From c19e4845e460c85d96cac15d6aa9e6bdcb4076a3 Mon Sep 17 00:00:00 2001
From: smathis <stefan.mathis@psi.ch>
Date: Tue, 12 Aug 2025 08:51:54 +0200
Subject: [PATCH] Hide visibility of sinqController classes

---
 README.md             | 14 +++++++++++++-
 src/msgPrintControl.h | 19 +++++++++++++++++--
 src/sinqAxis.h        |  3 ++-
 src/sinqController.h  |  4 ++--
 4 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/README.md b/README.md
index 2ff0644..ccc9a81 100644
--- a/README.md
+++ b/README.md
@@ -309,4 +309,16 @@ If your driver uses another driver as a static dependency via git submodule whic
 - `git commit -m "Update turboPmac to 1.0"`
 - `git submodule update --init --recursive`
 
-This will update sinqMotor to the version specified in the 1.0 commit of turboPmac.
\ No newline at end of file
+This will update sinqMotor to the version specified in the 1.0 commit of turboPmac.
+
+### Exporting symbols
+
+By default, the symbols of classes and functions are hidden to avoid symbol clashes when loading
+multiple shared libraries which use `sinqMotor`. In order to compile this library with exported
+symbols, specifiy `-DHIDDEN= ` as a compiler flag (if using the given Makefile, this
+needs to be added to the `USR_CFLAGS`).
+
+Derived libraries can use the same mechanism via the macro `HIDDEN` (defined in `msgPrintControl.h`):
+```
+class HIDDEN turboPmacController : public sinqController
+```
diff --git a/src/msgPrintControl.h b/src/msgPrintControl.h
index a228f8e..a52616c 100644
--- a/src/msgPrintControl.h
+++ b/src/msgPrintControl.h
@@ -10,12 +10,27 @@
 #include <string>
 #include <unordered_map>
 
+/*
+The macro "HIDDEN" hides the symbol of the annotated class / function. This is
+useful to avoid symbol clashes when loading multiple shared libraries in a
+single IOC. To override the hiding, add `-DHIDDEN= ` to your compiler
+flags (in this case, the symbols will be exported with their default
+visibility).
+*/
+#ifndef HIDDEN
+#if defined(_WIN32) || defined(__CYGWIN__)
+#define HIDDEN
+#else
+#define HIDDEN __attribute__((visibility("hidden")))
+#endif
+#endif
+
 /**
  * @brief Class to identify a message print location. See the docstring of
  * `msgPrintControl` on how to use this key.
  *
  */
-class msgPrintControlKey {
+class HIDDEN msgPrintControlKey {
   public:
     std::string controller_;
 
@@ -82,7 +97,7 @@ template <> struct hash<msgPrintControlKey> {
  * }
  * ```
  */
-class msgPrintControl {
+class HIDDEN msgPrintControl {
   public:
     /**
      * @brief Destroy the msgPrintControl object
diff --git a/src/sinqAxis.h b/src/sinqAxis.h
index b3b7ffe..3f90f76 100644
--- a/src/sinqAxis.h
+++ b/src/sinqAxis.h
@@ -9,12 +9,13 @@ Stefan Mathis, November 2024
 #ifndef sinqAxis_H
 #define sinqAxis_H
 #include "asynMotorAxis.h"
+#include "msgPrintControl.h"
 #include <memory>
 #include <type_traits>
 
 struct sinqAxisImpl;
 
-class epicsShareClass sinqAxis : public asynMotorAxis {
+class HIDDEN sinqAxis : public asynMotorAxis {
   public:
     /**
      * @brief Construct a new sinqAxis object
diff --git a/src/sinqController.h b/src/sinqController.h
index c12dd55..f359dd9 100644
--- a/src/sinqController.h
+++ b/src/sinqController.h
@@ -20,9 +20,9 @@ Stefan Mathis, November 2024
 #define AbsoluteEncoder "absolute"
 #define NoEncoder "none"
 
-struct sinqControllerImpl;
+struct HIDDEN sinqControllerImpl;
 
-class epicsShareClass sinqController : public asynMotorController {
+class HIDDEN sinqController : public asynMotorController {
   public:
     /**
    * @brief Construct a new sinqController object