Index: ps/trunk/source/ps/CStr.cpp
===================================================================
--- ps/trunk/source/ps/CStr.cpp
+++ ps/trunk/source/ps/CStr.cpp
@@ -1,4 +1,4 @@
-/* Copyright (C) 2014 Wildfire Games.
+/* Copyright (C) 2019 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -31,6 +31,7 @@
 #include "lib/byte_order.h"
 #include "network/Serialization.h"
 
+#include <cctype>
 #include <iomanip>
 #include <sstream>
 
@@ -154,10 +155,24 @@
 	return ret;
 }
 
+/**
+ * libc++ and libstd++ differ on how they handle string-to-number parsing for floating-points numbers.
+ * See https://trac.wildfiregames.com/ticket/2780#comment:4 for details.
+ * To prevent this, only consider [0-9.-+], replace the others in-place with a neutral character.
+ */
+CStr ParseableAsNumber(CStr cleaned_copy)
+{
+	for (tchar& c : cleaned_copy)
+		if (!std::isdigit(c) && c != '.' && c != '-' && c != '+')
+			c = ' ';
+
+	return cleaned_copy;
+}
+
 float CStr::ToFloat() const
 {
 	float ret = 0;
-	std::tstringstream str(*this);
+	std::tstringstream str(ParseableAsNumber(*this));
 	str >> ret;
 	return ret;
 }
@@ -165,7 +180,7 @@
 double CStr::ToDouble() const
 {
 	double ret = 0;
-	std::tstringstream str(*this);
+	std::tstringstream str(ParseableAsNumber(*this));
 	str >> ret;
 	return ret;
 }
Index: ps/trunk/source/ps/tests/test_CStr.h
===================================================================
--- ps/trunk/source/ps/tests/test_CStr.h
+++ ps/trunk/source/ps/tests/test_CStr.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2010 Wildfire Games.
+/* Copyright (C) 2019 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -123,21 +123,35 @@
 		TS_ASSERT_EQUALS(str1.ToLong(), 1);
 		TS_ASSERT_EQUALS(str1.ToULong(), 1u);
 
-		CStr8 str2("bogus");
-		TS_ASSERT_EQUALS(str2.ToFloat(), 0.0f);
-		TS_ASSERT_EQUALS(str2.ToDouble(), 0.0);
-		TS_ASSERT_EQUALS(str2.ToInt(), 0);
-		TS_ASSERT_EQUALS(str2.ToUInt(), 0u);
-		TS_ASSERT_EQUALS(str2.ToLong(), 0);
-		TS_ASSERT_EQUALS(str2.ToULong(), 0u);
-
-		CStr8 str3("3bogus");
-		TS_ASSERT_EQUALS(str3.ToFloat(), 3.0f);
-		TS_ASSERT_EQUALS(str3.ToDouble(), 3.0);
-		TS_ASSERT_EQUALS(str3.ToInt(), 3);
-		TS_ASSERT_EQUALS(str3.ToUInt(), 3u);
-		TS_ASSERT_EQUALS(str3.ToLong(), 3);
-		TS_ASSERT_EQUALS(str3.ToULong(), 3u);
+		CStr8 str2("+1,234");
+		TS_ASSERT_DELTA(str2.ToFloat(), 1.f, 0.0001f);
+		TS_ASSERT_DELTA(str2.ToDouble(), 1., 0.0001);
+		TS_ASSERT_EQUALS(str2.ToInt(), 1);
+		TS_ASSERT_EQUALS(str2.ToUInt(), 1u);
+		TS_ASSERT_EQUALS(str2.ToLong(), 1);
+		TS_ASSERT_EQUALS(str2.ToULong(), 1u);
+
+		CStr8 str3("bogus");
+		TS_ASSERT_EQUALS(str3.ToFloat(), 0.0f);
+		TS_ASSERT_EQUALS(str3.ToDouble(), 0.0);
+		TS_ASSERT_EQUALS(str3.ToInt(), 0);
+		TS_ASSERT_EQUALS(str3.ToUInt(), 0u);
+		TS_ASSERT_EQUALS(str3.ToLong(), 0);
+		TS_ASSERT_EQUALS(str3.ToULong(), 0u);
+
+		CStr8 str4("3bogus");
+		TS_ASSERT_DELTA(str4.ToFloat(), 3.0f, 0.0001f);
+		TS_ASSERT_DELTA(str4.ToDouble(), 3.0, 0.0001);
+		TS_ASSERT_EQUALS(str4.ToInt(), 3);
+		TS_ASSERT_EQUALS(str4.ToUInt(), 3u);
+		TS_ASSERT_EQUALS(str4.ToLong(), 3);
+		TS_ASSERT_EQUALS(str4.ToULong(), 3u);
+
+		CStr8 str5("-3bogus");
+		TS_ASSERT_DELTA(str5.ToFloat(), -3.0f, 0.0001f);
+		TS_ASSERT_DELTA(str5.ToDouble(), -3.0, 0.0001);
+		TS_ASSERT_EQUALS(str5.ToInt(), -3);
+		TS_ASSERT_EQUALS(str5.ToLong(), -3);
 
 		setlocale(LC_NUMERIC, old);
 	}