Allow debugging output in the testing library.

concordium-std/src/lib.rs

@@ -392,3 +392,51 @@ static ALLOC: wee_alloc::WeeAlloc = wee_alloc::WeeAlloc::INIT;
     note = "Deprecated in favor of [concordium-smart-contract-testing](https://docs.rs/concordium-smart-contract-testing)."
 )]
 pub mod test_infrastructure;
+
+#[cfg(all(feature = "debug", not(feature = "std")))]
+pub use alloc::format;
+#[cfg(all(feature = "debug", feature = "std"))]
+pub use std::format;
+
+#[macro_export]
+#[cfg(feature = "debug")]
+macro_rules! concordium_dbg {
+    () => {
+        {
+            $crate::debug_print("", file!(), line!(), column!());
+        }
+    };
+    ($($arg:tt),+) => {
+        {
+            let msg = $crate::format!($($arg),+);
+            $crate::debug_print(&msg, file!(), line!(), column!());
+        }
+    };
+}
+
+#[macro_export]
+#[cfg(not(feature = "debug"))]
+macro_rules! concordium_dbg {
+    () => {{}};
+    ($($arg:tt),+) => {{}};
+}
+
+/// Emit a message in debug mode.
+/// Used internally, not meant to be called directly by contract writers,
+/// and a contract with this debug print cannot be deployed to the chain.
+#[doc(hidden)]
+#[cfg(feature = "debug")]
+pub fn debug_print(message: &str, filename: &str, line: u32, column: u32) {
+    let msg_bytes = message.as_bytes();
+    let filename_bytes = filename.as_bytes();
+    unsafe {
+        crate::prims::debug_print(
+            msg_bytes.as_ptr(),
+            msg_bytes.len() as u32,
+            filename_bytes.as_ptr(),
+            filename_bytes.len() as u32,
+            line,
+            column,
+        )
+    };
+}

concordium-std/src/prims.rs

@@ -282,6 +282,22 @@ extern "C" {
         column: u32,
     );
 
+    #[cfg(feature = "debug")]
+    /// Emit text together with the source location.
+    /// This is used as the equivalent of the `dbg!` macro when the
+    /// `enable-debug` feature is enabled.
+    ///
+    /// Note that this function is not allowed on the chain, it is only there to
+    /// ease local testing.
+    pub fn debug_print(
+        msg_start: *const u8,
+        msg_length: u32,
+        filename_start: *const u8,
+        filename_length: u32,
+        line: u32,
+        column: u32,
+    );
+
     #[cfg(all(feature = "wasm-test", feature = "concordium-quickcheck", target_arch = "wasm32"))]
     /// Generating random numbers for randomised testing.
     /// Not available for contracts deployed on the chain.