error out when repr(align) exceeds COFF limit

compiler/rustc_error_codes/src/error_codes/E0806.md

@@ -0,0 +1,12 @@
+The value of `N` that was specified for `repr(align(N))` was greater than the
+PE-COFF limit (8192 bytes).
+
+Erroneous code example:
+
+```ignore (fails only on PE-COFF targets)
+#[repr(align(16384))] // error: alignment must not be greater than 8192 bytes
+                      // for COFF targets
+enum Foo {
+    Bar(u64),
+}
+```

compiler/rustc_error_codes/src/lib.rs

@@ -548,6 +548,7 @@ E0802: 0802,
 E0803: 0803,
 E0804: 0804,
 E0805: 0805,
+E0806: 0806,
         );
     )
 }

compiler/rustc_passes/messages.ftl

@@ -583,6 +583,9 @@ passes_remove_fields =
      *[other] fields
     }
 
+passes_repr_align_greater_than_coff_max =
+    alignment must not be greater than 8192 bytes for COFF targets
+
 passes_repr_align_greater_than_target_max =
     alignment must not be greater than `isize::MAX` bytes
     .note = `isize::MAX` is {$size} for the current target

compiler/rustc_passes/src/check_attr.rs

@@ -36,13 +36,18 @@ use rustc_session::lint::builtin::{
 };
 use rustc_session::parse::feature_err;
 use rustc_span::{BytePos, DUMMY_SP, Span, Symbol, edition, kw, sym};
+use rustc_target::spec::BinaryFormat;
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::infer::{TyCtxtInferExt, ValuePairs};
 use rustc_trait_selection::traits::ObligationCtxt;
 use tracing::debug;
 
 use crate::{errors, fluent_generated as fluent};
 
+// Max alignment supported for PE-COFF binary format.
+// See https://learn.microsoft.com/en-us/cpp/cpp/align-cpp?view=msvc-170
+const COFF_MAX_ALIGN_BYTES: u64 = 0x2000;
+
 #[derive(LintDiagnostic)]
 #[diag(passes_diagnostic_diagnostic_on_unimplemented_only_for_traits)]
 struct DiagnosticOnUnimplementedOnlyForTraits;
@@ -2171,6 +2176,12 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
     }
 
     fn check_align_value(&self, align: Align, span: Span) {
+        if self.tcx.sess.target.binary_format == BinaryFormat::Coff {
+            if align.bytes() > COFF_MAX_ALIGN_BYTES {
+                self.dcx().emit_err(errors::InvalidReprAlignForCoff { span });
+            }
+        }
+
         if align.bytes() > 2_u64.pow(29) {
             // for values greater than 2^29, a different error will be emitted, make sure that happens
             self.dcx().span_delayed_bug(

compiler/rustc_passes/src/errors.rs

@@ -597,6 +597,13 @@ pub(crate) struct InvalidReprAlignForTarget {
     pub size: u64,
 }
 
+#[derive(Diagnostic)]
+#[diag(passes_repr_align_greater_than_coff_max, code = E0806)]
+pub(crate) struct InvalidReprAlignForCoff {
+    #[primary_span]
+    pub span: Span,
+}
+
 #[derive(LintDiagnostic)]
 #[diag(passes_repr_conflicting, code = E0566)]
 pub(crate) struct ReprConflictingLint;

tests/ui/repr/repr-align.stderr → tests/ui/repr/repr-align.notwin.stderr

@@ -1,51 +1,75 @@
 error[E0589]: invalid `repr(align)` attribute: not an unsuffixed integer
-  --> $DIR/repr-align.rs:3:14
+  --> $DIR/repr-align.rs:8:14
    |
 LL | #[repr(align(16.0))]
    |              ^^^^
 
 error[E0589]: invalid `repr(align)` attribute: not a power of two
-  --> $DIR/repr-align.rs:6:14
+  --> $DIR/repr-align.rs:11:14
    |
 LL | #[repr(align(15))]
    |              ^^
 
 error[E0589]: invalid `repr(align)` attribute: larger than 2^29
-  --> $DIR/repr-align.rs:9:14
+  --> $DIR/repr-align.rs:14:14
    |
 LL | #[repr(align(4294967296))]
    |              ^^^^^^^^^^
 
 error[E0589]: invalid `repr(align)` attribute: not a power of two
-  --> $DIR/repr-align.rs:15:14
+  --> $DIR/repr-align.rs:21:14
    |
 LL | #[repr(align(0))]
    |              ^
 
 error[E0589]: invalid `repr(align)` attribute: not an unsuffixed integer
-  --> $DIR/repr-align.rs:18:14
+  --> $DIR/repr-align.rs:27:14
    |
 LL | #[repr(align(16.0))]
    |              ^^^^
 
 error[E0589]: invalid `repr(align)` attribute: not a power of two
-  --> $DIR/repr-align.rs:21:14
+  --> $DIR/repr-align.rs:30:14
    |
 LL | #[repr(align(15))]
    |              ^^
 
 error[E0589]: invalid `repr(align)` attribute: larger than 2^29
-  --> $DIR/repr-align.rs:24:14
+  --> $DIR/repr-align.rs:33:14
    |
 LL | #[repr(align(4294967296))]
    |              ^^^^^^^^^^
 
 error[E0589]: invalid `repr(align)` attribute: not a power of two
-  --> $DIR/repr-align.rs:30:14
+  --> $DIR/repr-align.rs:40:14
    |
 LL | #[repr(align(0))]
    |              ^
 
-error: aborting due to 8 previous errors
+error[E0589]: invalid alignment value: not an unsuffixed integer
+  --> $DIR/repr-align.rs:46:9
+   |
+LL | #[align(16.0)]
+   |         ^^^^
+
+error[E0589]: invalid alignment value: not a power of two
+  --> $DIR/repr-align.rs:49:9
+   |
+LL | #[align(15)]
+   |         ^^
+
+error[E0589]: invalid alignment value: larger than 2^29
+  --> $DIR/repr-align.rs:52:9
+   |
+LL | #[align(4294967296)]
+   |         ^^^^^^^^^^
+
+error[E0589]: invalid alignment value: not a power of two
+  --> $DIR/repr-align.rs:59:9
+   |
+LL | #[align(0)]
+   |         ^
+
+error: aborting due to 12 previous errors
 
 For more information about this error, try `rustc --explain E0589`.

tests/ui/repr/repr-align.rs

@@ -1,33 +1,65 @@
+//@ revisions: win notwin
+//@[win] only-windows
+//@[notwin] ignore-windows
+
+#![feature(fn_align)]
 #![allow(dead_code)]
 
-#[repr(align(16.0))] //~ ERROR: invalid `repr(align)` attribute: not an unsuffixed integer
+#[repr(align(16.0))] //[notwin,win]~ ERROR: invalid `repr(align)` attribute: not an unsuffixed integer
 struct S0(i32);
 
-#[repr(align(15))] //~ ERROR: invalid `repr(align)` attribute: not a power of two
+#[repr(align(15))] //[notwin,win]~ ERROR: invalid `repr(align)` attribute: not a power of two
 struct S1(i32);
 
-#[repr(align(4294967296))] //~ ERROR: invalid `repr(align)` attribute: larger than 2^29
+#[repr(align(4294967296))] //[notwin,win]~ ERROR: invalid `repr(align)` attribute: larger than 2^29
 struct S2(i32);
 
-#[repr(align(536870912))] // ok: this is the largest accepted alignment
+#[repr(align(536870912))] //[win]~ ERROR: alignment must not be greater than 8192 bytes for COFF targets
+                          // notwin: this is the largest accepted alignment
 struct S3(i32);
 
-#[repr(align(0))] //~ ERROR: invalid `repr(align)` attribute: not a power of two
+#[repr(align(0))] //[notwin,win]~ ERROR: invalid `repr(align)` attribute: not a power of two
 struct S4(i32);
 
-#[repr(align(16.0))] //~ ERROR: invalid `repr(align)` attribute: not an unsuffixed integer
+#[repr(align(16384))]  //[win]~ ERROR: alignment must not be greater than 8192 bytes for COFF targets
+struct S5(i32);
+
+#[repr(align(16.0))] //[notwin,win]~ ERROR: invalid `repr(align)` attribute: not an unsuffixed integer
 enum E0 { A, B }
 
-#[repr(align(15))] //~ ERROR: invalid `repr(align)` attribute: not a power of two
+#[repr(align(15))] //[notwin,win]~ ERROR: invalid `repr(align)` attribute: not a power of two
 enum E1 { A, B }
 
-#[repr(align(4294967296))] //~ ERROR: invalid `repr(align)` attribute: larger than 2^29
+#[repr(align(4294967296))] //[notwin,win]~ ERROR: invalid `repr(align)` attribute: larger than 2^29
 enum E2 { A, B }
 
-#[repr(align(536870912))] // ok: this is the largest accepted alignment
+#[repr(align(536870912))] //[win]~ ERROR: alignment must not be greater than 8192 bytes for COFF targets
+                          // notwin: this is the largest accepted alignment
 enum E3 { A, B }
 
-#[repr(align(0))] //~ ERROR: invalid `repr(align)` attribute: not a power of two
+#[repr(align(0))] //[notwin,win]~ ERROR: invalid `repr(align)` attribute: not a power of two
 enum E4 { A, B }
 
+#[repr(align(16384))]  //[win]~ ERROR: alignment must not be greater than 8192 bytes for COFF targets
+enum E5 { A, B }
+
+#[align(16.0)] //[notwin,win]~ ERROR: invalid alignment value: not an unsuffixed integer
+fn f0() {}
+
+#[align(15)] //[notwin,win]~ ERROR: invalid alignment value: not a power of two
+fn f1() {}
+
+#[align(4294967296)] //[notwin,win]~ ERROR: alignment value: larger than 2^29
+fn f2() {}
+
+#[align(536870912)] //[win]~ ERROR: alignment must not be greater than 8192 bytes for COFF targets
+                          // notwin: this is the largest accepted alignment
+fn f3() {}
+
+#[align(0)] //[notwin,win]~ ERROR: alignment value: not a power of two
+fn f4() {}
+
+#[align(16384)]  //[win]~ ERROR: alignment must not be greater than 8192 bytes for COFF targets
+fn f5() {}
+
 fn main() {}

tests/ui/repr/repr-align.win.stderr

@@ -0,0 +1,112 @@
+error[E0589]: invalid `repr(align)` attribute: not an unsuffixed integer
+  --> $DIR/repr-align.rs:8:14
+   |
+LL | #[repr(align(16.0))]
+   |              ^^^^
+
+error[E0589]: invalid `repr(align)` attribute: not a power of two
+  --> $DIR/repr-align.rs:11:14
+   |
+LL | #[repr(align(15))]
+   |              ^^
+
+error[E0589]: invalid `repr(align)` attribute: larger than 2^29
+  --> $DIR/repr-align.rs:14:14
+   |
+LL | #[repr(align(4294967296))]
+   |              ^^^^^^^^^^
+
+error[E0589]: invalid `repr(align)` attribute: not a power of two
+  --> $DIR/repr-align.rs:21:14
+   |
+LL | #[repr(align(0))]
+   |              ^
+
+error[E0589]: invalid `repr(align)` attribute: not an unsuffixed integer
+  --> $DIR/repr-align.rs:27:14
+   |
+LL | #[repr(align(16.0))]
+   |              ^^^^
+
+error[E0589]: invalid `repr(align)` attribute: not a power of two
+  --> $DIR/repr-align.rs:30:14
+   |
+LL | #[repr(align(15))]
+   |              ^^
+
+error[E0589]: invalid `repr(align)` attribute: larger than 2^29
+  --> $DIR/repr-align.rs:33:14
+   |
+LL | #[repr(align(4294967296))]
+   |              ^^^^^^^^^^
+
+error[E0589]: invalid `repr(align)` attribute: not a power of two
+  --> $DIR/repr-align.rs:40:14
+   |
+LL | #[repr(align(0))]
+   |              ^
+
+error[E0589]: invalid alignment value: not an unsuffixed integer
+  --> $DIR/repr-align.rs:46:9
+   |
+LL | #[align(16.0)]
+   |         ^^^^
+
+error[E0589]: invalid alignment value: not a power of two
+  --> $DIR/repr-align.rs:49:9
+   |
+LL | #[align(15)]
+   |         ^^
+
+error[E0589]: invalid alignment value: larger than 2^29
+  --> $DIR/repr-align.rs:52:9
+   |
+LL | #[align(4294967296)]
+   |         ^^^^^^^^^^
+
+error[E0589]: invalid alignment value: not a power of two
+  --> $DIR/repr-align.rs:59:9
+   |
+LL | #[align(0)]
+   |         ^
+
+error[E0806]: alignment must not be greater than 8192 bytes for COFF targets
+  --> $DIR/repr-align.rs:17:8
+   |
+LL | #[repr(align(536870912))]
+   |        ^^^^^^^^^^^^^^^^
+
+error[E0806]: alignment must not be greater than 8192 bytes for COFF targets
+  --> $DIR/repr-align.rs:24:8
+   |
+LL | #[repr(align(16384))]
+   |        ^^^^^^^^^^^^
+
+error[E0806]: alignment must not be greater than 8192 bytes for COFF targets
+  --> $DIR/repr-align.rs:36:8
+   |
+LL | #[repr(align(536870912))]
+   |        ^^^^^^^^^^^^^^^^
+
+error[E0806]: alignment must not be greater than 8192 bytes for COFF targets
+  --> $DIR/repr-align.rs:43:8
+   |
+LL | #[repr(align(16384))]
+   |        ^^^^^^^^^^^^
+
+error[E0806]: alignment must not be greater than 8192 bytes for COFF targets
+  --> $DIR/repr-align.rs:55:1
+   |
+LL | #[align(536870912)]
+   | ^^^^^^^^^^^^^^^^^^^
+
+error[E0806]: alignment must not be greater than 8192 bytes for COFF targets
+  --> $DIR/repr-align.rs:62:1
+   |
+LL | #[align(16384)]
+   | ^^^^^^^^^^^^^^^
+
+error: aborting due to 18 previous errors
+
+Some errors have detailed explanations: E0589, E0806.
+For more information about an error, try `rustc --explain E0589`.