handle panics

.github/workflows/rust.yml

@@ -37,15 +37,23 @@ jobs:
         run: curl -LsSf https://get.nexte.st/latest/linux | tar zxf - -C /usr/local/bin
 
       - name: Build
-        run: cargo build --all-features
+        run: |
+          cargo build --no-default-features --features static
+          cargo build --no-default-features --features static,std
+          cargo build --no-default-features --features dynamic
+          cargo build --no-default-features --features dynamic,std
 
       - name: Test
-        run: cargo nextest run --all-features
+        run: |
+          cargo nextest run --no-default-features --features static,dynamic
+          cargo nextest run --no-default-features --features static,dynamic,std
 
       - name: Test memvfs
         run: |
-          cargo build --example memvfs --features dynamic
+          cargo build --example memvfs --features dynamic,std
           cat examples/test_memvfs.sql | sqlite3
+          cat examples/test_memvfs_panic.sql | sqlite3 >/tmp/memvfs_panic 2>&1 \
+            || grep -q "unknown error (2)" /tmp/memvfs_panic
 
       - name: Clippy
         uses: auguwu/clippy-action@94a9ff2f6920180b89e5c03d121d0af04a9d3e03 # 1.4.0

Cargo.toml

@@ -29,8 +29,9 @@ bindgen = { version = "0.72", default-features = false }
 default = ["static"]
 static = []
 dynamic = []
+std = []
 
 [[example]]
 name = "memvfs"
 crate-type = ["cdylib"]
-required-features = ["dynamic"]
+required-features = ["dynamic", "std"]

examples/memvfs.rs

@@ -1,4 +1,4 @@
-// cargo build --example memvfs --features dynamic
+// cargo build --example memvfs --features dynamic,std
 
 use std::{ffi::c_void, os::raw::c_char, sync::Arc};
 
@@ -181,7 +181,11 @@ impl Vfs for MemVfs {
         pragma: Pragma<'_>,
     ) -> Result<Option<String>, PragmaErr> {
         log::debug!("pragma: file={:?}, pragma={:?}", handle.name, pragma);
-        Err(PragmaErr::NotFound)
+        if pragma.name == "memvfs_panic" {
+            panic!("testing panic")
+        } else {
+            Err(PragmaErr::NotFound)
+        }
     }
 }
 

examples/test_memvfs.sql

@@ -1,6 +1,6 @@
 -- Load the memvfs extension and open a new connection using it
 -- Build the memvfs extension using the following command:
---   cargo build --example memvfs --features dynamic
+--   cargo build --example memvfs --features dynamic,std
 
 -- uncomment to enable verbose logs
 -- .log stderr

examples/test_memvfs_panic.sql

@@ -0,0 +1,20 @@
+-- Load the memvfs extension and open a new connection using it
+-- Build the memvfs extension using the following command:
+--   cargo build --example memvfs --features dynamic,std
+
+-- uncomment to enable verbose logs
+-- .log stderr
+
+.load target/debug/examples/libmemvfs.so
+.open main.db
+.mode table
+.log stdout
+
+.databases
+.vfsinfo
+
+-- ensure that panics are handled
+pragma memvfs_panic;
+
+-- but they cause all future calls to also fail!
+CREATE TABLE t1(a, b);

src/lib.rs

@@ -1,4 +1,4 @@
-#![no_std]
+#![cfg_attr(not(feature = "std"), no_std)]
 extern crate alloc;
 
 pub mod vars {

src/vfs.rs

@@ -37,6 +37,9 @@ pub const DEFAULT_DEVICE_CHARACTERISTICS: i32 =
 /// A `SQLite3` extended error code
 pub type SqliteErr = i32;
 
+// construct a custom SQLITE_INTERNAL error code for tracking panics
+pub const ERROR_PANIC: SqliteErr = vars::SQLITE_INTERNAL | (128 << 8);
+
 pub type VfsResult<T> = Result<T, SqliteErr>;
 
 // FileWrapper needs to be repr(C) and have sqlite3_file as it's first member
@@ -79,6 +82,29 @@ impl PragmaErr {
     }
 }
 
+#[cfg(feature = "std")]
+fn fallible(mut cb: impl FnMut() -> Result<i32, SqliteErr>) -> i32 {
+    use std::sync::atomic::Ordering;
+    use std::{panic::AssertUnwindSafe, sync::atomic::AtomicBool};
+
+    // once we panic, all future calls into the VFS will also panic as we can't
+    // be sure that we are unwind safe
+    static POISONED: AtomicBool = AtomicBool::new(false);
+    if POISONED.load(Ordering::Relaxed) {
+        return ERROR_PANIC;
+    }
+
+    let inner = AssertUnwindSafe(|| cb().unwrap_or_else(|err| err));
+    match std::panic::catch_unwind(inner) {
+        Ok(i) => i,
+        Err(_err) => {
+            POISONED.store(true, Ordering::SeqCst);
+            ERROR_PANIC
+        }
+    }
+}
+
+#[cfg(not(feature = "std"))]
 fn fallible(mut cb: impl FnMut() -> Result<i32, SqliteErr>) -> i32 {
     cb().unwrap_or_else(|err| err)
 }