feat: ODBC-backed table driver (read + write) behind the ACE ABI (builds on #18)

CMakeLists.txt

@@ -68,6 +68,12 @@ option(OPENADS_WITH_TLS "Enable TLS transport (vendors mbedtls 3.6 LTS via Fetch
 # and nlohmann/json (MIT) at configure time via FetchContent.
 option(OPENADS_WITH_HTTP "Enable embedded HTTP web console (Studio) in openads_serverd / ace64.dll" ON)
 
+# Optional ODBC table driver. Talks to any data source through the
+# system ODBC driver manager (odbc32 on Windows, unixODBC on Linux);
+# the headers and import library ship with the platform SDK, so no
+# external dependency is downloaded. OFF by default.
+option(OPENADS_WITH_ODBC "Enable ODBC-backed table driver (system ODBC driver manager)" OFF)
+
 # Pull in mbedtls FIRST so our strict /WX -Werror flags don't bleed
 # into the upstream sources (C4200 zero-sized arrays etc). Each
 # OpenADS target adds the strict flags target-locally below via

docs/openads-plus/ODBC_LIVE_TARGETS.md

@@ -0,0 +1,37 @@
+# ODBC backend — verified live targets
+
+The ODBC Plus backend (`odbc://`) is data-source agnostic: it reaches any
+engine through its ODBC driver using only standard catalog calls
+(`SQLPrimaryKeys` / `SQLStatistics` / `SQLColumns`) and portable SQL. No
+per-dialect code lives in the backend.
+
+The same ABI test cases (`--test-case=*odbc*`) run against any target by
+pointing `OPENADS_TEST_ODBC_CONNSTR` at it. Two reproducible harnesses ship:
+
+| Target | Harness | Notes |
+|--------|---------|-------|
+| Microsoft Access (`.accdb`) | `tools/scripts/run_odbc_tests.ps1` | Zero-server; ADOX fixture, available out of the box on Windows. |
+| SQL Server / PostgreSQL / MariaDB / Firebird | `tools/scripts/run_odbc_tests_live.ps1 -ConnStr '...'` | Connection-string driven; seeds the `clientes` fixture over ODBC. |
+
+## Verified
+
+- **Microsoft Access** — 5 cases / 83 assertions (CI fixture).
+- **SQL Server 2022** — 5 cases / 83 assertions, via the *ODBC Driver 18 for
+  SQL Server*. The unmodified backend (same binary that passes against
+  Access) navigates a `dbo.clientes` table by primary key with no
+  dialect-specific changes: `SQLPrimaryKeys` is honoured, the identifier
+  quote character is discovered via `SQLGetInfo`, and numeric literals are
+  emitted type-aware.
+
+Both read navigation (`GO TOP` / `SKIP` / `SEEK`) and navigational write
+(`AdsAppendRecord` → `AdsSetString`/`AdsSetDouble` → `AdsWriteRecord`,
+plus `AdsDeleteRecord`) are exercised against the same fixture on both
+drivers. Write stages field values and flushes one `INSERT` (append) or
+`UPDATE` (positioned edit) per record; `AdsDeleteRecord` issues a `DELETE`
+by primary key. v1 expects the caller to supply the primary key on append
+(no IDENTITY round-trip yet) and emits SQL literals (parameter binding is a
+later hardening slice).
+
+When `OPENADS_TEST_ODBC_CONNSTR` is unset, the live cases skip (the backend
+is still exercised by the URI-parsing unit tests), so the suite stays green
+on machines without a configured data source.

src/CMakeLists.txt

@@ -58,6 +58,15 @@ add_library(openads_core STATIC
     network/mg_wire.cpp
 )
 
+if(OPENADS_WITH_ODBC)
+    target_sources(openads_core PRIVATE
+        sql_backend/sql_common.cpp
+        sql_backend/odbc_uri.cpp
+        sql_backend/odbc_backend.cpp
+        sql_backend/odbc_connection.cpp
+    )
+endif()
+
 if(WIN32)
     target_sources(openads_core PRIVATE
         platform/file_win32.cpp
@@ -98,6 +107,15 @@ if(OPENADS_WITH_TLS)
         MbedTLS::mbedtls MbedTLS::mbedx509 MbedTLS::mbedcrypto)
 endif()
 
+if(OPENADS_WITH_ODBC)
+    target_compile_definitions(openads_core PUBLIC OPENADS_WITH_ODBC=1)
+    if(WIN32)
+        target_link_libraries(openads_core PUBLIC odbc32)
+    else()
+        target_link_libraries(openads_core PUBLIC odbc)
+    endif()
+endif()
+
 # ----------------------------------------------------------------------
 # Drop-in replacement DLL: ace32.dll (x86) / ace64.dll (x64).
 # Harbour's contrib/rddads links against ace32.lib / ace64.lib import