util/Error: use std::exception_ptr instead of std::exception

Necessary to preserve type information.  The try/catch sequence didn't
work previously.

Same fix as in commit 1c904000

src/db/plugins/simple/SimpleDatabasePlugin.cxx

@@ -222,7 +222,7 @@ try {
 
 	return true;
 } catch (const std::exception &e) {
-	error.Set(e);
+	error.Set(std::current_exception());
 	return false;
 }
 

src/input/plugins/FileInputPlugin.cxx

@@ -81,7 +81,7 @@ try {
 				   std::move(reader), info.GetSize(),
 				   mutex, cond);
 } catch (const std::exception &e) {
-	error.Set(e);
+	error.Set(std::current_exception());
 	return nullptr;
 }
 
@@ -102,7 +102,7 @@ try {
 	offset = new_offset;
 	return true;
 } catch (const std::exception &e) {
-	error.Set(e);
+	error.Set(std::current_exception());
 	return false;
 }
 
@@ -113,7 +113,7 @@ try {
 	offset += nbytes;
 	return nbytes;
 } catch (const std::exception &e) {
-	error.Set(e);
+	error.Set(std::current_exception());
 	return 0;
 }
 

src/util/Error.cxx

@@ -31,7 +31,6 @@
 #include "Error.hxx"
 #include "Domain.hxx"
 
-#include <exception>
 #include <system_error>
 
 #ifdef WIN32
@@ -54,11 +53,11 @@ const Domain win32_domain("win32");
 Error::~Error() {}
 
 void
-Error::Set(const std::exception &src)
+Error::Set(std::exception_ptr src)
 {
 	try {
 		/* classify the exception */
-		throw src;
+		std::rethrow_exception(src);
 	} catch (const std::system_error &se) {
 		if (se.code().category() == std::system_category()) {
 #ifdef WIN32
@@ -67,9 +66,11 @@ Error::Set(const std::exception &src)
 			Set(errno_domain, se.code().value(), se.what());
 #endif
 		} else
-			Set(exception_domain, src.what());
+			Set(exception_domain, se.what());
+	} catch (const std::exception &e) {
+		Set(exception_domain, e.what());
 	} catch (...) {
-		Set(exception_domain, src.what());
+		Set(exception_domain, "Unknown exception");
 	}
 }
 

src/util/Error.hxx

@@ -35,15 +35,12 @@
 
 #include <string>
 #include <utility>
+#include <exception>
 
 #include <assert.h>
 
 class Domain;
 
-namespace std {
-	class exception;
-}
-
 /** Domain for std::exception */
 extern const Domain exception_domain;
 
@@ -133,7 +130,7 @@ public:
 		message = other.message;
 	}
 
-	void Set(const std::exception &src);
+	void Set(std::exception_ptr src);
 
 	void Set(const Domain &_domain, int _code, const char *_message);