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Auto merge of rust-lang#118417 - anforowicz:default-hidden-visibility…
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Add unstable `-Zdefault-hidden-visibility` cmdline flag for `rustc`.

The new flag has been described in the Major Change Proposal at
rust-lang/compiler-team#656
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bors committed Dec 14, 2023
2 parents 1a8afa0 + 981c4e3 commit 9d49eb7
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Showing 10 changed files with 66 additions and 8 deletions.
2 changes: 1 addition & 1 deletion compiler/rustc_codegen_gcc/src/allocator.rs
Original file line number Diff line number Diff line change
Expand Up @@ -90,7 +90,7 @@ fn create_wrapper_function(
.collect();
let func = context.new_function(None, FunctionType::Exported, output.unwrap_or(void), &args, from_name, false);

if tcx.sess.target.options.default_hidden_visibility {
if tcx.sess.default_hidden_visibility() {
#[cfg(feature="master")]
func.add_attribute(FnAttribute::Visibility(gccjit::Visibility::Hidden));
}
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6 changes: 3 additions & 3 deletions compiler/rustc_codegen_llvm/src/allocator.rs
Original file line number Diff line number Diff line change
Expand Up @@ -76,7 +76,7 @@ pub(crate) unsafe fn codegen(
// __rust_alloc_error_handler_should_panic
let name = OomStrategy::SYMBOL;
let ll_g = llvm::LLVMRustGetOrInsertGlobal(llmod, name.as_ptr().cast(), name.len(), i8);
if tcx.sess.target.default_hidden_visibility {
if tcx.sess.default_hidden_visibility() {
llvm::LLVMRustSetVisibility(ll_g, llvm::Visibility::Hidden);
}
let val = tcx.sess.opts.unstable_opts.oom.should_panic();
Expand All @@ -85,7 +85,7 @@ pub(crate) unsafe fn codegen(

let name = NO_ALLOC_SHIM_IS_UNSTABLE;
let ll_g = llvm::LLVMRustGetOrInsertGlobal(llmod, name.as_ptr().cast(), name.len(), i8);
if tcx.sess.target.default_hidden_visibility {
if tcx.sess.default_hidden_visibility() {
llvm::LLVMRustSetVisibility(ll_g, llvm::Visibility::Hidden);
}
let llval = llvm::LLVMConstInt(i8, 0, False);
Expand Down Expand Up @@ -130,7 +130,7 @@ fn create_wrapper_function(
None
};

if tcx.sess.target.default_hidden_visibility {
if tcx.sess.default_hidden_visibility() {
llvm::LLVMRustSetVisibility(llfn, llvm::Visibility::Hidden);
}
if tcx.sess.must_emit_unwind_tables() {
Expand Down
4 changes: 2 additions & 2 deletions compiler/rustc_codegen_llvm/src/declare.rs
Original file line number Diff line number Diff line change
Expand Up @@ -84,7 +84,7 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
fn_type: &'ll Type,
) -> &'ll Value {
// Declare C ABI functions with the visibility used by C by default.
let visibility = if self.tcx.sess.target.default_hidden_visibility {
let visibility = if self.tcx.sess.default_hidden_visibility() {
llvm::Visibility::Hidden
} else {
llvm::Visibility::Default
Expand All @@ -107,7 +107,7 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
unnamed: llvm::UnnamedAddr,
fn_type: &'ll Type,
) -> &'ll Value {
let visibility = if self.tcx.sess.target.default_hidden_visibility {
let visibility = if self.tcx.sess.default_hidden_visibility() {
llvm::Visibility::Hidden
} else {
llvm::Visibility::Default
Expand Down
1 change: 1 addition & 0 deletions compiler/rustc_interface/src/tests.rs
Original file line number Diff line number Diff line change
Expand Up @@ -748,6 +748,7 @@ fn test_unstable_options_tracking_hash() {
tracked!(cross_crate_inline_threshold, InliningThreshold::Always);
tracked!(debug_info_for_profiling, true);
tracked!(debug_macros, true);
tracked!(default_hidden_visibility, Some(true));
tracked!(dep_info_omit_d_target, true);
tracked!(dual_proc_macros, true);
tracked!(dwarf_version, Some(5));
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2 changes: 1 addition & 1 deletion compiler/rustc_monomorphize/src/partitioning.rs
Original file line number Diff line number Diff line change
Expand Up @@ -883,7 +883,7 @@ fn mono_item_visibility<'tcx>(
}

fn default_visibility(tcx: TyCtxt<'_>, id: DefId, is_generic: bool) -> Visibility {
if !tcx.sess.target.default_hidden_visibility {
if !tcx.sess.default_hidden_visibility() {
return Visibility::Default;
}

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2 changes: 2 additions & 0 deletions compiler/rustc_session/src/options.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1552,6 +1552,8 @@ options! {
"compress debug info sections (none, zlib, zstd, default: none)"),
deduplicate_diagnostics: bool = (true, parse_bool, [UNTRACKED],
"deduplicate identical diagnostics (default: yes)"),
default_hidden_visibility: Option<bool> = (None, parse_opt_bool, [TRACKED],
"overrides the `default_hidden_visibility` setting of the target"),
dep_info_omit_d_target: bool = (false, parse_bool, [TRACKED],
"in dep-info output, omit targets for tracking dependencies of the dep-info files \
themselves (default: no)"),
Expand Down
8 changes: 8 additions & 0 deletions compiler/rustc_session/src/session.rs
Original file line number Diff line number Diff line change
Expand Up @@ -961,6 +961,14 @@ impl Session {
termize::dimensions().map_or(default_column_width, |(w, _)| w)
}
}

/// Whether the default visibility of symbols should be "hidden" rather than "default".
pub fn default_hidden_visibility(&self) -> bool {
self.opts
.unstable_opts
.default_hidden_visibility
.unwrap_or(self.target.options.default_hidden_visibility)
}
}

// JUSTIFICATION: defn of the suggested wrapper fns
Expand Down
6 changes: 5 additions & 1 deletion compiler/rustc_target/src/spec/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2094,7 +2094,11 @@ pub struct TargetOptions {
pub no_builtins: bool,

/// The default visibility for symbols in this target should be "hidden"
/// rather than "default"
/// rather than "default".
///
/// This value typically shouldn't be accessed directly, but through
/// the `rustc_session::Session::default_hidden_visibility` method, which
/// allows `rustc` users to override this setting using cmdline flags.
pub default_hidden_visibility: bool,

/// Whether a .debug_gdb_scripts section will be added to the output object file
Expand Down
Original file line number Diff line number Diff line change
@@ -0,0 +1,12 @@
# `default-hidden-visibility`

The tracking issue for this feature is: https://github.com/rust-lang/compiler-team/issues/656

------------------------

This flag can be used to override the target's
[`default_hidden_visibility`](https://doc.rust-lang.org/beta/nightly-rustc/rustc_target/spec/struct.TargetOptions.html#structfield.default_hidden_visibility)
setting.
Using `-Zdefault_hidden_visibility=yes` is roughly equivalent to Clang's
[`-fvisibility=hidden`](https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fvisibility)
cmdline flag.
31 changes: 31 additions & 0 deletions tests/codegen/default-hidden-visibility.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,31 @@
// Verifies that `Session::default_hidden_visibility` is affected when using the related cmdline
// flag. This is a regression test for https://github.com/rust-lang/compiler-team/issues/656. See
// also https://github.com/rust-lang/rust/issues/73295 and
// https://github.com/rust-lang/rust/issues/37530.

// revisions:DEFAULT YES NO
//[YES] compile-flags: -Zdefault-hidden-visibility=yes
//[NO] compile-flags: -Zdefault-hidden-visibility=no

// The test scenario is specifically about visibility of symbols exported out of dynamically linked
// libraries.
#![crate_type = "dylib"]

// The test scenario needs to use a Rust-public, but non-explicitly-exported symbol
// (e.g. the test doesn't use `#[no_mangle]`, because currently it implies that
// the symbol should be exported; we don't want that - we want to test the *default*
// export setting instead).
#[used]
pub static tested_symbol: [u8; 6] = *b"foobar";

// Exact LLVM IR differs depending on the target triple (e.g. `hidden constant`
// vs `internal constant` vs `constant`). Because of this, we only apply the
// specific test expectations below to one specific target triple. If needed,
// additional targets can be covered by adding copies of this test file with
// a different `only-X` directive.
//
// only-x86_64-unknown-linux-gnu

// DEFAULT: @{{.*}}default_hidden_visibility{{.*}}tested_symbol{{.*}} = constant
// YES: @{{.*}}default_hidden_visibility{{.*}}tested_symbol{{.*}} = hidden constant
// NO: @{{.*}}default_hidden_visibility{{.*}}tested_symbol{{.*}} = constant

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