Fix: panic musn't allocate error message string

src/crystal/system/panic.cr

@@ -1,19 +1,34 @@
 module Crystal::System
-  # Prints a system error message on the standard error then exits.
+  # Prints a system error message on the standard error then exits with an error
+  # status.
   #
   # Prefer `RuntimeError.from_os_error` unless you can't allocate any memory
   # (e.g. stop the world).
-  def self.panic(syscall_name : String, error = nil)
-    error ||=
-      {% if flag?(:unix) %}
-        Errno.value
-      {% elsif flag?(:win32) %}
-        WinError.value
-      {% else %}
-        {% raise "Unsupported target" %}
-      {% end %}
-    Crystal::System.print_error("%s failed with %s (%s)\n",
-      syscall_name, error.message, error.to_s)
-    exit 1
-  end
+  {% if flag?(:unix) %}
+    def self.panic(syscall_name : String, error : Errno = Errno.value) : NoReturn
+      buffer = LibC.strerror(error.value)
+      message = Bytes.new(buffer, LibC.strlen(buffer))
+      Crystal::System.print_error("%s failed with ", syscall_name)
+      Crystal::System.print_error(message)
+      Crystal::System.print_error(" (%s)\n", error.to_s)
+      exit 1
+    end
+  {% elsif flag?(:win32) %}
+    def self.panic(syscall_name : String, error : WinError = WinError.value) : NoReturn
+      buffer = uninitialized UInt16[256]
+      size = LibC.FormatMessageW(LibC::FORMAT_MESSAGE_FROM_SYSTEM, nil, error.value, 0, buffer, buffer.size, nil)
+      message = buffer.to_slice[0, size]
+      Crystal::System.print_error("%s failed with ", syscall_name)
+      Crystal::System.print_error(message)
+      Crystal::System.print_error(" (%s)\n", error.to_s)
+      exit 1
+    end
+  {% elsif flag?(:wasm32) %}
+    def self.panic(syscall_name : String, error : WasiError) : NoReturn
+      Crystal::System.print_error("%s failed with %s (%s)", syscall_name, error.message, error.to_s)
+      exit 1
+    end
+  {% else %}
+    {% raise "Unsupported target" %}
+  {% end %}
 end