genesys: Support printf-like messages in debug helper

backend/genesys_error.cc

@@ -44,6 +44,11 @@
 #define DEBUG_DECLARE_ONLY
 
 #include "genesys_error.h"
+#include <cstdarg>
+#include <cstdio>
+
+extern "C" void sanei_debug_msg(int level, int max_level, const char *be, const char *fmt,
+                                va_list ap);
 
 #if (defined(__GNUC__) || defined(__CLANG__)) && (defined(__linux__) || defined(__APPLE__))
 extern "C" char* __cxa_get_globals();
@@ -68,18 +73,43 @@ DebugMessageHelper::DebugMessageHelper(const char* func)
 {
     func_ = func;
     num_exceptions_on_enter_ = num_uncaught_exceptions();
-    DBG(DBG_proc, "%s: start", func_);
+    msg_[0] = '\0';
+    DBG(DBG_proc, "%s: start\n", func_);
 }
 
+DebugMessageHelper::DebugMessageHelper(const char* func, const char* format, ...)
+{
+    func_ = func;
+    num_exceptions_on_enter_ = num_uncaught_exceptions();
+    msg_[0] = '\0';
+    DBG(DBG_proc, "%s: start\n", func_);
+    DBG(DBG_proc, "%s: ", func_);
+
+    std::va_list args;
+    va_start(args, format);
+    sanei_debug_msg(DBG_proc, DBG_LEVEL, STRINGIFY(BACKEND_NAME), format, args);
+    va_end(args);
+    DBG(DBG_proc, "\n");
+}
+
+
 DebugMessageHelper::~DebugMessageHelper()
 {
     if (num_exceptions_on_enter_ < num_uncaught_exceptions()) {
-        if (status_) {
-            DBG(DBG_error, "%s: failed during %s", func_, status_);
+        if (msg_[0] != '\0') {
+            DBG(DBG_error, "%s: failed during %s\n", func_, msg_);
         } else {
-            DBG(DBG_error, "%s: failed", func_);
+            DBG(DBG_error, "%s: failed\n", func_);
         }
     } else {
-        DBG(DBG_proc, "%s: completed", func_);
+        DBG(DBG_proc, "%s: completed\n", func_);
     }
 }
+
+void DebugMessageHelper::vstatus(const char* format, ...)
+{
+    std::va_list args;
+    va_start(args, format);
+    std::vsnprintf(msg_, MAX_BUF_SIZE, format, args);
+    va_end(args);
+}

backend/genesys_error.h

@@ -129,19 +129,34 @@ private:
 
 class DebugMessageHelper {
 public:
+    static constexpr unsigned MAX_BUF_SIZE = 120;
+
     DebugMessageHelper(const char* func);
+    DebugMessageHelper(const char* func, const char* format, ...)
+    #ifdef __GNUC__
+        __attribute__((format(printf, 3, 4)))
+    #endif
+    ;
+
     ~DebugMessageHelper();
 
-    void status(const char* status) { status_ = status; }
-    void clear() { status_ = nullptr; }
+    void status(const char* msg) { vstatus("%s", msg); }
+    void vstatus(const char* format, ...)
+    #ifdef __GNUC__
+        __attribute__((format(printf, 2, 3)))
+    #endif
+    ;
+
+    void clear() { msg_[0] = '\n'; }
 
 private:
     const char* func_ = nullptr;
-    const char* status_ = nullptr;
+    char msg_[MAX_BUF_SIZE];
     unsigned num_exceptions_on_enter_ = 0;
 };
 
 #define DBG_HELPER(var) DebugMessageHelper var(__func__)
+#define DBG_HELPER_ARGS(var, ...) DebugMessageHelper var(__func__, __VA_ARGS__)
 
 template<class F>
 SANE_Status wrap_exceptions_to_status_code(const char* func, F&& function)