Made online change work on ur20

component-source/component/CmpFrame.c

@@ -1,3 +1,7 @@
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+#include "atmb_boot_link.h"
 #include "../src/atom_bridge.h"
 /*****************************************************************************
 *	Copyright:		Copyright CODESYS Development GmbH
@@ -38,6 +42,9 @@ DLL_DECL int CDECL ComponentEntry(INIT_STRUCT *pInitStruct)
 	s_pfCMCallHook = pInitStruct->pfCMCallHook;
 	s_pfCMRegisterClass = pInitStruct->pfCMRegisterClass;
 	s_pfCMCreateInstance = pInitStruct->pfCMCreateInstance;
+
+	/* Best effort only: never make component startup depend on this. */
+	atmb_ensure_boot_link();
 	return ERR_OK;
 }
 

component-source/component/atmb_boot_link.h

@@ -0,0 +1,109 @@
+#ifndef ATMB_BOOT_LINK_H
+#define ATMB_BOOT_LINK_H
+
+/* Linux-only boot-project pathname workaround. Include in CmpFrame.c only,
+ * with _GNU_SOURCE defined before all system headers.
+ * No PLC memory, communication state, worker thread or cyclic work is involved.
+ */
+#include <dlfcn.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <syslog.h>
+#include <unistd.h>
+#include <stdint.h>
+
+static void atmb_ensure_boot_link(void)
+{
+    /* ComponentEntry is called at module initialization, not on each scan.
+     * Guard against repeated entry; failure is deliberately not retried.
+     */
+    static int attempted;
+    const char *name = "libCmpAtomModbus.so";
+    const char *problem = NULL;
+    Dl_info info;
+    struct stat source, existing;
+    char *module_path = NULL;
+    int directory = -1;
+    int error = 0;
+    int saved_errno = errno;
+
+    if (attempted)
+        return;
+    attempted = 1;
+
+    /* The component function address identifies this loaded ELF object. Using
+     * code rather than a local data symbol also works with runtimes that do not
+     * expose local data addresses through dladdr().
+     */
+    if (!dladdr((void *)(uintptr_t)&atmb_ensure_boot_link, &info) || !info.dli_fname) {
+        problem = "cannot locate loaded module";
+        goto finish;
+    }
+    module_path = realpath(info.dli_fname, NULL);
+    if (!module_path) {
+        error = errno;
+        problem = "cannot resolve loaded module pathname";
+        goto finish;
+    }
+    if (stat(module_path, &source) != 0) {
+        error = errno;
+        problem = "cannot inspect loaded module file";
+        goto finish;
+    }
+    if (!S_ISREG(source.st_mode)) {
+        problem = "loaded module pathname is not a regular file";
+        goto finish;
+    }
+
+    /* Boot creation was observed looking up the bare filename relative to
+     * runtime cwd. Anchor this directory with an FD; never change cwd.
+     */
+    directory = open(".", O_RDONLY | O_DIRECTORY | O_CLOEXEC);
+    if (directory < 0) {
+        error = errno;
+        problem = "cannot open runtime working directory";
+        goto finish;
+    }
+    if (fstatat(directory, name, &existing, AT_SYMLINK_NOFOLLOW) == 0) {
+        struct stat resolved;
+        if (fstatat(directory, name, &resolved, 0) == 0 &&
+            resolved.st_dev == source.st_dev &&
+            resolved.st_ino == source.st_ino)
+            goto finish; /* Correct link, hard link, or the source itself. */
+        problem = "existing file or link left untouched; check boot-project path";
+        goto finish;
+    }
+    if (errno != ENOENT) {
+        error = errno;
+        problem = "cannot inspect boot-project pathname";
+        goto finish;
+    }
+
+    /* symlinkat fails on EEXIST: even a concurrent creator cannot be replaced.
+     * Keep this link on shutdown; boot-project creation may still need it.
+     */
+    if (symlinkat(module_path, directory, name) != 0) {
+        error = errno;
+        problem = "cannot create boot-project link";
+        goto finish;
+    }
+    syslog(LOG_INFO, "CmpAtomModbus: created boot link %s -> %s in runtime cwd",
+           name, module_path);
+
+finish:
+    if (problem) {
+        if (error)
+            syslog(LOG_WARNING, "CmpAtomModbus: %s: %s (errno=%d); Modbus startup continues",
+                   problem, strerror(error), error);
+        else
+            syslog(LOG_WARNING, "CmpAtomModbus: %s; Modbus startup continues", problem);
+    }
+    if (directory >= 0)
+        close(directory);
+    free(module_path);
+    errno = saved_errno;
+}
+#endif

component-source/component/makefile

@@ -1,8 +1,8 @@
 # Generated from supplied ExtensionSDK; build with target Linux toolchain.
 SDKDIR ?= ../../ExtensionSDK
 MAJORVER=0
-MINORVER=4
-CMPVERSION=0x00050000
+MINORVER=5
+CMPVERSION=0x00050001
 # Local development ID; check no other component uses this ID.
 CMPID=0x2001
 DOS2UNIX=dos2unix
@@ -10,4 +10,9 @@ M4=m4
 CC ?= gcc
 # The SDK otherwise includes CmpFrame in its component identity wildcard.
 override CSRC := CmpAtomModbus.c
+# dladdr locates this module; -ldl also supports glibc older than 2.34.
+LDLIBS += -ldl
 include $(SDKDIR)/makefile
+
+# Recompile the startup hook when the link helper changes.
+$(OUTDIR)/CmpFrame.o: atmb_boot_link.h

library/CmpAtomModbus.~u

@@ -0,0 +1,4 @@
+atom
+ADAM-CODESYS
+4648
+639270284382256389

tests/test_boot_link.py

@@ -0,0 +1,92 @@
+#!/usr/bin/env python3
+"""Linux host integration tests for the real dladdr/symlinkat helper; needs cc."""
+import ctypes
+import os
+from pathlib import Path
+import subprocess
+import sys
+import tempfile
+
+HEADER = Path(__file__).resolve().parents[1] / 'component-source/component'
+CASES = ['missing', 'correct', 'file', 'wrong_link', 'dangling', 'same_directory', 'unwritable', 'missing_source']
+
+def child(case, base):
+    base = Path(base)
+    module = base / 'PlcLogic/libCmpAtomModbus.so'
+    lib = ctypes.CDLL(str(module), use_errno=True)
+    lib.warning_count.restype = ctypes.c_int
+    lib.info_count.restype = ctypes.c_int
+    os.chdir(base)
+    link = base / 'libCmpAtomModbus.so'
+    if case == 'correct':
+        link.symlink_to('PlcLogic/libCmpAtomModbus.so')
+    elif case == 'file':
+        link.write_text('do not replace me')
+    elif case in ('wrong_link', 'dangling'):
+        if case == 'wrong_link':
+            (base / 'other').write_text('other file')
+        link.symlink_to('other')
+    elif case == 'same_directory':
+        os.chdir(module.parent)
+    elif case == 'missing_source':
+        module.unlink()
+    elif case == 'unwritable':
+        # sysfs cannot accept arbitrary regular symlinks, even as root.
+        os.chdir('/sys')
+        link = Path('/sys/libCmpAtomModbus.so')
+        assert not os.path.lexists(link)
+    ctypes.set_errno(123)
+    lib.run_check()
+    assert ctypes.get_errno() == 123, 'caller errno changed'
+    warnings = lib.warning_count()
+    infos = lib.info_count()
+    lib.run_check()
+    assert (warnings, infos) == (lib.warning_count(), lib.info_count()), 'retried or logged twice'
+    if case == 'missing':
+        assert link.is_symlink() and link.resolve() == module
+        assert (warnings, infos) == (0, 1)
+    elif case == 'correct':
+        assert os.readlink(link) == 'PlcLogic/libCmpAtomModbus.so'
+        assert (warnings, infos) == (0, 0)
+    elif case == 'same_directory':
+        assert module.is_file() and not module.is_symlink()
+        assert (warnings, infos) == (0, 0)
+    else:
+        assert (warnings, infos) == (1, 0)
+        if case == 'file':
+            assert link.read_text() == 'do not replace me'
+        elif case in ('wrong_link', 'dangling'):
+            assert os.readlink(link) == 'other'
+        else:
+            assert not os.path.lexists(link)
+    print('PASS', case)
+
+if len(sys.argv) == 3:
+    child(sys.argv[1], sys.argv[2])
+else:
+    with tempfile.TemporaryDirectory(prefix='atmb-link-test-') as temp:
+        root = Path(temp)
+        root.chmod(0o755)
+        harness = root / 'harness.c'
+        harness.write_text('''#define _GNU_SOURCE
+#define syslog test_syslog
+#include "atmb_boot_link.h"
+static int warnings, infos;
+void test_syslog(int priority, const char *format, ...) {
+    (void)format;
+    if (priority == LOG_WARNING) ++warnings;
+    if (priority == LOG_INFO) ++infos;
+}
+void run_check(void) { atmb_ensure_boot_link(); }
+int warning_count(void) { return warnings; }
+int info_count(void) { return infos; }
+''')
+        output = root / 'test.so'
+        subprocess.run([os.environ.get('CC', 'cc'), '-std=c99', '-Wall', '-Wextra', '-Werror',
+                        '-fPIC', '-shared', '-I', str(HEADER), str(harness), '-ldl', '-o', str(output)], check=True)
+        for case in CASES:
+            base = root / case
+            (base / 'PlcLogic').mkdir(parents=True)
+            (base / 'PlcLogic/libCmpAtomModbus.so').write_bytes(output.read_bytes())
+            subprocess.run([sys.executable, __file__, case, str(base)], check=True)
+            base.chmod(0o755)