Debug Print C++ Reference

Write timestamped debug messages from C++ with SCOOTER_DEBUG_PRINT, DebugPrint, and LogMessage.

Header: DebugPrint.h · Class: USUDebugPrint

All three entry points produce the same message format and can append to a log file in your project's Saved/Logs folder. For the message format and an example of the output, see the Debug Print node.

Name	Description
SCOOTER_DEBUG_PRINT	printf-style macro that fills in the source file and line number as the context.
USUDebugPrint::DebugPrint	printf-style function with no context.
USUDebugPrint::LogMessage	FString version with an optional context. Also the Blueprint node.
EDebugLevel	The severity: sets the label in the message and the Output Log verbosity.

EDebugLevel

enum class EDebugLevel : uint8 { Info, Warning, Error, Critical };

Value	Label in the message	Output Log verbosity
EDebugLevel::Info	INFO	Log
EDebugLevel::Warning	WARNING	Warning
EDebugLevel::Error	ERROR	Error
EDebugLevel::Critical	CRITICAL	Error (never Fatal, so it doesn't stop the process)

SCOOTER_DEBUG_PRINT

SCOOTER_DEBUG_PRINT(LogFile, Level, Format, ...)

Formats a printf-style message and logs it, using the call site's file and line as the context:

LogDebugPrint: [2026.277.180002] D:\MyGame\Source\MyGame\MyCharacter.cpp:15: INFO: macro 42

Name	Description
LogFile	const TCHAR*. The log file to append to, relative to Saved/Logs. Pass TEXT("") to write only to the Output Log.
Level	EDebugLevel. The severity. See EDebugLevel.
Format	const TCHAR*. A printf-style format string, such as TEXT("Health: %d").
...	The values for Format.

Returns: bool, the same as LogMessage.

#include "DebugPrint.h"

void AMyCharacter::TakeHit(int32 Damage)
{
    Health -= Damage;
    SCOOTER_DEBUG_PRINT(TEXT("Combat.log"), EDebugLevel::Warning, TEXT("%s took %d damage, %d left"), *GetName(), Damage, Health);
}

DebugPrint

static bool USUDebugPrint::DebugPrint(const TCHAR* LogFile, EDebugLevel Level, const TCHAR* Format, ...);

Formats a printf-style message and logs it with no context. Takes the same parameters as SCOOTER_DEBUG_PRINT.

Returns: bool, the same as LogMessage.

USUDebugPrint::DebugPrint(TEXT(""), EDebugLevel::Info, TEXT("Loaded %d items"), Items.Num());

Output (no context):

LogDebugPrint: [2026.277.180002] INFO: Loaded 12 items

LogMessage

static bool USUDebugPrint::LogMessage(const FString& LogFile, EDebugLevel Level, const FString& Content, const FString& Context = TEXT(""));

Logs a message that's already been built. This is the function behind the Log Message Blueprint node, and the one the other two call after formatting.

Name	Description
LogFile	The log file to append to, relative to Saved/Logs. Example: MyGame.log or Debug/Testing.log. Pass an empty string to write only to the Output Log.
Level	The severity. See EDebugLevel.
Content	The message text. It isn't treated as a format string.
Context	Optional text that says where the message came from. When empty, it's left out along with its colon.

Returns: true if the message was logged. When LogFile is set, false means the file couldn't be written.

USUDebugPrint::LogMessage(TEXT("Multiplayer.log"), EDebugLevel::Info, TEXT("Player joined: ") + PlayerName, TEXT("Multiplayer"));

Output, in the Output Log and appended to Saved/Logs/Multiplayer.log:

LogDebugPrint: [2026.277.180002] Multiplayer: INFO: Player joined: Steve

Warnings and errors carry the Output Log's verbosity prefix:

LogDebugPrint: Warning: [2026.277.180002] WARNING: DebugPrint ok
LogDebugPrint: Error: [2026.277.180002] LinkTest: ERROR: LogMessage ok

Formatting Tips

• Pass FString values to the printf-style versions with *, like *GetName(). Passing an FString directly to ... is undefined behavior.
• The printf-style versions also take LogFile as a const TCHAR*, so use TEXT("MyGame.log") or *MyLogFileString.
• To log text that might contain a %, use TEXT("%s"), *Text rather than passing the text as Format, or call LogMessage.
• The printf-style versions handle messages of any practical length. Messages over about a million characters are truncated.

NOTE

SCOOTER_DEBUG_PRINT expands to a call to USUDebugPrint::DebugPrintInternal, which is public only so the macro can reach it. Use the macro instead of calling it directly.