From 46becfdf9c807e0108a78bb4df9b8330b10422c8 Mon Sep 17 00:00:00 2001 From: Vadim Petrochenkov Date: Mon, 10 Apr 2023 14:20:38 +0300 Subject: [PATCH] expand: Change how `#![cfg(FALSE)]` behaves on crate root Previously it removed all other attributes from the crate root. Now it removes only attributes below itself. So it becomes possible to configure some global crate properties even for fully unconfigured crates. --- compiler/rustc_expand/src/config.rs | 8 +++++--- compiler/rustc_expand/src/expand.rs | 20 +++++++++++++++---- tests/ui/cfg/auxiliary/cfg_false_lib.rs | 6 ++---- .../auxiliary/cfg_false_lib_no_std_after.rs | 5 +++++ .../auxiliary/cfg_false_lib_no_std_before.rs | 8 ++++++++ tests/ui/cfg/cfg-false-feature.rs | 6 ++---- tests/ui/cfg/cfg-false-feature.stderr | 17 +++------------- tests/ui/cfg/cfg_false_no_std-1.rs | 10 ++++++++++ tests/ui/cfg/cfg_false_no_std-2.rs | 11 ++++++++++ tests/ui/cfg/cfg_false_no_std.rs | 3 +-- 10 files changed, 63 insertions(+), 31 deletions(-) create mode 100644 tests/ui/cfg/auxiliary/cfg_false_lib_no_std_after.rs create mode 100644 tests/ui/cfg/auxiliary/cfg_false_lib_no_std_before.rs create mode 100644 tests/ui/cfg/cfg_false_no_std-1.rs create mode 100644 tests/ui/cfg/cfg_false_no_std-2.rs diff --git a/compiler/rustc_expand/src/config.rs b/compiler/rustc_expand/src/config.rs index 690f80f6876..bcfa5313bde 100644 --- a/compiler/rustc_expand/src/config.rs +++ b/compiler/rustc_expand/src/config.rs @@ -197,9 +197,11 @@ pub fn pre_configure_attrs(sess: &Session, attrs: &[Attribute]) -> ast::AttrVec config_tokens: false, lint_node_id: ast::CRATE_NODE_ID, }; - let attrs: ast::AttrVec = - attrs.iter().flat_map(|attr| strip_unconfigured.process_cfg_attr(attr)).collect(); - if strip_unconfigured.in_cfg(&attrs) { attrs } else { ast::AttrVec::new() } + attrs + .iter() + .flat_map(|attr| strip_unconfigured.process_cfg_attr(attr)) + .take_while(|attr| !is_cfg(attr) || strip_unconfigured.cfg_true(attr).0) + .collect() } #[macro_export] diff --git a/compiler/rustc_expand/src/expand.rs b/compiler/rustc_expand/src/expand.rs index dd8863df195..9850723a857 100644 --- a/compiler/rustc_expand/src/expand.rs +++ b/compiler/rustc_expand/src/expand.rs @@ -1039,7 +1039,12 @@ fn wrap_flat_map_node_noop_flat_map( ) -> Result { Ok(noop_flat_map(node, collector)) } - fn expand_cfg_false(&mut self, collector: &mut InvocationCollector<'_, '_>, span: Span) { + fn expand_cfg_false( + &mut self, + collector: &mut InvocationCollector<'_, '_>, + _pos: usize, + span: Span, + ) { collector.cx.emit_err(RemoveNodeNotSupported { span, descr: Self::descr() }); } @@ -1409,8 +1414,15 @@ fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy { fn noop_visit(&mut self, visitor: &mut V) { noop_visit_crate(self, visitor) } - fn expand_cfg_false(&mut self, collector: &mut InvocationCollector<'_, '_>, _span: Span) { - self.attrs.clear(); + fn expand_cfg_false( + &mut self, + collector: &mut InvocationCollector<'_, '_>, + pos: usize, + _span: Span, + ) { + // Attributes above `cfg(FALSE)` are left in place, because we may want to configure + // some global crate properties even on fully unconfigured crates. + self.attrs.truncate(pos); // Standard prelude imports are left in the crate for backward compatibility. self.items.truncate(collector.cx.num_standard_library_imports); } @@ -1804,7 +1816,7 @@ fn visit_node + DummyAstNode>( continue; } - node.expand_cfg_false(self, span); + node.expand_cfg_false(self, pos, span); continue; } sym::cfg_attr => { diff --git a/tests/ui/cfg/auxiliary/cfg_false_lib.rs b/tests/ui/cfg/auxiliary/cfg_false_lib.rs index 3c011d72b02..6c2dbb44d2a 100644 --- a/tests/ui/cfg/auxiliary/cfg_false_lib.rs +++ b/tests/ui/cfg/auxiliary/cfg_false_lib.rs @@ -1,6 +1,4 @@ -// It is unclear whether a fully unconfigured crate should link to standard library, -// or what its `no_std`/`no_core`/`compiler_builtins` status, more precisely. -// Currently the usual standard library prelude is added to such crates, -// and therefore they link to libstd. +// `#![no_std]` on a fully unconfigured crate is respected if it's placed before `cfg(FALSE)`. +// This crate has no such attribute, therefore this crate does link to libstd. #![cfg(FALSE)] diff --git a/tests/ui/cfg/auxiliary/cfg_false_lib_no_std_after.rs b/tests/ui/cfg/auxiliary/cfg_false_lib_no_std_after.rs new file mode 100644 index 00000000000..3cfa6c510d0 --- /dev/null +++ b/tests/ui/cfg/auxiliary/cfg_false_lib_no_std_after.rs @@ -0,0 +1,5 @@ +// `#![no_std]` on a fully unconfigured crate is respected if it's placed before `cfg(FALSE)`. +// Therefore this crate does link to libstd. + +#![cfg(FALSE)] +#![no_std] diff --git a/tests/ui/cfg/auxiliary/cfg_false_lib_no_std_before.rs b/tests/ui/cfg/auxiliary/cfg_false_lib_no_std_before.rs new file mode 100644 index 00000000000..8e89545b8f4 --- /dev/null +++ b/tests/ui/cfg/auxiliary/cfg_false_lib_no_std_before.rs @@ -0,0 +1,8 @@ +// `#![no_std]` on a fully unconfigured crate is respected if it's placed before `cfg(FALSE)`. +// Therefore this crate doesn't link to libstd. + +// no-prefer-dynamic + +#![no_std] +#![crate_type = "lib"] +#![cfg(FALSE)] diff --git a/tests/ui/cfg/cfg-false-feature.rs b/tests/ui/cfg/cfg-false-feature.rs index 21ea3ec79b4..84c231562f1 100644 --- a/tests/ui/cfg/cfg-false-feature.rs +++ b/tests/ui/cfg/cfg-false-feature.rs @@ -1,5 +1,4 @@ -// It is unclear which features should be in effect in a fully unconfigured crate (issue #104633). -// Currently none on the features are in effect, so we get the feature gates reported. +// Features above `cfg(FALSE)` are in effect in a fully unconfigured crate (issue #104633). // check-pass // compile-flags: --crate-type lib @@ -8,8 +7,7 @@ #![cfg(FALSE)] #![feature(box_syntax)] -macro mac() {} //~ WARN `macro` is experimental - //~| WARN unstable syntax can change at any point in the future +macro mac() {} // OK trait A = Clone; //~ WARN trait aliases are experimental //~| WARN unstable syntax can change at any point in the future diff --git a/tests/ui/cfg/cfg-false-feature.stderr b/tests/ui/cfg/cfg-false-feature.stderr index 14673fbdb14..34093036205 100644 --- a/tests/ui/cfg/cfg-false-feature.stderr +++ b/tests/ui/cfg/cfg-false-feature.stderr @@ -1,5 +1,5 @@ warning: trait aliases are experimental - --> $DIR/cfg-false-feature.rs:14:1 + --> $DIR/cfg-false-feature.rs:12:1 | LL | trait A = Clone; | ^^^^^^^^^^^^^^^^ @@ -9,19 +9,8 @@ LL | trait A = Clone; = warning: unstable syntax can change at any point in the future, causing a hard error! = note: for more information, see issue #65860 -warning: `macro` is experimental - --> $DIR/cfg-false-feature.rs:11:1 - | -LL | macro mac() {} - | ^^^^^^^^^^^^^^ - | - = note: see issue #39412 for more information - = help: add `#![feature(decl_macro)]` to the crate attributes to enable - = warning: unstable syntax can change at any point in the future, causing a hard error! - = note: for more information, see issue #65860 - warning: box pattern syntax is experimental - --> $DIR/cfg-false-feature.rs:18:9 + --> $DIR/cfg-false-feature.rs:16:9 | LL | let box _ = Box::new(0); | ^^^^^ @@ -31,5 +20,5 @@ LL | let box _ = Box::new(0); = warning: unstable syntax can change at any point in the future, causing a hard error! = note: for more information, see issue #65860 -warning: 3 warnings emitted +warning: 2 warnings emitted diff --git a/tests/ui/cfg/cfg_false_no_std-1.rs b/tests/ui/cfg/cfg_false_no_std-1.rs new file mode 100644 index 00000000000..bcb49e51353 --- /dev/null +++ b/tests/ui/cfg/cfg_false_no_std-1.rs @@ -0,0 +1,10 @@ +// No error, panic handler is supplied by libstd linked though the empty library. + +// check-pass +// aux-build: cfg_false_lib_no_std_after.rs + +#![no_std] + +extern crate cfg_false_lib_no_std_after as _; + +fn main() {} diff --git a/tests/ui/cfg/cfg_false_no_std-2.rs b/tests/ui/cfg/cfg_false_no_std-2.rs new file mode 100644 index 00000000000..0a2bfd5f68b --- /dev/null +++ b/tests/ui/cfg/cfg_false_no_std-2.rs @@ -0,0 +1,11 @@ +// Error, the linked empty library is `no_std` and doesn't provide a panic handler. + +// dont-check-compiler-stderr +// error-pattern: `#[panic_handler]` function required, but not found +// aux-build: cfg_false_lib_no_std_before.rs + +#![no_std] + +extern crate cfg_false_lib_no_std_before as _; + +fn main() {} diff --git a/tests/ui/cfg/cfg_false_no_std.rs b/tests/ui/cfg/cfg_false_no_std.rs index 319ea078187..4fa831715ed 100644 --- a/tests/ui/cfg/cfg_false_no_std.rs +++ b/tests/ui/cfg/cfg_false_no_std.rs @@ -1,5 +1,4 @@ -// Currently no error because the panic handler is supplied by libstd linked though the empty -// library, but the desirable behavior is unclear (see comments in cfg_false_lib.rs). +// No error, panic handler is supplied by libstd linked though the empty library. // check-pass // aux-build: cfg_false_lib.rs