the provided sysroot or calls [`get_or_default_sysroot`] if it's none.
 /// Panics if [`get_or_default_sysroot`]  returns an error.
 pub fn materialize_sysroot(maybe_sysroot: Option<PathBuf>) -> PathBuf {
-    maybe_sysroot.unwrap_or_else(|| get_or_default_sysroot().expect("Failed finding sysroot"))
+    maybe_sysroot.unwrap_or_else(|| get_or_default_sysroot())
 }
 
 /// This function checks if sysroot is found using env::args().next(), and if it
 /// is not found, finds sysroot from current rustc_driver dll.
-pub fn get_or_default_sysroot() -> Result<PathBuf, String> {
+pub fn get_or_default_sysroot() -> PathBuf {
     // Follow symlinks. If the resolved path is relative, make it absolute.
     fn canonicalize(path: PathBuf) -> PathBuf {
         let path = try_canonicalize(&path).unwrap_or(path);
@@ -255,30 +254,25 @@ pub fn get_or_default_sysroot() -> Result<PathBuf, String> {
     // binary able to locate Rust libraries in systems using content-addressable
     // storage (CAS).
     fn from_env_args_next() -> Option<PathBuf> {
-        match env::args_os().next() {
-            Some(first_arg) => {
-                let mut p = PathBuf::from(first_arg);
-
-                // Check if sysroot is found using env::args().next() only if the rustc in argv[0]
-                // is a symlink (see #79253). We might want to change/remove it to conform with
-                // https://www.gnu.org/prep/standards/standards.html#Finding-Program-Files in the
-                // future.
-                if fs::read_link(&p).is_err() {
-                    // Path is not a symbolic link or does not exist.
-                    return None;
-                }
-
-                // Pop off `bin/rustc`, obtaining the suspected sysroot.
-                p.pop();
-                p.pop();
-                // Look for the target rustlib directory in the suspected sysroot.
-                let mut rustlib_path = rustc_target::relative_target_rustlib_path(&p, "dummy");
-                rustlib_path.pop(); // pop off the dummy target.
-                rustlib_path.exists().then_some(p)
-            }
-            None => None,
+        let mut p = PathBuf::from(env::args_os().next()?);
+
+        // Check if sysroot is found using env::args().next() only if the rustc in argv[0]
+        // is a symlink (see #79253). We might want to change/remove it to conform with
+        // https://www.gnu.org/prep/standards/standards.html#Finding-Program-Files in the
+        // future.
+        if fs::read_link(&p).is_err() {
+            // Path is not a symbolic link or does not exist.
+            return None;
         }
+
+        // Pop off `bin/rustc`, obtaining the suspected sysroot.
+        p.pop();
+        p.pop();
+        // Look for the target rustlib directory in the suspected sysroot.
+        let mut rustlib_path = rustc_target::relative_target_rustlib_path(&p, "dummy");
+        rustlib_path.pop(); // pop off the dummy target.
+        rustlib_path.exists().then_some(p)
     }
 
-    Ok(from_env_args_next().unwrap_or(default_from_rustc_driver_dll()?))
+    from_env_args_next().unwrap_or(default_from_rustc_driver_dll().expect("Failed finding sysroot"))
 }
diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index 8977365ee73..804b46a9bec 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -333,7 +333,7 @@ top_level_options!(
         output_types: OutputTypes [TRACKED],
         search_paths: Vec<SearchPath> [UNTRACKED],
         libs: Vec<NativeLib> [TRACKED],
-        maybe_sysroot: Option<PathBuf> [UNTRACKED],
+        sysroot: PathBuf [UNTRACKED],
 
         target_triple: TargetTuple [TRACKED],
 
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index bcd9a73d9d3..1c9adea281d 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -143,7 +143,6 @@ pub struct Session {
     pub target: Target,
     pub host: Target,
     pub opts: config::Options,
-    pub host_tlib_path: Arc<SearchPath>,
     pub target_tlib_path: Arc<SearchPath>,
     pub psess: ParseSess,
     pub sysroot: PathBuf,
@@ -1042,6 +1041,7 @@ pub fn build_session(
 
     let host_triple = config::host_tuple();
     let target_triple = sopts.target_triple.tuple();
+    // FIXME use host sysroot?
     let host_tlib_path = Arc::new(SearchPath::from_sysroot_and_triple(&sysroot, host_triple));
     let target_tlib_path = if host_triple == target_triple {
         // Use the same `SearchPath` if host and target triple are identical to avoid unnecessary
@@ -1070,7 +1070,6 @@ pub fn build_session(
         target,
         host,
         opts: sopts,
-        host_tlib_path,
         target_tlib_path,
         psess,
         sysroot,
generated by cgit-pink 1.4.1-3-g733a5 (git 2.37.1) at 2026-01-15 01:41:04 +0000