Skip to content

compiler: Deduplicate must_emit_unwind_tables() comments #143564

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Jul 7, 2025
Merged

compiler: Deduplicate must_emit_unwind_tables() comments #143564

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
1eff043
rustc_codegen_llvm: Remove reference to non-existing `no_landing_pads()`
Enselic Jul 7, 2025
aa364ca
compiler: Deduplicate `must_emit_unwind_tables()` comments
Enselic Jul 7, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
16 changes: 0 additions & 16 deletions compiler/rustc_codegen_llvm/src/attributes.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -370,22 +370,6 @@ pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
};
to_add.extend(inline_attr(cx, inline));

// The `uwtable` attribute according to LLVM is:
//
// This attribute indicates that the ABI being targeted requires that an
// unwind table entry be produced for this function even if we can show
// that no exceptions passes by it. This is normally the case for the
// ELF x86-64 abi, but it can be disabled for some compilation units.
//
// Typically when we're compiling with `-C panic=abort` (which implies this
// `no_landing_pads` check) we don't need `uwtable` because we can't
// generate any exceptions! On Windows, however, exceptions include other
// events such as illegal instructions, segfaults, etc. This means that on
// Windows we end up still needing the `uwtable` attribute even if the `-C
// panic=abort` flag is passed.
//
// You can also find more info on why Windows always requires uwtables here:
// https://bugzilla.mozilla.org/show_bug.cgi?id=1302078
if cx.sess().must_emit_unwind_tables() {
to_add.push(uwtable_attr(cx.llcx, cx.sess().opts.unstable_opts.use_sync_unwind));
}
Expand Down
9 changes: 8 additions & 1 deletion compiler/rustc_session/src/session.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -776,8 +776,15 @@ impl Session {

pub fn must_emit_unwind_tables(&self) -> bool {
// This is used to control the emission of the `uwtable` attribute on
// LLVM functions.
// LLVM functions. The `uwtable` attribute according to LLVM is:
//
// This attribute indicates that the ABI being targeted requires that an
// unwind table entry be produced for this function even if we can show
// that no exceptions passes by it. This is normally the case for the
// ELF x86-64 abi, but it can be disabled for some compilation units.
//
// Typically when we're compiling with `-C panic=abort` we don't need
// `uwtable` because we can't generate any exceptions!
// Unwind tables are needed when compiling with `-C panic=unwind`, but
// LLVM won't omit unwind tables unless the function is also marked as
// `nounwind`, so users are allowed to disable `uwtable` emission.
Expand Down
Loading