4 files changed, 48 insertions, 15 deletions
diff --git a/src/util/error.cpp b/src/util/error.cpp
index 9331a92ad..9edb7dc53 100644
--- a/src/util/error.cpp
+++ b/src/util/error.cpp
@@ -4,7 +4,9 @@
 
 #include <util/error.h>
 
+#include <tinyformat.h>
 #include <util/system.h>
+#include <util/translation.h>
 
 std::string TransactionErrorString(const TransactionError err)
 {
@@ -36,10 +38,10 @@ std::string TransactionErrorString(const TransactionError err)
 
 std::string AmountHighWarn(const std::string& optname)
 {
-    return strprintf(_("%s is set very high!"), optname);
+    return strprintf(_("%s is set very high!").translated, optname);
 }
 
 std::string AmountErrMsg(const char* const optname, const std::string& strValue)
 {
-    return strprintf(_("Invalid amount for -%s=<amount>: '%s'"), optname, strValue);
+    return strprintf(_("Invalid amount for -%s=<amount>: '%s'").translated, optname, strValue);
 }
diff --git a/src/util/system.cpp b/src/util/system.cpp
index 72b37b918..c27b0cc10 100644
--- a/src/util/system.cpp
+++ b/src/util/system.cpp
@@ -7,6 +7,7 @@
 
 #include <chainparamsbase.h>
 #include <util/strencodings.h>
+#include <util/translation.h>
 
 #include <stdarg.h>
 
@@ -1184,7 +1185,7 @@ int GetNumCores()
 
 std::string CopyrightHolders(const std::string& strPrefix)
 {
-    const auto copyright_devs = strprintf(_(COPYRIGHT_HOLDERS), COPYRIGHT_HOLDERS_SUBSTITUTION);
+    const auto copyright_devs = strprintf(_(COPYRIGHT_HOLDERS).translated, COPYRIGHT_HOLDERS_SUBSTITUTION);
     std::string strCopyrightHolders = strPrefix + copyright_devs;
 
     // Make sure Bitcoin Core copyright is not removed by accident
diff --git a/src/util/system.h b/src/util/system.h
index dda915648..66a9eb461 100644
--- a/src/util/system.h
+++ b/src/util/system.h
@@ -40,18 +40,6 @@ int64_t GetStartupTime();
 
 extern const char * const BITCOIN_CONF_FILENAME;
 
-/** Translate a message to the native language of the user. */
-const extern std::function<std::string(const char*)> G_TRANSLATION_FUN;
-
-/**
- * Translation function.
- * If no translation function is set, simply return the input.
- */
-inline std::string _(const char* psz)
-{
-    return G_TRANSLATION_FUN ? (G_TRANSLATION_FUN)(psz) : psz;
-}
-
 void SetupEnvironment();
 bool SetupNetworking();
 
diff --git a/src/util/translation.h b/src/util/translation.h
new file mode 100644
index 000000000..f100dab20
--- /dev/null
+++ b/src/util/translation.h
@@ -0,0 +1,42 @@
+// Copyright (c) 2019 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_TRANSLATION_H
+#define BITCOIN_UTIL_TRANSLATION_H
+
+#include <tinyformat.h>
+
+#include <utility>
+
+/**
+ * Bilingual messages:
+ *   - in GUI: user's native language + untranslated (i.e. English)
+ *   - in log and stderr: untranslated only
+ */
+struct bilingual_str {
+    std::string original;
+    std::string translated;
+};
+
+namespace tinyformat {
+template <typename... Args>
+bilingual_str format(const bilingual_str& fmt, const Args&... args)
+{
+    return bilingual_str{format(fmt.original, args...), format(fmt.translated, args...)};
+}
+} // namespace tinyformat
+
+/** Translate a message to the native language of the user. */
+const extern std::function<std::string(const char*)> G_TRANSLATION_FUN;
+
+/**
+ * Translation function.
+ * If no translation function is set, simply return the input.
+ */
+inline bilingual_str _(const char* psz)
+{
+    return bilingual_str{psz, G_TRANSLATION_FUN ? (G_TRANSLATION_FUN)(psz) : psz};
+}
+
+#endif // BITCOIN_UTIL_TRANSLATION_H