[UE4]Program Debugging Tricks Notes

Keywords: UE4, Programming Debug Tricks, Insights, Memory, Tracking, Profiling, Performance Optimization

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Shipping 版本开启log

添加以下到 Target.cs 的构造函数中（Editor.Target.cs不需要添加）：

BuildEnvironment = TargetBuildEnvironment.Unique;
bUseLoggingInShipping = true;

log文件生成位置

客户端log：%localappdata%\<ProjectName>\Saved\Logs；
服务端log：WindowsServer\<ProjectName>\Saved\Logs；

bUseLoggingInShipping = true;只对源码编译的引擎版本有效，Launcher版本无效。Launcher版本无法在Shipping模式下开启log。

VisualStudio中查看UE4 log

如果要查看VS命令行的UE4相关log，需要Debug模式（VS的Debug，即F5，不是UE4的DebugGame）

Android Device Monitor 打印log

比如UE4工程的C++代码中有如下log打印语句：

UE_LOG(LogTemp, Display, TEXT("aaaaaaa"));

我们希望这句话在Android Device Monitor中能也能够打印出来，默认情况下，需要在将设备的Config设置为DebugGame或者Development，Shipping下则不会打印。

Android Device Monitor中显示的游戏UE_LOG，统一都是Debug级别的蓝色，即使是UE_LOG的级别为Error，显示的也是蓝色。

Useful API

How to debug inline function?

Use FORCEINLINE_DEBUGGABLE.

Example:
from Engine\Source\Runtime\RHI\Public\RHICommandList.h:

FORCEINLINE_DEBUGGABLE void CopyTexture(FRHITexture* SourceTextureRHI, FRHITexture* DestTextureRHI, const FRHICopyTextureInfo& CopyInfo)
{
}

Setup:
Modify “Engine\Source\Runtime\Core\Public\Misc\CoreMiscDefines.h”:
Origin:

#if UE_BUILD_DEBUG
    #define FORCEINLINE_DEBUGGABLE FORCEINLINE_DEBUGGABLE_ACTUAL
#else
    #define FORCEINLINE_DEBUGGABLE FORCEINLINE
#endif

New:

#if UE_BUILD_DEBUG
    #define FORCEINLINE_DEBUGGABLE FORCEINLINE_DEBUGGABLE_ACTUAL
#else
    #if UE_BUILD_DEVELOPMENT
        #define FORCEINLINE_DEBUGGABLE FORCEINLINE_DEBUGGABLE_ACTUAL
    #else
        #define FORCEINLINE_DEBUGGABLE FORCEINLINE
    #endif
#endif

UE5: Disable code optimization for source block

UE_DISABLE_OPTIMIZATION

AMyActor::TestFun()
{
}

UE_ENABLE_OPTIMIZATION

How to print log in low level

FPlatformMisc::LowLevelOutputDebugStringf(TEXT("FWebBrowserTextureResource:CopySample 11"));

Trace & Insight

How to record tracing data for Insights

cpp code:

void UCharacterMovementComponent::TickComponent(float DeltaTime, enum ELevelTick TickType, FActorComponentTickFunction *ThisTickFunction)
{
    SCOPED_NAMED_EVENT(UCharacterMovementComponent_TickComponent, FColor::Yellow);
    SCOPE_CYCLE_COUNTER(STAT_CharacterMovement);
    SCOPE_CYCLE_COUNTER(STAT_CharacterMovementTick);
    CSV_SCOPED_TIMING_STAT_EXCLUSIVE(CharacterMovement);
    ...
}

Then start Engine\Binaries\Win64\Engine\Binaries\Win64\UnrealInsights.exe, then start application using CMD appending arguments:

MyGame.exe -trace=default,counters -statnamedevents

Profiling for remoted Insights:

TestServer.exe -tracehost=`your ip`

Q: How to enable Insights on Linux?
A: Add PLATFORM_LINUX in Engine\Source\Runtime\TraceLog\Public\Trace\Config.h.

SCOPE_CYCLE_COUNTER Usage

Take STAT_CharacterMovement for example:

Declare your Stat firstly (for more details, see: UE4\Engine\Source\Runtime\Engine\Public\EngineStats.h):
```
DECLARE_CYCLE_STAT_EXTERN(TEXT("Char Movement Total"), STAT_CharacterMovement, STATGROUP_Game, );
```
STATGROUP_Game means you can capture this counter using command stat game.
You can also add your customized stat command, such as STATGROUP_MYTEST.

Then add your Stat in your game source (see: CharacterMovementComponent.cpp):

void UCharacterMovementComponent::TickComponent()
{
    SCOPE_CYCLE_COUNTER(STAT_CharacterMovement);
    ...
}

Then profiling your game using Insights, flag counters must be appended.
```
MyGame.exe -trace=default,counters
```
Finally, you can view the counter in Insights.

You can also capture the counter from console command: stat game.

References:
https://blog.csdn.net/qq_29523119/article/details/123606732
https://blog.csdn.net/wmy19890322/article/details/131944569

How to print call stack in log

FDebug::DumpStackTraceToLog()

Origin:How to print callstack into log ?
https://answers.unrealengine.com/questions/446990/how-to-print-callstack-into-log.html

How to use Insights on Android

Using Insights on Android (UE4.24 or later)
https://qiita.com/EGJ-Takashi_Suzuki/items/4d586d73556995e3dd40

How to print performance issues log

Add define LOOKING_FOR_PERF_ISSUES.

Memory Profiling

Memory Optimization (Not recommended)

MallocLeakReporter Setup:

Add mactro in [Project].Target.cs:

 GlobalDefinitions.Add("MALLOC_LEAKDETECTION=1");

Ensure bIncludeDebugFile=TRUE in Project Settings.
Create a package with Development.

Execute command at runtime:

 mallocleak.start // Start tracing
 mallocleak.report // Get leak report
 mallocleak.stop // End of trace

MallocLeakReporter isn’t accurate, it’s just a reference.

MallocLeakReporter (MALLOC_LEAKDETECTION)
https://qiita.com/donbutsu17/items/7258955cbb458c1256c9

Debugging and Optimizing Memory
https://www.unrealengine.com/en-US/blog/debugging-and-optimizing-memory

Address Sanitizer (ASan)

modify Engine/Source/Program/UnrealBuildTool/Platform/<platform name>/UEBuild<platform name>.cs:

bEnableAddressSanitizer = true;

This option is usable on Linux and Mac only.

Reference: Enable Address Sanitizer in [UE4] and check for memory corruption
https://qiita.com/com04/items/feadbdc5651c1ffcf36a

Documents - Optimizing Memory