Export all symbols (#445)

Fixes #404 and effectively reverts most of #81.

After this lands we export:
* All C API symbols
* The Arrow ADBC entrypoint (`duckdb_adbc_init`)
* The Python extension entrypoint (`PyInit__duckdb`)
* Lots of mangled C++ symbols. This gives us better stacktraces again.

|  | Release build | Release wheel | Debug Build |
| -- | ------------- | --------------- | ------------ |
| **Size before** | 39.6 MB | 14 MB | 166 MB |
| **Size after** | 44.6 MB | 15 MB | 183 MB |

Author: evertlammerts

CMakeLists.txt

@@ -57,6 +57,11 @@ target_include_directories(
   INTERFACE $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/src/duckdb_py/include>
 )
 
+# We link duckdb_static. Without this define, duckdb.h marks C API symbols
+# __declspec(dllimport) on Windows, producing unresolvable __imp_* references at
+# link time. No-op on non-Windows.
+target_compile_definitions(_duckdb_dependencies INTERFACE DUCKDB_STATIC_BUILD)
+
 # ────────────────────────────────────────────
 # Descend into the real DuckDB‑Python sources
 # ────────────────────────────────────────────
@@ -81,37 +86,6 @@ pybind11_add_module(
 target_link_libraries(_duckdb PRIVATE _duckdb_dependencies)
 duckdb_link_extensions(_duckdb)
 
-# ────────────────────────────────────────────
-# Controlling symbol export
-#
-# We want to export exactly two symbols: - PyInit__duckdb: this allows CPython
-# to load the module - duckdb_adbc_init: the DuckDB ADBC driver
-#
-# The export of symbols on OSX and Linux is controlled by: - Visibility
-# annotations in the code (for this lib we use the PYBIND11_EXPORT macro) -
-# Telling the linker which symbols we want exported, which we do below
-#
-# For Windows, we rely on just the visbility annotations.
-# ────────────────────────────────────────────
-set_target_properties(
-  _duckdb
-  PROPERTIES CXX_VISIBILITY_PRESET hidden
-             C_VISIBILITY_PRESET hidden
-             VISIBILITY_INLINES_HIDDEN ON)
-
-if(APPLE)
-  target_link_options(
-    _duckdb PRIVATE "LINKER:-exported_symbol,_duckdb_adbc_init"
-    "LINKER:-exported_symbol,_PyInit__duckdb")
-elseif(UNIX AND NOT APPLE)
-  target_link_options(
-    _duckdb PRIVATE "LINKER:--export-dynamic-symbol=duckdb_adbc_init"
-    "LINKER:--export-dynamic-symbol=PyInit__duckdb")
-elseif(WIN32)
-  target_link_options(_duckdb PRIVATE "/EXPORT:duckdb_adbc_init"
-                      "/EXPORT:PyInit__duckdb")
-endif()
-
 # ────────────────────────────────────────────
 # Put the object file in the correct place
 # ────────────────────────────────────────────

src/duckdb_py/duckdb_python.cpp

@@ -1051,22 +1051,16 @@ static void RegisterExpectedResultType(py::handle &m) {
 }
 
 // ######################################################################
-// Symbol exports
+// Force inclusion of symbols that are not referenced by any code in the
+// Python module but must be present in the shared object.
 //
-// We want to limit the symbols we export to only the absolute minimum.
-// This means we compile with -fvisibility=hidden to hide all symbols,
-// and then explicitly export only the symbols we want.
+// duckdb_adbc_init: entrypoint for the ADBC driver. Not called from Python
+//   code, but loaded by adbc_driver_manager via dlsym/GetProcAddress.
 //
-// Right now we export two symbols only:
-// - duckdb_adbc_init: the entrypoint for our ADBC driver
-// - PyInit__duckdb: the entrypoint for the python extension
-//
-// All symbols that need exporting must be added to both the list below
-// AND to CMakeLists.txt.
+// Without this, the linker may strip these as dead code.
 extern "C" {
 PYBIND11_EXPORT void *_force_symbol_inclusion() {
 	static void *symbols[] = {
-	    // Add functions to export here
 	    (void *)&duckdb_adbc_init,
 	};
 	return symbols;