fix(native): pin clock_gettime to GLIBC_2.2.5 to keep glibc floor low

glibc 2.17 moved clock_gettime() into libc under a new GLIBC_2.17 version
node. Building the release .so in a modern container (manylinux_2_28) binds
clock_gettime@GLIBC_2.17, which raises the whole library's glibc floor to 2.17
and breaks loading on glibc 2.14-2.16 hosts.

Add src/main/c/share/glibc_compat.h with a .symver directive forcing the
reference back to clock_gettime@GLIBC_2.2.5 (x86-64 glibc only; no-op on
aarch64/macOS/Windows), include it from net.c and os.c, list it in the
CMake sources, and document the glibc floor in rebuild_native_libs.yml.

Author: bluestreak01

.github/workflows/rebuild_native_libs.yml

@@ -74,6 +74,13 @@ jobs:
     # inside the glibc-2.17 image (the old Node-20-glibc-217 override hack only
     # patched /__e/node20, not /__e/node24). 2.28 still runs stock Node 24 and
     # matches the linux-aarch64 job, which already ships glibc-2.28 binaries.
+    #
+    # NOTE: the build container's glibc (2.28) does NOT dictate the artifact's
+    # runtime glibc floor. clock_gettime is pinned back to GLIBC_2.2.5 via
+    # src/main/c/share/glibc_compat.h so the linux-x86-64 .so keeps loading on
+    # glibc 2.14+ (its floor is memcpy@GLIBC_2.14), unchanged from before the
+    # container move. If you add a symbol with a higher version node here, the
+    # floor will rise -- check with: objdump -T libquestdb.so | grep GLIBC_.
     container:
       image: quay.io/pypa/manylinux_2_28_x86_64
     steps:

core/CMakeLists.txt

@@ -48,6 +48,7 @@ set(
         src/main/c/share/files.h
         src/main/c/share/net.h
         src/main/c/share/os.h
+        src/main/c/share/glibc_compat.h
         src/main/c/share/ooo.cpp
         src/main/c/share/cpprt_overrides.h
         src/main/c/share/cpprt_overrides.cpp

core/src/main/c/share/glibc_compat.h

@@ -0,0 +1,53 @@
+/*+*****************************************************************************
+ *     ___                  _   ____  ____
+ *    / _ \ _   _  ___  ___| |_|  _ \| __ )
+ *   | | | | | | |/ _ \/ __| __| | | |  _ \
+ *   | |_| | |_| |  __/\__ \ |_| |_| | |_) |
+ *    \__\_\\__,_|\___||___/\__|____/|____/
+ *
+ *  Copyright (c) 2014-2019 Appsicle
+ *  Copyright (c) 2019-2026 QuestDB
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ ******************************************************************************/
+
+#ifndef QUESTDB_GLIBC_COMPAT_H
+#define QUESTDB_GLIBC_COMPAT_H
+
+// Pin clock_gettime() to its original GLIBC_2.2.5 symbol version.
+//
+// glibc 2.17 moved clock_gettime() out of librt and into libc, exporting it
+// under a NEW version node: clock_gettime@GLIBC_2.17. The release binaries are
+// built in a modern toolchain container (CI uses manylinux_2_28 / glibc 2.28),
+// so without this pin the linker binds our calls to clock_gettime@GLIBC_2.17.
+// That single symbol raises the whole library's glibc floor to 2.17 and makes
+// it fail to LOAD on hosts running glibc 2.14-2.16 with:
+//
+//     version `GLIBC_2.17' not found (required by libquestdb.so)
+//
+// The original clock_gettime@GLIBC_2.2.5 symbol is still exported as a compat
+// symbol by librt.so.1 on every glibc since (and by libc after the 2.34 librt
+// merge), so forcing the reference back to it keeps the library loadable down
+// to the previous floor (glibc 2.14, set by memcpy@GLIBC_2.14) with no change
+// in runtime behaviour. librt is already a NEEDED dependency (CMake links rt).
+//
+// Scope: x86-64 glibc only. aarch64 glibc started at 2.17 and has only ever
+// shipped clock_gettime in libc@GLIBC_2.17 -- there is no GLIBC_2.2.5 version
+// there, so emitting the pin on aarch64 would fail the link with an undefined
+// clock_gettime@GLIBC_2.2.5. The directive is a no-op on macOS/Windows.
+#if defined(__linux__) && defined(__GLIBC__) && defined(__x86_64__)
+__asm__(".symver clock_gettime,clock_gettime@GLIBC_2.2.5");
+#endif
+
+#endif // QUESTDB_GLIBC_COMPAT_H

core/src/main/c/share/net.c

@@ -35,6 +35,7 @@
 #include <string.h>
 #include <poll.h>
 #include <time.h>
+#include "glibc_compat.h"
 #include "net.h"
 #include <netdb.h>
 #include "sysutil.h"

core/src/main/c/share/os.c

@@ -30,6 +30,7 @@
 #include <string.h>
 #include <sys/time.h>
 #include <time.h>
+#include "glibc_compat.h"
 #include "../share/os.h"
 
 #ifdef __APPLE__