Disabling Error Checks in Release Builds

Error checking is indeed important, but there are good reasons to consider disabling some checks in release builds. Let's explore why:

Performance Considerations

The primary reason for disabling error checks in release builds is performance. Error checking often involves additional comparisons, function calls, or conditional branches.

While these operations are typically fast, they can add up in performance-critical sections of code that are executed frequently.

For example, consider our Render() function:

1void Image::Render(SDL_Surface* Surface) {
2#ifdef DEBUG
3  int InitialWidth = mAppliedDestRectangle.w;
4  int InitialHeight = mAppliedDestRectangle.h;
5#endif
6
7  if (mScalingMode == ScalingMode::None) {
8    SDL_BlitSurface(
9      mImageSurface, &mAppliedSrcRectangle,
10      Surface, &mAppliedDestRectangle);
11  } else {
12    SDL_BlitScaled(
13      mImageSurface, &mAppliedSrcRectangle,
14      Surface, &mAppliedDestRectangle);
15  }
16
17#ifdef DEBUG
18  if (InitialWidth != mAppliedDestRectangle.w) {
19    std::cout << "Horizontal clipping\n";
20  }
21  if (InitialHeight != mAppliedDestRectangle.h) {
22    std::cout << "Vertical clipping\n";
23  }
24#endif
25}

This function might be called many times per frame in a game. The debug checks, while useful during development, add overhead that isn't necessary in a well-tested release build.

Assumption of Correctness

In release builds, we often assume that our code has been thoroughly tested and that these checks are no longer necessary. This assumption allows us to optimize for the common case where errors don't occur.

Balancing Act

It's important to note that we're not advocating for removing all error checks. Critical checks that prevent crashes or data corruption should remain. The key is to find a balance between safety and performance.

Implementation Strategies

We can use preprocessor directives to selectively include or exclude error checks:

1void Image::SetSourceRectangle(
2  const SDL_Rect& Rect
3) {
4  mRequestedSrcRectangle = Rect;
5#ifdef DEBUG
6  if (!ValidateRectangle(
7    Rect, mImageSurface, "Source Rectangle"
8  )) {
9    std::cout << "Invalid source rectangle, "
10      "using default\n";
11  }
12#endif
13  mAppliedSrcRectangle = ValidateRectangle(
14    Rect, mImageSurface, "Source Rectangle"
15  ) ? Rect : SDL_Rect{
16    0, 0, mImageSurface->w, mImageSurface->h
17  };
18}

In this example, we keep the validation logic but only output debug information in debug builds.

Remember, the goal is to create a robust application that performs well. Use error checking judiciously, and consider the context of your application when deciding which checks to keep in release builds.