ci: install unixodbc-dev where the build links

odbc-sys links against libodbc/libodbcinst, so any job that links a binary
(cargo test, the cargo-fuzz targets, the cargo-test pre-commit hook) needs the
unixODBC dev libraries present. Restore the apt install in the unit-tests, fuzz,
and pre-commit jobs; Miri is unaffected because it interprets rather than links.

Also document the link-time dependency in README.md and AGENTS.md.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: maltesander

.github/workflows/build.yaml

@@ -20,6 +20,15 @@ jobs:
     name: Unit Tests
     runs-on: ubuntu-latest
     steps:
+      # odbc-sys links against libodbc/libodbcinst, so the unixODBC dev
+      # libraries must be present to link the test binaries (no running Driver
+      # Manager is needed — only the libraries).
+      - name: Install host dependencies
+        uses: awalsh128/cache-apt-pkgs-action@acb598e5ddbc6f68a970c5da0688d2f3a9f04d05 # v1.6.0
+        with:
+          packages: unixodbc-dev
+          version: ubuntu-latest
+
       - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
         with:
           persist-credentials: false
@@ -81,6 +90,13 @@ jobs:
     runs-on: ubuntu-latest
     needs: [unit-tests]
     steps:
+      # The fuzz binaries link stackable-odbc-core, which links libodbc.
+      - name: Install host dependencies
+        uses: awalsh128/cache-apt-pkgs-action@acb598e5ddbc6f68a970c5da0688d2f3a9f04d05 # v1.6.0
+        with:
+          packages: unixodbc-dev
+          version: ubuntu-latest
+
       - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
         with:
           persist-credentials: false

.github/workflows/pr_pre-commit.yaml

@@ -13,6 +13,13 @@ jobs:
   pre-commit:
     runs-on: ubuntu-latest
     steps:
+      # The cargo-test pre-commit hook links libodbc via odbc-sys.
+      - name: Install host dependencies
+        uses: awalsh128/cache-apt-pkgs-action@acb598e5ddbc6f68a970c5da0688d2f3a9f04d05 # v1.6.0
+        with:
+          packages: unixodbc-dev
+          version: ubuntu-latest
+
       - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
         with:
           persist-credentials: false

AGENTS.md

@@ -27,6 +27,10 @@ framework itself and, where relevant, how a downstream driver crate consumes it.
 - `tracing` for logging (not `println!` or `log`)
 - `#[repr(C)]` on all handle structs (required for tag-based validation)
 - `extern "system"` on all FFI exports (resolves to correct ABI on both Windows and Linux)
+- `odbc-sys` links against `libodbc`/`libodbcinst`, so building or testing needs
+  the unixODBC dev libraries installed (`unixodbc-dev` on Debian/Ubuntu). No DSN
+  or running Driver Manager is required. Miri is the exception — it interprets
+  rather than links, so it needs no system libraries.
 
 ### Changelog
 

README.md

@@ -55,10 +55,18 @@ When adding a new ODBC function to the framework later, add one entry to
 ## Testing
 
 ```bash
-cargo test           # unit tests (pure Rust, no Driver Manager needed)
+cargo test           # unit tests (no running Driver Manager needed)
 cargo bench          # Criterion fetch-throughput benchmark
 ```
 
+`stackable-odbc-core` links against unixODBC through
+[odbc-sys](https://github.com/pacman82/odbc-sys), so the dev libraries must be
+installed to build and test (no DSN or running Driver Manager is required):
+
+```bash
+sudo apt-get install unixodbc-dev   # Debian/Ubuntu
+```
+
 `stackable-odbc-core` holds all the raw-pointer marshalling, so it is checked by
 Miri (undefined behaviour + leaks) and cargo-fuzz (AddressSanitizer) on every PR: