From 3a73ca587bb8a8fb52d6045fbe31d50d5a56ff19 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lo=C3=AFc=20BRANSTETT?= <lolo.branstett@numericable.fr>
Date: Wed, 29 Sep 2021 02:39:30 +0200
Subject: [PATCH] Implement --check-cfg option (RFC 3013)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Co-authored-by: Urgau <lolo.branstett@numericable.fr>
Co-authored-by: Marcelina Kościelnicka <mwk@0x04.net>
---
compiler/rustc_attr/src/builtin.rs | 31 ++++++-
compiler/rustc_driver/src/lib.rs | 2 +
compiler/rustc_interface/src/interface.rs | 91 ++++++++++++++++++-
compiler/rustc_interface/src/util.rs | 8 ++
compiler/rustc_lint_defs/src/builtin.rs | 38 ++++++++
compiler/rustc_session/src/config.rs | 89 +++++++++++++++++-
compiler/rustc_session/src/parse.rs | 4 +
compiler/rustc_span/src/symbol.rs | 2 +
src/librustdoc/core.rs | 1 +
src/librustdoc/doctest.rs | 1 +
src/test/run-make-fulldeps/issue-19371/foo.rs | 1 +
src/test/ui/check-cfg/empty-names.rs | 10 ++
src/test/ui/check-cfg/empty-names.stderr | 10 ++
src/test/ui/check-cfg/empty-values.rs | 6 ++
src/test/ui/check-cfg/empty-values.stderr | 2 +
.../invalid-arguments.anything_else.stderr | 2 +
...nvalid-arguments.names_simple_ident.stderr | 2 +
src/test/ui/check-cfg/invalid-arguments.rs | 10 ++
...valid-arguments.values_simple_ident.stderr | 2 +
...id-arguments.values_string_literals.stderr | 2 +
src/test/ui/check-cfg/invalid-cfg-name.rs | 14 +++
src/test/ui/check-cfg/invalid-cfg-name.stderr | 10 ++
src/test/ui/check-cfg/invalid-cfg-value.rs | 17 ++++
.../ui/check-cfg/invalid-cfg-value.stderr | 10 ++
.../feature-gates/feature-gate-check-cfg.rs | 3 +
.../feature-gate-check-cfg.stderr | 2 +
src/tools/tidy/src/ui_tests.rs | 2 +-
27 files changed, 365 insertions(+), 7 deletions(-)
create mode 100644 src/test/ui/check-cfg/empty-names.rs
create mode 100644 src/test/ui/check-cfg/empty-names.stderr
create mode 100644 src/test/ui/check-cfg/empty-values.rs
create mode 100644 src/test/ui/check-cfg/empty-values.stderr
create mode 100644 src/test/ui/check-cfg/invalid-arguments.anything_else.stderr
create mode 100644 src/test/ui/check-cfg/invalid-arguments.names_simple_ident.stderr
create mode 100644 src/test/ui/check-cfg/invalid-arguments.rs
create mode 100644 src/test/ui/check-cfg/invalid-arguments.values_simple_ident.stderr
create mode 100644 src/test/ui/check-cfg/invalid-arguments.values_string_literals.stderr
create mode 100644 src/test/ui/check-cfg/invalid-cfg-name.rs
create mode 100644 src/test/ui/check-cfg/invalid-cfg-name.stderr
create mode 100644 src/test/ui/check-cfg/invalid-cfg-value.rs
create mode 100644 src/test/ui/check-cfg/invalid-cfg-value.stderr
create mode 100644 src/test/ui/feature-gates/feature-gate-check-cfg.rs
create mode 100644 src/test/ui/feature-gates/feature-gate-check-cfg.stderr
diff --git a/compiler/rustc_attr/src/builtin.rs b/compiler/rustc_attr/src/builtin.rs
index dca7f5dd487..49043e9f5f9 100644
--- a/compiler/rustc_attr/src/builtin.rs
+++ b/compiler/rustc_attr/src/builtin.rs
@@ -1,10 +1,13 @@
//! Parsing and validation of builtin attributes
-use rustc_ast::{self as ast, Attribute, Lit, LitKind, MetaItem, MetaItemKind, NestedMetaItem};
+use rustc_ast as ast;
+use rustc_ast::node_id::CRATE_NODE_ID;
+use rustc_ast::{Attribute, Lit, LitKind, MetaItem, MetaItemKind, NestedMetaItem};
use rustc_ast_pretty::pprust;
use rustc_errors::{struct_span_err, Applicability};
use rustc_feature::{find_gated_cfg, is_builtin_attr_name, Features, GatedCfg};
use rustc_macros::HashStable_Generic;
+use rustc_session::lint::builtin::UNEXPECTED_CFGS;
use rustc_session::parse::{feature_err, ParseSess};
use rustc_session::Session;
use rustc_span::hygiene::Transparency;
@@ -458,8 +461,30 @@ pub fn cfg_matches(cfg: &ast::MetaItem, sess: &ParseSess, features: Option<&Feat
true
}
MetaItemKind::NameValue(..) | MetaItemKind::Word => {
- let ident = cfg.ident().expect("multi-segment cfg predicate");
- sess.config.contains(&(ident.name, cfg.value_str()))
+ let name = cfg.ident().expect("multi-segment cfg predicate").name;
+ let value = cfg.value_str();
+ if sess.check_config.names_checked && !sess.check_config.names_valid.contains(&name)
+ {
+ sess.buffer_lint(
+ UNEXPECTED_CFGS,
+ cfg.span,
+ CRATE_NODE_ID,
+ "unexpected `cfg` condition name",
+ );
+ }
+ if let Some(val) = value {
+ if sess.check_config.values_checked.contains(&name)
+ && !sess.check_config.values_valid.contains(&(name, val))
+ {
+ sess.buffer_lint(
+ UNEXPECTED_CFGS,
+ cfg.span,
+ CRATE_NODE_ID,
+ "unexpected `cfg` condition value",
+ );
+ }
+ }
+ sess.config.contains(&(name, value))
}
}
})
diff --git a/compiler/rustc_driver/src/lib.rs b/compiler/rustc_driver/src/lib.rs
index ca4e7b5142e..dd235063b5c 100644
--- a/compiler/rustc_driver/src/lib.rs
+++ b/compiler/rustc_driver/src/lib.rs
@@ -216,10 +216,12 @@ fn run_compiler(
}
let cfg = interface::parse_cfgspecs(matches.opt_strs("cfg"));
+ let check_cfg = interface::parse_check_cfg(matches.opt_strs("check-cfg"));
let (odir, ofile) = make_output(&matches);
let mut config = interface::Config {
opts: sopts,
crate_cfg: cfg,
+ crate_check_cfg: check_cfg,
input: Input::File(PathBuf::new()),
input_path: None,
output_file: ofile,
diff --git a/compiler/rustc_interface/src/interface.rs b/compiler/rustc_interface/src/interface.rs
index 237aef1cf23..81d33411c4e 100644
--- a/compiler/rustc_interface/src/interface.rs
+++ b/compiler/rustc_interface/src/interface.rs
@@ -2,7 +2,7 @@ pub use crate::passes::BoxedResolver;
use crate::util;
use rustc_ast::token;
-use rustc_ast::{self as ast, MetaItemKind};
+use rustc_ast::{self as ast, LitKind, MetaItemKind};
use rustc_codegen_ssa::traits::CodegenBackend;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_data_structures::sync::Lrc;
@@ -13,12 +13,13 @@ use rustc_lint::LintStore;
use rustc_middle::ty;
use rustc_parse::maybe_new_parser_from_source_str;
use rustc_query_impl::QueryCtxt;
-use rustc_session::config::{self, ErrorOutputType, Input, OutputFilenames};
+use rustc_session::config::{self, CheckCfg, ErrorOutputType, Input, OutputFilenames};
use rustc_session::early_error;
use rustc_session::lint;
use rustc_session::parse::{CrateConfig, ParseSess};
use rustc_session::{DiagnosticOutput, Session};
use rustc_span::source_map::{FileLoader, FileName};
+use rustc_span::symbol::sym;
use std::path::PathBuf;
use std::result;
use std::sync::{Arc, Mutex};
@@ -140,6 +141,90 @@ pub fn parse_cfgspecs(cfgspecs: Vec<String>) -> FxHashSet<(String, Option<String
})
}
+/// Converts strings provided as `--check-cfg [specs]` into a `CheckCfg`.
+pub fn parse_check_cfg(specs: Vec<String>) -> CheckCfg {
+ rustc_span::create_default_session_if_not_set_then(move |_| {
+ let mut cfg = CheckCfg::default();
+
+ 'specs: for s in specs {
+ let sess = ParseSess::with_silent_emitter(Some(format!(
+ "this error occurred on the command line: `--check-cfg={}`",
+ s
+ )));
+ let filename = FileName::cfg_spec_source_code(&s);
+
+ macro_rules! error {
+ ($reason: expr) => {
+ early_error(
+ ErrorOutputType::default(),
+ &format!(
+ concat!("invalid `--check-cfg` argument: `{}` (", $reason, ")"),
+ s
+ ),
+ );
+ };
+ }
+
+ match maybe_new_parser_from_source_str(&sess, filename, s.to_string()) {
+ Ok(mut parser) => match &mut parser.parse_meta_item() {
+ Ok(meta_item) if parser.token == token::Eof => {
+ if let Some(args) = meta_item.meta_item_list() {
+ if meta_item.has_name(sym::names) {
+ cfg.names_checked = true;
+ for arg in args {
+ if arg.is_word() && arg.ident().is_some() {
+ let ident = arg.ident().expect("multi-segment cfg key");
+ cfg.names_valid.insert(ident.name.to_string());
+ } else {
+ error!("`names()` arguments must be simple identifers");
+ }
+ }
+ continue 'specs;
+ } else if meta_item.has_name(sym::values) {
+ if let Some((name, values)) = args.split_first() {
+ if name.is_word() && name.ident().is_some() {
+ let ident = name.ident().expect("multi-segment cfg key");
+ cfg.values_checked.insert(ident.to_string());
+ for val in values {
+ if let Some(LitKind::Str(s, _)) =
+ val.literal().map(|lit| &lit.kind)
+ {
+ cfg.values_valid
+ .insert((ident.to_string(), s.to_string()));
+ } else {
+ error!(
+ "`values()` arguments must be string literals"
+ );
+ }
+ }
+
+ continue 'specs;
+ } else {
+ error!(
+ "`values()` first argument must be a simple identifer"
+ );
+ }
+ }
+ }
+ }
+ }
+ Ok(..) => {}
+ Err(err) => err.cancel(),
+ },
+ Err(errs) => errs.into_iter().for_each(|mut err| err.cancel()),
+ }
+
+ error!(
+ "expected `names(name1, name2, ... nameN)` or \
+ `values(name, \"value1\", \"value2\", ... \"valueN\")`"
+ );
+ }
+
+ cfg.names_valid.extend(cfg.values_checked.iter().cloned());
+ cfg
+ })
+}
+
/// The compiler configuration
pub struct Config {
/// Command line options
@@ -147,6 +232,7 @@ pub struct Config {
/// cfg! configuration in addition to the default ones
pub crate_cfg: FxHashSet<(String, Option<String>)>,
+ pub crate_check_cfg: CheckCfg,
pub input: Input,
pub input_path: Option<PathBuf>,
@@ -190,6 +276,7 @@ pub fn create_compiler_and_run<R>(config: Config, f: impl FnOnce(&Compiler) -> R
let (mut sess, codegen_backend) = util::create_session(
config.opts,
config.crate_cfg,
+ config.crate_check_cfg,
config.diagnostic_output,
config.file_loader,
config.input_path.clone(),
diff --git a/compiler/rustc_interface/src/util.rs b/compiler/rustc_interface/src/util.rs
index 6d9183eda9d..4b1b01de549 100644
--- a/compiler/rustc_interface/src/util.rs
+++ b/compiler/rustc_interface/src/util.rs
@@ -15,6 +15,7 @@ use rustc_parse::validate_attr;
use rustc_query_impl::QueryCtxt;
use rustc_resolve::{self, Resolver};
use rustc_session as session;
+use rustc_session::config::CheckCfg;
use rustc_session::config::{self, CrateType};
use rustc_session::config::{ErrorOutputType, Input, OutputFilenames};
use rustc_session::lint::{self, BuiltinLintDiagnostics, LintBuffer};
@@ -67,6 +68,7 @@ pub fn add_configuration(
pub fn create_session(
sopts: config::Options,
cfg: FxHashSet<(String, Option<String>)>,
+ check_cfg: CheckCfg,
diagnostic_output: DiagnosticOutput,
file_loader: Option<Box<dyn FileLoader + Send + Sync + 'static>>,
input_path: Option<PathBuf>,
@@ -102,7 +104,13 @@ pub fn create_session(
let mut cfg = config::build_configuration(&sess, config::to_crate_config(cfg));
add_configuration(&mut cfg, &mut sess, &*codegen_backend);
+
+ let mut check_cfg = config::to_crate_check_config(check_cfg);
+ check_cfg.fill_well_known();
+ check_cfg.fill_actual(&cfg);
+
sess.parse_sess.config = cfg;
+ sess.parse_sess.check_config = check_cfg;
(Lrc::new(sess), Lrc::new(codegen_backend))
}
diff --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs
index f4eba25475e..adec1a3ab00 100644
--- a/compiler/rustc_lint_defs/src/builtin.rs
+++ b/compiler/rustc_lint_defs/src/builtin.rs
@@ -2957,6 +2957,43 @@ declare_lint! {
};
}
+declare_lint! {
+ /// The `unexpected_cfgs` lint detects unexpected conditional compilation conditions.
+ ///
+ /// ### Example
+ ///
+ /// ```text
+ /// rustc --check-cfg 'names()'
+ /// ```
+ ///
+ /// ```rust,ignore (needs command line option)
+ /// #[cfg(widnows)]
+ /// fn foo() {}
+ /// ```
+ ///
+ /// This will produce:
+ ///
+ /// ```text
+ /// warning: unknown condition name used
+ /// --> lint_example.rs:1:7
+ /// |
+ /// 1 | #[cfg(widnows)]
+ /// | ^^^^^^^
+ /// |
+ /// = note: `#[warn(unexpected_cfgs)]` on by default
+ /// ```
+ ///
+ /// ### Explanation
+ ///
+ /// This lint is only active when a `--check-cfg='names(...)'` option has been passed
+ /// to the compiler and triggers whenever an unknown condition name or value is used.
+ /// The known condition include names or values passed in `--check-cfg`, `--cfg`, and some
+ /// well-knows names and values built into the compiler.
+ pub UNEXPECTED_CFGS,
+ Warn,
+ "detects unexpected names and values in `#[cfg]` conditions",
+}
+
declare_lint_pass! {
/// Does nothing as a lint pass, but registers some `Lint`s
/// that are used by other parts of the compiler.
@@ -3055,6 +3092,7 @@ declare_lint_pass! {
DEPRECATED_CFG_ATTR_CRATE_TYPE_NAME,
DUPLICATE_MACRO_ATTRIBUTES,
SUSPICIOUS_AUTO_TRAIT_IMPLS,
+ UNEXPECTED_CFGS,
]
}
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index 8630ffec241..f90766875d2 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -16,7 +16,7 @@ use rustc_target::spec::{LinkerFlavor, SplitDebuginfo, Target, TargetTriple, Tar
use rustc_serialize::json;
-use crate::parse::CrateConfig;
+use crate::parse::{CrateCheckConfig, CrateConfig};
use rustc_feature::UnstableFeatures;
use rustc_span::edition::{Edition, DEFAULT_EDITION, EDITION_NAME_LIST, LATEST_STABLE_EDITION};
use rustc_span::source_map::{FileName, FilePathMapping};
@@ -921,6 +921,7 @@ pub const fn default_lib_output() -> CrateType {
}
fn default_configuration(sess: &Session) -> CrateConfig {
+ // NOTE: This should be kept in sync with `CrateCheckConfig::fill_well_known` below.
let end = &sess.target.endian;
let arch = &sess.target.arch;
let wordsz = sess.target.pointer_width.to_string();
@@ -1005,6 +1006,91 @@ pub fn to_crate_config(cfg: FxHashSet<(String, Option<String>)>) -> CrateConfig
cfg.into_iter().map(|(a, b)| (Symbol::intern(&a), b.map(|b| Symbol::intern(&b)))).collect()
}
+/// The parsed `--check-cfg` options
+pub struct CheckCfg<T = String> {
+ /// Set if `names()` checking is enabled
+ pub names_checked: bool,
+ /// The union of all `names()`
+ pub names_valid: FxHashSet<T>,
+ /// The set of names for which `values()` was used
+ pub values_checked: FxHashSet<T>,
+ /// The set of all (name, value) pairs passed in `values()`
+ pub values_valid: FxHashSet<(T, T)>,
+}
+
+impl<T> Default for CheckCfg<T> {
+ fn default() -> Self {
+ CheckCfg {
+ names_checked: false,
+ names_valid: FxHashSet::default(),
+ values_checked: FxHashSet::default(),
+ values_valid: FxHashSet::default(),
+ }
+ }
+}
+
+impl<T> CheckCfg<T> {
+ fn map_data<O: Eq + Hash>(&self, f: impl Fn(&T) -> O) -> CheckCfg<O> {
+ CheckCfg {
+ names_checked: self.names_checked,
+ names_valid: self.names_valid.iter().map(|a| f(a)).collect(),
+ values_checked: self.values_checked.iter().map(|a| f(a)).collect(),
+ values_valid: self.values_valid.iter().map(|(a, b)| (f(a), f(b))).collect(),
+ }
+ }
+}
+
+/// Converts the crate `--check-cfg` options from `String` to `Symbol`.
+/// `rustc_interface::interface::Config` accepts this in the compiler configuration,
+/// but the symbol interner is not yet set up then, so we must convert it later.
+pub fn to_crate_check_config(cfg: CheckCfg) -> CrateCheckConfig {
+ cfg.map_data(|s| Symbol::intern(s))
+}
+
+impl CrateCheckConfig {
+ /// Fills a `CrateCheckConfig` with well-known configuration names.
+ pub fn fill_well_known(&mut self) {
+ // NOTE: This should be kept in sync with `default_configuration`
+ const WELL_KNOWN_NAMES: &[Symbol] = &[
+ sym::unix,
+ sym::windows,
+ sym::target_os,
+ sym::target_family,
+ sym::target_arch,
+ sym::target_endian,
+ sym::target_pointer_width,
+ sym::target_env,
+ sym::target_abi,
+ sym::target_vendor,
+ sym::target_thread_local,
+ sym::target_has_atomic_load_store,
+ sym::target_has_atomic,
+ sym::target_has_atomic_equal_alignment,
+ sym::panic,
+ sym::sanitize,
+ sym::debug_assertions,
+ sym::proc_macro,
+ sym::test,
+ sym::doc,
+ sym::doctest,
+ sym::feature,
+ ];
+ for &name in WELL_KNOWN_NAMES {
+ self.names_valid.insert(name);
+ }
+ }
+
+ /// Fills a `CrateCheckConfig` with configuration names and values that are actually active.
+ pub fn fill_actual(&mut self, cfg: &CrateConfig) {
+ for &(k, v) in cfg {
+ self.names_valid.insert(k);
+ if let Some(v) = v {
+ self.values_valid.insert((k, v));
+ }
+ }
+ }
+}
+
pub fn build_configuration(sess: &Session, mut user_cfg: CrateConfig) -> CrateConfig {
// Combine the configuration requested by the session (command line) with
// some default and generated configuration items.
@@ -1148,6 +1234,7 @@ pub fn rustc_short_optgroups() -> Vec<RustcOptGroup> {
vec![
opt::flag_s("h", "help", "Display this message"),
opt::multi_s("", "cfg", "Configure the compilation environment", "SPEC"),
+ opt::multi("", "check-cfg", "Provide list of valid cfg options for checking", "SPEC"),
opt::multi_s(
"L",
"",
diff --git a/compiler/rustc_session/src/parse.rs b/compiler/rustc_session/src/parse.rs
index d5b520325e5..7113f9b0a2f 100644
--- a/compiler/rustc_session/src/parse.rs
+++ b/compiler/rustc_session/src/parse.rs
@@ -1,6 +1,7 @@
//! Contains `ParseSess` which holds state living beyond what one `Parser` might.
//! It also serves as an input to the parser itself.
+use crate::config::CheckCfg;
use crate::lint::{BufferedEarlyLint, BuiltinLintDiagnostics, Lint, LintId};
use rustc_ast::node_id::NodeId;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
@@ -18,6 +19,7 @@ use std::str;
/// The set of keys (and, optionally, values) that define the compilation
/// environment of the crate, used to drive conditional compilation.
pub type CrateConfig = FxHashSet<(Symbol, Option<Symbol>)>;
+pub type CrateCheckConfig = CheckCfg<Symbol>;
/// Collected spans during parsing for places where a certain feature was
/// used and should be feature gated accordingly in `check_crate`.
@@ -117,6 +119,7 @@ pub struct ParseSess {
pub span_diagnostic: Handler,
pub unstable_features: UnstableFeatures,
pub config: CrateConfig,
+ pub check_config: CrateCheckConfig,
pub edition: Edition,
pub missing_fragment_specifiers: Lock<FxHashMap<Span, NodeId>>,
/// Places where raw identifiers were used. This is used to avoid complaining about idents
@@ -162,6 +165,7 @@ impl ParseSess {
span_diagnostic: handler,
unstable_features: UnstableFeatures::from_environment(None),
config: FxHashSet::default(),
+ check_config: CrateCheckConfig::default(),
edition: ExpnId::root().expn_data().edition,
missing_fragment_specifiers: Default::default(),
raw_identifier_spans: Lock::new(Vec::new()),
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index cab1d4e21c9..1d8b5ab75c2 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -908,6 +908,7 @@ symbols! {
naked,
naked_functions,
name,
+ names,
native_link_modifiers,
native_link_modifiers_as_needed,
native_link_modifiers_bundle,
@@ -1478,6 +1479,7 @@ symbols! {
va_list,
va_start,
val,
+ values,
var,
variant_count,
vec,
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index 1f14a333c00..5d2f774f8cf 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -250,6 +250,7 @@ crate fn create_config(
interface::Config {
opts: sessopts,
crate_cfg: interface::parse_cfgspecs(cfgs),
+ crate_check_cfg: interface::parse_check_cfg(vec![]),
input,
input_path: cpath,
output_file: None,
diff --git a/src/librustdoc/doctest.rs b/src/librustdoc/doctest.rs
index 6c55721c0dd..6f398c17683 100644
--- a/src/librustdoc/doctest.rs
+++ b/src/librustdoc/doctest.rs
@@ -91,6 +91,7 @@ crate fn run(options: RustdocOptions) -> Result<(), ErrorReported> {
let config = interface::Config {
opts: sessopts,
crate_cfg: interface::parse_cfgspecs(cfgs),
+ crate_check_cfg: interface::parse_check_cfg(vec![]),
input,
input_path: None,
output_file: None,
diff --git a/src/test/run-make-fulldeps/issue-19371/foo.rs b/src/test/run-make-fulldeps/issue-19371/foo.rs
index 4acabbb70ed..ec711eb4e48 100644
--- a/src/test/run-make-fulldeps/issue-19371/foo.rs
+++ b/src/test/run-make-fulldeps/issue-19371/foo.rs
@@ -49,6 +49,7 @@ fn compile(code: String, output: PathBuf, sysroot: PathBuf) {
let config = interface::Config {
opts,
crate_cfg: Default::default(),
+ crate_check_cfg: Default::default(),
input,
input_path: None,
output_file: Some(output),
diff --git a/src/test/ui/check-cfg/empty-names.rs b/src/test/ui/check-cfg/empty-names.rs
new file mode 100644
index 00000000000..046ff0364e2
--- /dev/null
+++ b/src/test/ui/check-cfg/empty-names.rs
@@ -0,0 +1,10 @@
+// Check warning for unexpected cfg
+//
+// check-pass
+// compile-flags: --check-cfg=names() -Z unstable-options
+
+#[cfg(unknown_key = "value")]
+//~^ WARNING unexpected `cfg` condition name
+pub fn f() {}
+
+fn main() {}
diff --git a/src/test/ui/check-cfg/empty-names.stderr b/src/test/ui/check-cfg/empty-names.stderr
new file mode 100644
index 00000000000..f926d1133cc
--- /dev/null
+++ b/src/test/ui/check-cfg/empty-names.stderr
@@ -0,0 +1,10 @@
+warning: unexpected `cfg` condition name
+ --> $DIR/empty-names.rs:6:7
+ |
+LL | #[cfg(unknown_key = "value")]
+ | ^^^^^^^^^^^^^^^^^^^^^
+ |
+ = note: `#[warn(unexpected_cfgs)]` on by default
+
+warning: 1 warning emitted
+
diff --git a/src/test/ui/check-cfg/empty-values.rs b/src/test/ui/check-cfg/empty-values.rs
new file mode 100644
index 00000000000..38ef9e51c7a
--- /dev/null
+++ b/src/test/ui/check-cfg/empty-values.rs
@@ -0,0 +1,6 @@
+// Check that a an empty values() is rejected
+//
+// check-fail
+// compile-flags: --check-cfg=values() -Z unstable-options
+
+fn main() {}
diff --git a/src/test/ui/check-cfg/empty-values.stderr b/src/test/ui/check-cfg/empty-values.stderr
new file mode 100644
index 00000000000..106d5b7b47f
--- /dev/null
+++ b/src/test/ui/check-cfg/empty-values.stderr
@@ -0,0 +1,2 @@
+error: invalid `--check-cfg` argument: `values()` (expected `names(name1, name2, ... nameN)` or `values(name, "value1", "value2", ... "valueN")`)
+
diff --git a/src/test/ui/check-cfg/invalid-arguments.anything_else.stderr b/src/test/ui/check-cfg/invalid-arguments.anything_else.stderr
new file mode 100644
index 00000000000..850924d993a
--- /dev/null
+++ b/src/test/ui/check-cfg/invalid-arguments.anything_else.stderr
@@ -0,0 +1,2 @@
+error: invalid `--check-cfg` argument: `anything_else(...)` (expected `names(name1, name2, ... nameN)` or `values(name, "value1", "value2", ... "valueN")`)
+
diff --git a/src/test/ui/check-cfg/invalid-arguments.names_simple_ident.stderr b/src/test/ui/check-cfg/invalid-arguments.names_simple_ident.stderr
new file mode 100644
index 00000000000..bdfbc3d54a2
--- /dev/null
+++ b/src/test/ui/check-cfg/invalid-arguments.names_simple_ident.stderr
@@ -0,0 +1,2 @@
+error: invalid `--check-cfg` argument: `names("NOT_IDENT")` (`names()` arguments must be simple identifers)
+
diff --git a/src/test/ui/check-cfg/invalid-arguments.rs b/src/test/ui/check-cfg/invalid-arguments.rs
new file mode 100644
index 00000000000..5090ce3e845
--- /dev/null
+++ b/src/test/ui/check-cfg/invalid-arguments.rs
@@ -0,0 +1,10 @@
+// Check that invalid --check-cfg are rejected
+//
+// check-fail
+// revisions: anything_else names_simple_ident values_simple_ident values_string_literals
+// [anything_else]compile-flags: -Z unstable-options --check-cfg=anything_else(...)
+// [names_simple_ident]compile-flags: -Z unstable-options --check-cfg=names("NOT_IDENT")
+// [values_simple_ident]compile-flags: -Z unstable-options --check-cfg=values("NOT_IDENT")
+// [values_string_literals]compile-flags: -Z unstable-options --check-cfg=values(test,12)
+
+fn main() {}
diff --git a/src/test/ui/check-cfg/invalid-arguments.values_simple_ident.stderr b/src/test/ui/check-cfg/invalid-arguments.values_simple_ident.stderr
new file mode 100644
index 00000000000..b25882baaf3
--- /dev/null
+++ b/src/test/ui/check-cfg/invalid-arguments.values_simple_ident.stderr
@@ -0,0 +1,2 @@
+error: invalid `--check-cfg` argument: `values("NOT_IDENT")` (`values()` first argument must be a simple identifer)
+
diff --git a/src/test/ui/check-cfg/invalid-arguments.values_string_literals.stderr b/src/test/ui/check-cfg/invalid-arguments.values_string_literals.stderr
new file mode 100644
index 00000000000..5853b4741a6
--- /dev/null
+++ b/src/test/ui/check-cfg/invalid-arguments.values_string_literals.stderr
@@ -0,0 +1,2 @@
+error: invalid `--check-cfg` argument: `values(test,12)` (`values()` arguments must be string literals)
+
diff --git a/src/test/ui/check-cfg/invalid-cfg-name.rs b/src/test/ui/check-cfg/invalid-cfg-name.rs
new file mode 100644
index 00000000000..8499d3d4448
--- /dev/null
+++ b/src/test/ui/check-cfg/invalid-cfg-name.rs
@@ -0,0 +1,14 @@
+// Check warning for invalid configuration name
+//
+// edition:2018
+// check-pass
+// compile-flags: --check-cfg=names() -Z unstable-options
+
+#[cfg(widnows)]
+//~^ WARNING unexpected `cfg` condition name
+pub fn f() {}
+
+#[cfg(windows)]
+pub fn g() {}
+
+pub fn main() {}
diff --git a/src/test/ui/check-cfg/invalid-cfg-name.stderr b/src/test/ui/check-cfg/invalid-cfg-name.stderr
new file mode 100644
index 00000000000..2587685afa0
--- /dev/null
+++ b/src/test/ui/check-cfg/invalid-cfg-name.stderr
@@ -0,0 +1,10 @@
+warning: unexpected `cfg` condition name
+ --> $DIR/invalid-cfg-name.rs:7:7
+ |
+LL | #[cfg(widnows)]
+ | ^^^^^^^
+ |
+ = note: `#[warn(unexpected_cfgs)]` on by default
+
+warning: 1 warning emitted
+
diff --git a/src/test/ui/check-cfg/invalid-cfg-value.rs b/src/test/ui/check-cfg/invalid-cfg-value.rs
new file mode 100644
index 00000000000..a60095a5aae
--- /dev/null
+++ b/src/test/ui/check-cfg/invalid-cfg-value.rs
@@ -0,0 +1,17 @@
+// Check warning for invalid configuration value
+//
+// edition:2018
+// check-pass
+// compile-flags: --check-cfg=values(feature,"serde","full") --cfg=feature="rand" -Z unstable-options
+
+#[cfg(feature = "sedre")]
+//~^ WARNING unexpected `cfg` condition value
+pub fn f() {}
+
+#[cfg(feature = "serde")]
+pub fn g() {}
+
+#[cfg(feature = "rand")]
+pub fn h() {}
+
+pub fn main() {}
diff --git a/src/test/ui/check-cfg/invalid-cfg-value.stderr b/src/test/ui/check-cfg/invalid-cfg-value.stderr
new file mode 100644
index 00000000000..c591d8474a2
--- /dev/null
+++ b/src/test/ui/check-cfg/invalid-cfg-value.stderr
@@ -0,0 +1,10 @@
+warning: unexpected `cfg` condition value
+ --> $DIR/invalid-cfg-value.rs:7:7
+ |
+LL | #[cfg(feature = "sedre")]
+ | ^^^^^^^^^^^^^^^^^
+ |
+ = note: `#[warn(unexpected_cfgs)]` on by default
+
+warning: 1 warning emitted
+
diff --git a/src/test/ui/feature-gates/feature-gate-check-cfg.rs b/src/test/ui/feature-gates/feature-gate-check-cfg.rs
new file mode 100644
index 00000000000..4012a3b04b5
--- /dev/null
+++ b/src/test/ui/feature-gates/feature-gate-check-cfg.rs
@@ -0,0 +1,3 @@
+// compile-flags: --check-cfg "names()"
+
+fn main() {}
diff --git a/src/test/ui/feature-gates/feature-gate-check-cfg.stderr b/src/test/ui/feature-gates/feature-gate-check-cfg.stderr
new file mode 100644
index 00000000000..9b27c2bc058
--- /dev/null
+++ b/src/test/ui/feature-gates/feature-gate-check-cfg.stderr
@@ -0,0 +1,2 @@
+error: the `-Z unstable-options` flag must also be passed to enable the flag `check-cfg`
+
diff --git a/src/tools/tidy/src/ui_tests.rs b/src/tools/tidy/src/ui_tests.rs
index 203e33e8b1f..95847dcd46b 100644
--- a/src/tools/tidy/src/ui_tests.rs
+++ b/src/tools/tidy/src/ui_tests.rs
@@ -7,7 +7,7 @@ use std::path::Path;
const ENTRY_LIMIT: usize = 1000;
// FIXME: The following limits should be reduced eventually.
-const ROOT_ENTRY_LIMIT: usize = 982;
+const ROOT_ENTRY_LIMIT: usize = 983;
const ISSUES_ENTRY_LIMIT: usize = 2310;
fn check_entries(path: &Path, bad: &mut bool) {