SoapyAudio with USE_HAMLIB=1 fails to compile with Hamlib version >= 4.6

[n1ai]

I am compiling SoapyAudio with the current top-of-tree Hamlib which is 4.6-git.

In git blame for include/hamlib/rig.h we see that the first arg to rig_list_foreach() has gone from 'const int' to just 'int'.

This results in the error:

SoapyAudio/Registration.cpp:92:25: error: invalid conversion from ‘int (*)(const rig_caps*, void*)’ to ‘int (*)(rig_caps*, void*)’ [-fpermissive]
   92 |         rig_list_foreach(SoapyAudio::add_hamlib_rig, 0);
      |         ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |                         |
      |                         int (*)(const rig_caps*, void*)

The fix is easy, just get rid of 'const' in two places:

$ git diff | cat
diff --git a/Registration.cpp b/Registration.cpp
index 82a3452..dae1891 100644
--- a/Registration.cpp
+++ b/Registration.cpp
@@ -97,7 +97,7 @@ static std::vector<SoapySDR::Kwargs> findAudio(const SoapySDR::Kwargs &args)
 }
 
 #ifdef USE_HAMLIB
-int SoapyAudio::add_hamlib_rig(const struct rig_caps *rc, void* f)
+int SoapyAudio::add_hamlib_rig(struct rig_caps *rc, void* f)
 {
     rigCaps.push_back(rc);
 	return 1;
diff --git a/SoapyAudio.hpp b/SoapyAudio.hpp
index 6eefb76..1a68589 100644
--- a/SoapyAudio.hpp
+++ b/SoapyAudio.hpp
@@ -259,7 +259,7 @@ public:
 
 #ifdef USE_HAMLIB
 public:
-    static int add_hamlib_rig(const struct rig_caps *rc, void* f);
+    static int add_hamlib_rig(struct rig_caps *rc, void* f);
     static std::vector<const struct rig_caps *> rigCaps;
     
     void checkRigThread();

I will leave it up to the SoapyAudio maintainers as to when and how to fix this.

The compiler is hinting that '-fpermissive' would make this error go away.

Maybe that's the best way to handle it, either on the command line or in a directive in the source code, given that it's best to tolerate both old and new versions of hamlib.

Regards,
Dave, N1AI