Auto merge of #110807 - petrochenkov:strictflavor, r=lqd,wesleywiser

linker: Report linker flavors incompatible with the current target

The linker flavor is checked for target compatibility even if linker is never used (e.g. we are producing a rlib).
If it causes trouble, we can move the check to `link.rs` so it will run if the linker (flavor) is actually used.

And also feature gate explicitly specifying linker flavors for tier 3 targets.

The next step is supporting all the internal linker flavors in user-visible interfaces (command line and json).

4 files changed, 33 insertions, 1 deletions

diff --git a/compiler/rustc_session/messages.ftl b/compiler/rustc_session/messages.ftl
index 5a0b8f9f73c..4897bd8d5da 100644
--- a/compiler/rustc_session/messages.ftl
+++ b/compiler/rustc_session/messages.ftl
@@ -27,6 +27,10 @@ session_feature_gate_error = {$explain}
 session_file_is_not_writeable = output file {$file} is not writeable -- check its permissions
 
 session_hexadecimal_float_literal_not_supported = hexadecimal float literal is not supported
+
+session_incompatible_linker_flavor = linker flavor `{$flavor}` is incompatible with the current target
+    .note = compatible flavors are: {$compatible_list}
+
 session_incorrect_cgu_reuse_type =
     CGU-reuse for `{$cgu_user_name}` is `{$actual_reuse}` but should be {$at_least ->
     [one] {"at least "}
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index 6c8c8e484f9..0ce83e79097 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -12,7 +12,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 
 use rustc_data_structures::stable_hasher::{StableOrd, ToStableHashKey};
 use rustc_target::abi::Align;
-use rustc_target::spec::{PanicStrategy, SanitizerSet, SplitDebuginfo};
+use rustc_target::spec::{LinkerFlavorCli, PanicStrategy, SanitizerSet, SplitDebuginfo};
 use rustc_target::spec::{Target, TargetTriple, TargetWarnings, TARGETS};
 
 use crate::parse::{CrateCheckConfig, CrateConfig};
@@ -2525,6 +2525,19 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
         }
     }
 
+    if let Some(flavor) = cg.linker_flavor {
+        if matches!(flavor, LinkerFlavorCli::BpfLinker | LinkerFlavorCli::PtxLinker)
+            && !nightly_options::is_unstable_enabled(matches)
+        {
+            let msg = format!(
+                "linker flavor `{}` is unstable, `-Z unstable-options` \
+                 flag must also be passed to explicitly use it",
+                flavor.desc()
+            );
+            early_error(error_format, msg);
+        }
+    }
+
     let prints = collect_print_requests(&mut cg, &mut unstable_opts, matches, error_format);
 
     let cg = cg;
diff --git a/compiler/rustc_session/src/errors.rs b/compiler/rustc_session/src/errors.rs
index 546c0fa8e03..4a3e668da11 100644
--- a/compiler/rustc_session/src/errors.rs
+++ b/compiler/rustc_session/src/errors.rs
@@ -422,3 +422,11 @@ pub fn report_lit_error(sess: &ParseSess, err: LitError, lit: token::Lit, span:
 pub struct OptimisationFuelExhausted {
     pub msg: String,
 }
+
+#[derive(Diagnostic)]
+#[diag(session_incompatible_linker_flavor)]
+#[note]
+pub struct IncompatibleLinkerFlavor {
+    pub flavor: &'static str,
+    pub compatible_list: String,
+}
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index bbe52dbced0..1eb54cee5a1 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -1675,6 +1675,13 @@ fn validate_commandline_args_with_session_available(sess: &Session) {
     if sess.opts.unstable_opts.instrument_xray.is_some() && !sess.target.options.supports_xray {
         sess.emit_err(errors::InstrumentationNotSupported { us: "XRay".to_string() });
     }
+
+    if let Some(flavor) = sess.opts.cg.linker_flavor {
+        if let Some(compatible_list) = sess.target.linker_flavor.check_compatibility(flavor) {
+            let flavor = flavor.desc();
+            sess.emit_err(errors::IncompatibleLinkerFlavor { flavor, compatible_list });
+        }
+    }
 }
 
 /// Holds data on the current incremental compilation session, if there is one.