Hide visibility of sinqController classes

README.md

@@ -310,3 +310,15 @@ If your driver uses another driver as a static dependency via git submodule whic
 - `git submodule update --init --recursive`
 
 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
+```

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

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

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