Hard-code dependent crate feature flags

When we generate bindings, we generate bindings across the API
surface of whatever features we had set. Thus, any generated
bindings are specific to the features we had set and it doesn't
make sense to have features on the `lightning-c-bindings` crate as
setting the wrong one will simply lead to a compilation failure.

Instead, here we hard-code the features in the dependencies section
of `Cargo.toml`.

Sadly, because we want to take an optional `core2` dependency, we
can't quite fully drop the `lightning-c-bindings` features
entirely, but after upgrading to rust-bitcoin 0.32 we should be
able to.

Author: TheBlueMatt

c-bindings-gen/src/main.rs

@@ -2102,9 +2102,7 @@ fn convert_file<'a, 'b>(libast: &'a FullLibraryAST, crate_types: &CrateTypes<'a>
 			// TODO: We need to map deny(missing_docs) in the source crate(s)
 			//writeln!(out, "#![deny(missing_docs)]").unwrap();
 
-			writeln!(out, "#![cfg_attr(not(feature = \"std\"), no_std)]").unwrap();
-			writeln!(out, "#[cfg(not(any(feature = \"std\", feature = \"no-std\")))]").unwrap();
-			writeln!(out, "compile_error!(\"at least one of the `std` or `no-std` features must be enabled\");").unwrap();
+			writeln!(out, "#![cfg_attr(feature = \"no-std\", no_std)]").unwrap();
 			writeln!(out, "extern crate alloc;").unwrap();
 
 			writeln!(out, "pub mod version;").unwrap();

genbindings.sh

@@ -180,11 +180,13 @@ pub mod $2 {
 	echo "}" >> /tmp/$1-crate-source.txt
 	cat /tmp/$1-crate-source.txt >> /tmp/crate-source.txt
 	rm /tmp/$1-crate-source.txt
+	FEATURES="$(echo "$3\"" | sed 's/--features=/"/' | sed 's/,/", "/g')"
+	[ "$FEATURES" = '"' ] && FEATURES=""
 	if is_gnu_sed; then
-		sed -E -i 's|#*'$1' = \{ .*|'$1' = \{ path = "'"$LIGHTNING_PATH"'/'$1'", default-features = false }|' lightning-c-bindings/Cargo.toml
+		sed -E -i 's|#*'$1' = \{ .*|'$1' = \{ path = "'"$LIGHTNING_PATH"'/'$1'", default-features = false, features = ['"$FEATURES"'] }|' lightning-c-bindings/Cargo.toml
 	else
 		# OSX sed is for some reason not compatible with GNU sed
-		sed -E -i '' 's|#*'$1' = \{ .*|'$1' = \{ path = "'"$LIGHTNING_PATH"'/'$1'", default-features = false }|' lightning-c-bindings/Cargo.toml
+		sed -E -i '' 's|#*'$1' = \{ .*|'$1' = \{ path = "'"$LIGHTNING_PATH"'/'$1'", default-features = false, features = ['"$FEATURES"'] }|' lightning-c-bindings/Cargo.toml
 	fi
 }
 
@@ -204,7 +206,6 @@ if [ "$2" = "true" ]; then
 	add_crate "lightning-background-processor" "lightning_background_processor" --features=std
 	add_crate "lightning-invoice" "lightning_invoice" --features=std
 	add_crate "lightning-rapid-gossip-sync" "lightning_rapid_gossip_sync" --features=std
-	CARGO_BUILD_ARGS="--features=std"
 else
 	add_crate lightning lightning --features=no-std
 	drop_crate "lightning-persister"

lightning-c-bindings/Cargo.toml

@@ -15,18 +15,17 @@ crate-type = ["staticlib"
 ,"cdylib"]
 
 [features]
-no-std = ["bitcoin/no-std", "lightning/no-std", "lightning-invoice/no-std", "lightning-background-processor/no-std", "core2"]
-std = ["bitcoin/std", "lightning/std", "lightning-invoice/std", "lightning-background-processor/std"]
+no-std = ["core2"]
 
 [dependencies]
 bitcoin = { version = "0.30", default-features = false }
 secp256k1 = { version = "0.27", features = ["global-context", "recovery"] }
 # Note that the following line is matched by genbindings to update the path
-lightning = { git = "https://github.com/lightningdevkit/rust-lightning", branch = "0.0.123-bindings", default-features = false }
+lightning = { git = "https://github.com/lightningdevkit/rust-lightning", branch = "0.0.123-bindings", default-features = false, features = ["std"] }
 lightning-persister = { git = "https://github.com/lightningdevkit/rust-lightning", branch = "0.0.123-bindings", default-features = false }
-lightning-invoice = { git = "https://github.com/lightningdevkit/rust-lightning", branch = "0.0.123-bindings", default-features = false }
-lightning-background-processor = { git = "https://github.com/lightningdevkit/rust-lightning", branch = "0.0.123-bindings", default-features = false }
-lightning-rapid-gossip-sync = { git = "https://github.com/lightningdevkit/rust-lightning", branch = "0.0.123-bindings", default-features = false }
+lightning-invoice = { git = "https://github.com/lightningdevkit/rust-lightning", branch = "0.0.123-bindings", default-features = false, features = ["std"] }
+lightning-background-processor = { git = "https://github.com/lightningdevkit/rust-lightning", branch = "0.0.123-bindings", default-features = false, features = ["std"] }
+lightning-rapid-gossip-sync = { git = "https://github.com/lightningdevkit/rust-lightning", branch = "0.0.123-bindings", default-features = false, features = ["std"] }
 
 core2 = { version = "0.3.0", optional = true, default-features = false }
 

lightning-c-bindings/src/c_types/mod.rs

@@ -24,11 +24,10 @@ use core::convert::TryInto; // Bindings need at least rustc 1.34
 use alloc::borrow::ToOwned;
 use core::ffi::c_void;
 
-#[cfg(feature = "std")]
+#[cfg(not(feature = "no-std"))]
 pub(crate) use std::io::{self, Cursor, Read};
 #[cfg(feature = "no-std")]
 pub(crate) use core2::io::{self, Cursor, Read};
-#[cfg(feature = "no-std")]
 use alloc::{boxed::Box, vec::Vec, string::String};
 
 use core::convert::TryFrom;
@@ -869,7 +868,7 @@ impl Str {
 		};
 		String::from_utf8(bytes).unwrap()
 	}
-	#[cfg(feature = "std")]
+	#[cfg(not(feature = "no-std"))]
 	pub(crate) fn into_pathbuf(mut self) -> std::path::PathBuf {
 		std::path::PathBuf::from(self.into_string())
 	}
@@ -880,7 +879,7 @@ impl Into<Str> for String {
 		Str { chars: s.as_ptr(), len: s.len(), chars_is_owned: true }
 	}
 }
-#[cfg(feature = "std")]
+#[cfg(not(feature = "no-std"))]
 impl Into<Str> for std::path::PathBuf {
 	fn into(self) -> Str {
 		self.into_os_string().into_string().expect("We expect paths to be UTF-8 valid").into()

lightning-c-bindings/src/lib.rs

@@ -16,9 +16,7 @@
 #![allow(unused_parens)]
 #![allow(unused_unsafe)]
 #![allow(unused_braces)]
-#![cfg_attr(not(feature = "std"), no_std)]
-#[cfg(not(any(feature = "std", feature = "no-std")))]
-compile_error!("at least one of the `std` or `no-std` features must be enabled");
+#![cfg_attr(feature = "no-std", no_std)]
 extern crate alloc;
 pub mod version;
 pub mod c_types;