Enable assert_no_alloc in debug builds

Cargo.lock

@@ -8,6 +8,12 @@ version = "1.0.53"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "94a45b455c14666b85fc40a019e8ab9eb75e3a124e05494f5397122bc9eb06e0"
 
+[[package]]
+name = "assert_no_alloc"
+version = "1.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "55ca83137a482d61d916ceb1eba52a684f98004f18e0cafea230fe5579c178a3"
+
 [[package]]
 name = "autocfg"
 version = "1.0.1"
@@ -142,6 +148,8 @@ dependencies = [
 name = "nih_plug"
 version = "0.1.0"
 dependencies = [
+ "assert_no_alloc",
+ "cfg-if",
  "crossbeam",
  "lazy_static",
  "nih_plug_derive",

Cargo.toml

@@ -18,9 +18,18 @@ members = [
 nih_plug_derive = { path = "nih_plug_derive" }
 
 crossbeam = "0.8"
+cfg-if = "1.0"
 lazy_static = "1.4"
 parking_lot = "0.12"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 vst3-sys = { git = "https://github.com/robbert-vdh/vst3-sys.git", branch = "fix/atomic-reference-count" }
 widestring = "1.0.0-beta.1"
+
+assert_no_alloc = { version = "1.1", optional = true }
+
+[features]
+default = []
+# Enabling this feature will cause the plugin to terminate when allocations
+# occur in the processing function while compiling in debug mode.
+assert_process_allocs = ["assert_no_alloc"]

plugins/gain/Cargo.toml

@@ -8,6 +8,6 @@ license = "GPL-3.0-or-later"
 crate-type = ["cdylib"]
 
 [dependencies]
-nih_plug = { path = "../../" }
+nih_plug = { path = "../../", features = ["assert_process_allocs"] }
 
 parking_lot = "0.12"

plugins/sine/Cargo.toml

@@ -8,4 +8,4 @@ license = "GPL-3.0-or-later"
 crate-type = ["cdylib"]
 
 [dependencies]
-nih_plug = { path = "../../" }
+nih_plug = { path = "../../", features = ["assert_process_allocs"] }

src/wrapper/util.rs

@@ -19,6 +19,10 @@ use std::os::raw::c_char;
 use vst3_sys::vst::TChar;
 use widestring::U16CString;
 
+#[cfg(all(debug_assertions, feature = "assert_process_allocs"))]
+#[global_allocator]
+static A: assert_no_alloc::AllocDisabler = assert_no_alloc::AllocDisabler;
+
 /// A Rabin fingerprint based string hash for parameter ID strings.
 pub fn hash_param_id(id: &str) -> u32 {
     let mut overflow;
@@ -83,3 +87,16 @@ pub fn u16strlcpy(dest: &mut [TChar], src: &str) {
     dest[..copy_len].copy_from_slice(&src_utf16_chars_signed[..copy_len]);
     dest[copy_len] = 0;
 }
+
+/// 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.
+pub fn process_wrapper<T, F: FnOnce() -> T>(f: F) -> T {
+    cfg_if::cfg_if! {
+        if #[cfg(all(debug_assertions, feature = "assert_process_allocs"))] {
+            assert_no_alloc::assert_no_alloc(f)
+        } else {
+            f()
+        }
+    }
+}

src/wrapper/vst3.rs

@@ -47,7 +47,7 @@ use crate::param::range::Range;
 use crate::param::Param;
 use crate::plugin::{BufferConfig, BusConfig, Plugin, ProcessStatus, Vst3Plugin};
 use crate::wrapper::state::{ParamValue, State};
-use crate::wrapper::util::{hash_param_id, strlcpy, u16strlcpy};
+use crate::wrapper::util::{hash_param_id, process_wrapper, strlcpy, u16strlcpy};
 
 // Alias needed for the VST3 attribute macro
 use vst3_sys as vst3_com;
@@ -972,6 +972,9 @@ impl<P: Plugin> IAudioProcessor for Wrapper<'_, P> {
     unsafe fn process(&self, data: *mut vst3_sys::vst::ProcessData) -> tresult {
         check_null_ptr!(data);
 
+        // Panic on allocations if the `assert_process_allocs` feature has been enabled, and make
+        // sure that FTZ is set up correctly
+        process_wrapper(|| {
             // We need to handle incoming automation first
             let data = &*data;
             let sample_rate = self
@@ -1036,15 +1039,18 @@ impl<P: Plugin> IAudioProcessor for Wrapper<'_, P> {
                 (*data.outputs).buffers,
             );
 
-        // This vector has been reallocated to contain enough slices as there are output channels
+            // This vector has been reallocated to contain enough slices as there are output
+            // channels
             let mut output_buffer = self.inner.output_buffer.write();
             {
                 let output_slices = output_buffer.as_raw_vec();
                 nih_debug_assert_eq!(num_output_channels, output_slices.len());
-            for (output_channel_idx, output_channel_slice) in output_slices.iter_mut().enumerate() {
+                for (output_channel_idx, output_channel_slice) in
+                    output_slices.iter_mut().enumerate()
+                {
                     // SAFETY: These pointers may not be valid outside of this function even though
-                // their lifetime is equal to this structs. This is still safe because they are only
+                    // their lifetime is equal to this structs. This is still safe because they are
-                // dereferenced here later as part of this process function.
+                    // only dereferenced here later as part of this process function.
                     *output_channel_slice = std::slice::from_raw_parts_mut(
                         *((*data.outputs).buffers as *mut *mut f32).add(output_channel_idx),
                         data.num_samples as usize,
@@ -1053,8 +1059,8 @@ impl<P: Plugin> IAudioProcessor for Wrapper<'_, P> {
             }
 
             // Most hosts process data in place, in which case we don't need to do any copying
-        // ourselves. If the pointers do not alias, then we'll do the copy here and then the plugin
+            // ourselves. If the pointers do not alias, then we'll do the copy here and then the
-        // can just do normal in place processing.
+            // plugin can just do normal in place processing.
             if !data.inputs.is_null() {
                 let num_input_channels = (*data.inputs).num_channels as usize;
                 nih_debug_assert!(
@@ -1090,6 +1096,7 @@ impl<P: Plugin> IAudioProcessor for Wrapper<'_, P> {
                 }
                 _ => kResultOk,
             }
+        })
     }
 
     unsafe fn get_tail_samples(&self) -> u32 {