fixed an access after free in OS_X11::set_context.

Added constructor and assignment operator for CharString
from const char* to simplify memory management when working with
utf8/ascii strings for APIs taking char*.
Reworked OS_X11::set_context to use CharString and avoid some manual
memory management.

3 files changed, 51 insertions, 15 deletions

diff --git a/core/ustring.cpp b/core/ustring.cpp
index d60bd16921..78feddb229 100644
--- a/core/ustring.cpp
+++ b/core/ustring.cpp
@@ -123,6 +123,31 @@ const char *CharString::get_data() const {
 		return "";
 }
 
+CharString &CharString::operator=(const char *p_cstr) {
+
+	copy_from(p_cstr);
+	return *this;
+}
+
+void CharString::copy_from(const char *p_cstr) {
+
+	if (!p_cstr) {
+		resize(0);
+		return;
+	}
+
+	size_t len = strlen(p_cstr);
+
+	if (len == 0) {
+		resize(0);
+		return;
+	}
+
+	resize(len + 1); // include terminating null char
+
+	strcpy(ptrw(), p_cstr);
+}
+
 void String::copy_from(const char *p_cstr) {
 
 	if (!p_cstr) {
diff --git a/core/ustring.h b/core/ustring.h
index 85103057df..e2e62874d6 100644
--- a/core/ustring.h
+++ b/core/ustring.h
@@ -101,12 +101,17 @@ public:
 		_cowdata._ref(p_str._cowdata);
 		return *this;
 	}
+	_FORCE_INLINE_ CharString(const char *p_cstr) { copy_from(p_cstr); }
 
+	CharString &operator=(const char *p_cstr);
 	bool operator<(const CharString &p_right) const;
 	CharString &operator+=(char p_char);
 	int length() const { return size() ? size() - 1 : 0; }
 	const char *get_data() const;
 	operator const char *() const { return get_data(); };
+
+protected:
+	void copy_from(const char *p_cstr);
 };
 
 typedef wchar_t CharType;
diff --git a/platform/x11/os_x11.cpp b/platform/x11/os_x11.cpp
index ad4bcb283f..f6161a9485 100644
--- a/platform/x11/os_x11.cpp
+++ b/platform/x11/os_x11.cpp
@@ -3036,34 +3036,40 @@ bool OS_X11::is_vsync_enabled() const {
 */
 void OS_X11::set_context(int p_context) {
 
-	char *config_name = NULL;
 	XClassHint *classHint = XAllocClassHint();
 
 	if (classHint) {
 
-		char *wm_class = (char *)"Godot";
-		if (p_context == CONTEXT_EDITOR)
-			classHint->res_name = (char *)"Godot_Editor";
-		if (p_context == CONTEXT_PROJECTMAN)
-			classHint->res_name = (char *)"Godot_ProjectList";
+		CharString name_str;
+		switch (p_context) {
+			case CONTEXT_EDITOR:
+				name_str = "Godot_Editor";
+				break;
+			case CONTEXT_PROJECTMAN:
+				name_str = "Godot_ProjectList";
+				break;
+			case CONTEXT_ENGINE:
+				name_str = "Godot_Engine";
+				break;
+		}
 
+		CharString class_str;
 		if (p_context == CONTEXT_ENGINE) {
-			classHint->res_name = (char *)"Godot_Engine";
-			String config_name_tmp = GLOBAL_GET("application/config/name");
-			if (config_name_tmp.length() > 0) {
-				config_name = strdup(config_name_tmp.utf8().get_data());
+			String config_name = GLOBAL_GET("application/config/name");
+			if (config_name.length() == 0) {
+				class_str = "Godot_Engine";
 			} else {
-				config_name = strdup("Godot Engine");
+				class_str = config_name.utf8();
 			}
-
-			wm_class = config_name;
+		} else {
+			class_str = "Godot";
 		}
 
-		classHint->res_class = wm_class;
+		classHint->res_class = class_str.ptrw();
+		classHint->res_name = name_str.ptrw();
 
 		XSetClassHint(x11_display, x11_window, classHint);
 		XFree(classHint);
-		free(config_name);
 	}
 }