`SQLite: query!()` segfaults rustc when a column has no declared type

[msdrigg]

I have found these related issues/pull requests

• (Fix) Handle nullability of SQLite rowid alias columns #4088: (Fix) Handle nullability of SQLite rowid alias columns. This PR introduced the crash. It started requesting the declared-type out-param from sqlite3_table_column_metadata() and dereferencing it unconditionally.
• fix(sqlite): correctly infer nullability for INTEGER PRIMARY KEY in RETURNING #4323 / sqlite INSERT ... RETURNING queries incorrectly return nullable #4322: another regression from (Fix) Handle nullability of SQLite rowid alias columns #4088 (INTEGER PRIMARY KEY in RETURNING going back to Option). Different symptom.
• sqlx prepare fails with error "unsupported type NULL of column #2" #1979 and unsupported type NULL error only on my machine #3546: both report unsupported type NULL of column #N. That's the error you should get for a column with no declared type. Right now you get a SIGSEGV before the error can be produced.

Description

StatementHandle::column_nullable asks sqlite3_table_column_metadata() for a column's declared type and then calls CStr::from_ptr() on the result without checking for null:

let datatype = CStr::from_ptr(datatype);

SQLite sets that out-param to NULL when the column was declared with no type at all, which is legal:

CREATE TABLE users (device_id PRIMARY KEY, name TEXT);

So describing that table dereferences a null pointer and the process dies with SIGSEGV. Because the query!() family describes a live database during macro expansion, the process that dies is rustc itself:

error: rustc interrupted by SIGSEGV, printing backtrace
  2  core::ffi::c_str::CStr::from_ptr
  3  sqlx_sqlite::statement::handle::StatementHandle::column_nullable
  4  sqlx_sqlite::connection::describe::describe
  5  sqlx_sqlite::describe_blocking
  6  sqlx_macros_core::database::impls::...::describe_blocking
  7  sqlx_macros_core::query::expand_with

The practical effect is that a crate can't be compiled online or run cargo sqlx prepare at all if any table in the database has an untyped column, even when no query touches that table. An existing .sqlx cache keeps working, so offline builds are unaffected, but the cache can't be regenerated.

This is a regression in 0.9.0. Before #4088 the declared-type slot was passed as ptr::null_mut() and never read.

The sibling function column_decltype, twenty lines up, already null-checks the equivalent pointer from sqlite3_column_decltype().

Reproduction steps

cargo new sqlx-repro && cd sqlx-repro
cargo add tokio --features macros,rt-multi-thread
cargo add sqlx@0.9.0 --no-default-features --features runtime-tokio,sqlite,macros

sqlite3 repro.db "CREATE TABLE users (device_id PRIMARY KEY, name TEXT);"

src/main.rs:

#[tokio::main]
async fn main() {
    let pool = sqlx::SqlitePool::connect(&std::env::var("DATABASE_URL").unwrap())
        .await
        .unwrap();
    let row = sqlx::query!("SELECT device_id, name FROM users")
        .fetch_optional(&pool)
        .await
        .unwrap();
    println!("{:?}", row.map(|r| r.name));
}

DATABASE_URL="sqlite://repro.db" cargo build

Crashes with signal: 11, SIGSEGV. Changing device_id PRIMARY KEY to device_id TEXT PRIMARY KEY and rebuilding makes it compile, which isolates the untyped column as the trigger.

SQLx version

0.9.0

Enabled SQLx features

runtime-tokio, sqlite, macros (with default-features = false) is enough to reproduce

Database server and version

SQLite 3.51.3

Operating system

macOS

Rust version

rustc 1.96.1 (31fca3adb 2026-06-26)