Add function for setting up file and windbg logs

And also writing panics to those logs.

Cargo.lock

@@ -1813,6 +1813,15 @@ dependencies = [
  "value-bag",
 ]
 
+[[package]]
+name = "log-panics"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ae0136257df209261daa18d6c16394757c63e032e27aafd8b07788b051082bef"
+dependencies = [
+ "log",
+]
+
 [[package]]
 name = "lru"
 version = "0.7.5"
@@ -2005,14 +2014,18 @@ dependencies = [
  "crossbeam",
  "lazy_static",
  "libc",
+ "log",
+ "log-panics",
  "midi-consts",
  "nih_plug_derive",
  "parking_lot 0.12.0",
  "raw-window-handle",
  "serde",
  "serde_json",
+ "simplelog",
  "vst3-sys",
  "widestring",
+ "win_dbg_logger",
  "windows",
 ]
 
@@ -2176,6 +2189,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "num_threads"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "aba1801fb138d8e85e11d0fc70baf4fe1cdfffda7c6cd34a854905df588e5ed0"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "objc"
 version = "0.2.7"
@@ -3019,6 +3041,17 @@ dependencies = [
  "log",
 ]
 
+[[package]]
+name = "simplelog"
+version = "0.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "48dfff04aade74dd495b007c831cd6f4e0cee19c344dd9dc0884c0289b70a786"
+dependencies = [
+ "log",
+ "termcolor",
+ "time",
+]
+
 [[package]]
 name = "sine"
 version = "0.1.0"
@@ -3223,6 +3256,24 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "time"
+version = "0.3.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c2702e08a7a860f005826c6815dcac101b19b5eb330c27fe4a5928fec1d20ddd"
+dependencies = [
+ "itoa 1.0.1",
+ "libc",
+ "num_threads",
+ "time-macros",
+]
+
+[[package]]
+name = "time-macros"
+version = "0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "42657b1a6f4d817cda8e7a0ace261fe0cc946cf3a80314390b22cc61ae080792"
+
 [[package]]
 name = "tiny-skia"
 version = "0.6.3"
@@ -3853,6 +3904,15 @@ version = "1.0.0-beta.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e6f1efe828a707edf85994a4501734ac1c1b9d244cfcf4de235f11c4125ace8f"
 
+[[package]]
+name = "win_dbg_logger"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7d1b4c22244dc27534d81e2f6fc3efd6b20e50c010f177efc20b719ec759a779"
+dependencies = [
+ "log",
+]
+
 [[package]]
 name = "winapi"
 version = "0.3.9"

Cargo.toml

@@ -60,11 +60,14 @@ cfg-if = "1.0"
 clap-sys = { git = "https://github.com/robbert-vdh/clap-sys", branch = "update/clap-0.24" }
 crossbeam = "0.8"
 lazy_static = "1.4"
+log = { version = "0.4", features = ["std", "release_max_level_info"] }
+log-panics = "2.0"
 midi-consts = "0.1"
 parking_lot = "0.12"
 raw-window-handle = "0.4"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
+simplelog = "0.12"
 vst3-sys = { git = "https://github.com/robbert-vdh/vst3-sys.git", branch = "fix/note-off-event", optional = true }
 widestring = "1.0.0-beta.1"
 
@@ -73,6 +76,11 @@ assert_no_alloc = { version = "1.1", optional = true }
 [target.'cfg(all(target_family = "unix", not(target_os = "macos")))'.dependencies]
 libc = "0.2.124"
 
+[target.'cfg(target_os = "windows")'.dependencies]
+# STDIO isn't reliable on Windows, so when hosting plugins in a DAW it may be
+# useful to log using `OutputDebugString()` instead
+win_dbg_logger = "0.1"
+
 [target.'cfg(target_os = "windows")'.dependencies.windows]
 version = "0.32"
 features = [

src/wrapper/util.rs

@@ -1,6 +1,11 @@
 use std::cmp;
+use std::fs::File;
 use std::marker::PhantomData;
 use std::os::raw::c_char;
+use std::sync::atomic::{AtomicBool, Ordering};
+
+/// The environment variable for controlling the logging behavior.
+const NIH_LOG_ENV: &str = "NIH_LOG";
 
 #[cfg(all(debug_assertions, feature = "assert_process_allocs"))]
 #[global_allocator]
@@ -39,6 +44,83 @@ pub fn strlcpy(dest: &mut [c_char], src: &str) {
     dest[copy_len] = 0;
 }
 
+/// Set up the logger so that the `nih_*!()` logging and assertion macros log output to a
+/// centralized location and panics also get written there. By default this logs to STDERR unless
+/// the user is running Windows and a debugger has been attached, in which case
+/// `OutputDebugString()` will be used instead.
+///
+/// The logger's behavior can be controlled by setting the `NIH_LOG` environment variable to:
+///
+/// - `stderr`, in which case the log output always gets written to STDERR.
+/// - `windbg` (only on Windows), in which case the output always gets logged using
+///   `OutputDebugString()`.
+/// - A file path, in which case the output gets appended to the end of that file which will be
+///   created if necessary.
+///
+/// # TODO
+///
+/// Document `NIH_LOG` in an easier to find place.
+pub fn setup_logger() {
+    // `win_dbg_logger` has no way to let us know that the logger has already been set up, so we'll
+    // need to do it this way
+    static LOGGER_SET_UP: AtomicBool = AtomicBool::new(false);
+    if LOGGER_SET_UP
+        .compare_exchange(false, true, Ordering::SeqCst, Ordering::SeqCst)
+        .is_err()
+    {
+        return;
+    }
+
+    let nih_log_env = std::env::var(NIH_LOG_ENV);
+    let nih_log_env_str = nih_log_env.as_deref().unwrap_or("");
+
+    #[cfg(target_os = "windows")]
+    if nih_log_env_str.eq_ignore_ascii_case("windbg") || win_dbg_logger::is_debugger_present() {
+        win_dbg_logger::init();
+        log_panics::init();
+        return;
+    }
+
+    // If opening the file fails, then we'll log to STDERR anyways, hence this closure
+    let logger_config = simplelog::ConfigBuilder::new()
+        .set_thread_mode(simplelog::ThreadLogMode::Both)
+        .build();
+    let init_stderr_logger = || {
+        simplelog::TermLogger::init(
+            simplelog::LevelFilter::Trace,
+            logger_config.clone(),
+            simplelog::TerminalMode::Stderr,
+            simplelog::ColorChoice::Auto,
+        )
+    };
+
+    // If the logger has already been set up outside of this function then that won't cause any
+    // problems, so we can ignore the results here
+    if nih_log_env_str.eq_ignore_ascii_case("stderr") || nih_log_env_str.is_empty() {
+        let _ = init_stderr_logger();
+    } else {
+        let file = File::options()
+            .append(true)
+            .create(true)
+            .open(nih_log_env_str);
+        match file {
+            Ok(file) => {
+                let _ = simplelog::WriteLogger::init(
+                    simplelog::LevelFilter::Trace,
+                    logger_config,
+                    file,
+                );
+            }
+            Err(err) => {
+                let _ = init_stderr_logger();
+                nih_debug_assert_failure!("Could not open '{}': {:?}", nih_log_env_str, err);
+            }
+        }
+    }
+
+    log_panics::init();
+}
+
 /// A wrapper around the entire process function, including the plugin wrapper parts. This sets up
 /// `assert_no_alloc` if needed, while also making sure that things like FTZ are set up correctly if
 /// the host has not already done so.