Use a common base for a couple exceptions

al/filter.cpp

@@ -47,33 +47,17 @@
 
 namespace {
 
-class filter_exception final : public std::exception {
-    std::string mMessage;
-    ALenum mErrorCode;
-
+class filter_exception final : public al::base_exception {
 public:
-    filter_exception(ALenum code, const char *msg, ...) ALEXCPT_FORMAT(printf, 3,4);
-
-    const char *what() const noexcept override { return mMessage.c_str(); }
-    ALenum errorCode() const noexcept { return mErrorCode; }
-};
-
-filter_exception::filter_exception(ALenum code, const char *msg, ...) : mErrorCode{code}
-{
-    std::va_list args, args2;
-    va_start(args, msg);
-    va_copy(args2, args);
-    int msglen{std::vsnprintf(nullptr, 0, msg, args)};
-    if LIKELY(msglen > 0)
+    [[gnu::format(printf, 3, 4)]]
+    filter_exception(ALenum code, const char *msg, ...) : base_exception{code}
     {
-        mMessage.resize(static_cast<size_t>(msglen)+1);
-        std::vsnprintf(&mMessage[0], mMessage.length(), msg, args2);
-        mMessage.pop_back();
+        va_list args;
+        va_start(args, msg);
+        setMessage(msg, args);
+        va_end(args);
     }
-    va_end(args2);
-    va_end(args);
-}
-
+};
 
 #define FILTER_MIN_GAIN 0.0f
 #define FILTER_MAX_GAIN 4.0f /* +12dB */

alc/backends/base.h

@@ -8,8 +8,9 @@
 
 #include "AL/alc.h"
 
-#include "alcmain.h"
 #include "albyte.h"
+#include "alcmain.h"
+#include "alexcpt.h"
 
 
 struct ClockLatency {
@@ -79,4 +80,20 @@ protected:
     virtual ~BackendFactory() = default;
 };
 
+namespace al {
+
+class backend_exception final : public base_exception {
+public:
+    [[gnu::format(printf, 3, 4)]]
+    backend_exception(ALCenum code, const char *msg, ...) : base_exception{code}
+    {
+        std::va_list args;
+        va_start(args, msg);
+        setMessage(msg, args);
+        va_end(args);
+    }
+};
+
+} // namespace al
+
 #endif /* ALC_BACKENDS_BASE_H */

common/alexcpt.cpp

@@ -11,10 +11,9 @@
 
 namespace al {
 
-backend_exception::backend_exception(ALCenum code, const char *msg, ...) : mErrorCode{code}
+void base_exception::setMessage(const char* msg, std::va_list args)
 {
-    va_list args, args2;
-    va_start(args, msg);
+    std::va_list args2;
     va_copy(args2, args);
     int msglen{std::vsnprintf(nullptr, 0, msg, args)};
     if LIKELY(msglen > 0)
@@ -24,7 +23,6 @@ backend_exception::backend_exception(ALCenum code, const char *msg, ...) : mErro
         mMessage.pop_back();
     }
     va_end(args2);
-    va_end(args);
 }
 
 } // namespace al

common/alexcpt.h

@@ -1,28 +1,26 @@
 #ifndef ALEXCPT_H
 #define ALEXCPT_H
 
+#include <cstdarg>
 #include <exception>
 #include <string>
+#include <utility>
 
 #include "AL/alc.h"
 
 
-#ifdef __GNUC__
-#define ALEXCPT_FORMAT(x, y, z) __attribute__((format(x, (y), (z))))
-#else
-#define ALEXCPT_FORMAT(x, y, z)
-#endif
-
-
 namespace al {
 
-class backend_exception final : public std::exception {
+class base_exception : public std::exception {
     std::string mMessage;
     ALCenum mErrorCode;
 
-public:
-    backend_exception(ALCenum code, const char *msg, ...) ALEXCPT_FORMAT(printf, 3,4);
+protected:
+    base_exception(ALCenum code) : mErrorCode{code} { }
 
+    void setMessage(const char *msg, std::va_list args);
+
+public:
     const char *what() const noexcept override { return mMessage.c_str(); }
     ALCenum errorCode() const noexcept { return mErrorCode; }
 };