Is the C++ debugging experience on VSCode supposed to be this slow?

General
1

I have a project that I’ve tried debugging in Windows with MSVC and on Linux with Clang and GCC. On Windows it’s very fast, like 10 times faster than the best I can get on Linux with CLion. But because I want to get used to working on Linux I’m trying different methods of doing this on Linux using:

VS Code
and
CLion

For some reason I try with both GCC and Clang on VSCode, and I’ve downloaded the C++ tools, and it’s very very slow in both running code and also starting the debugging, like I’m talking about 5 to 10 times slower than using CLion. With CLion I’ve used the GCC and Clang CMakePresets, and it’s much much faster than VSCode. I don’t understand this because the same compiler is being used, and the same debugger (I think), which is GDB. Is VSCode supposed to be this much slower? Is it conceivable for there to be a fivefold performance degradation just from choice of IDE (ie., VSCode or CLion)?

2

You’re right to be surprised — a 5–10x slowdown in debugging or execution performance shouldn’t happen just because of switching IDEs like from CLion to VS Code, if all else is equal. But all else is rarely equal, and the real-world answer lies in configuration, integrations, and defaults, not the IDEs themselves.

Here’s a breakdown of the likely causes:

1. VS Code Debugger Launch Configuration (Slow GDB Start-Up)

VS Code uses the launch.json configuration to run/debug your code. If it’s misconfigured, you may get slow startup or performance degradation during debugging.

Culprit examples:

  • externalConsole: false (can cause weird I/O bottlenecks)
  • logging or "trace": true (turns on verbose output)
  • Overhead from the cppdbg or cppvsdbg extension debugger

Fix:

  • In .vscode/launch.json, minimize unnecessary features:
"configurations": [
  {
    "name": "Debug",
    "type": "cppdbg",
    "request": "launch",
    "program": "${workspaceFolder}/your_binary",
    "args": [],
    "stopAtEntry": false,
    "cwd": "${workspaceFolder}",
    "environment": [],
    "externalConsole": true,         // Often faster than integrated
    "MIMode": "gdb",
    "setupCommands": [
      {
        "description": "Enable pretty-printing",
        "text": "-enable-pretty-printing",
        "ignoreFailures": true
      }
    ]
  }
]

2. Compiler/Build System Integration

CLion has a tight CMake integration and uses its own Ninja backend and optimized compiler toolchain invocation. VS Code’s CMake Tools extension is more flexible, but often misconfigured or uses slower defaults.

Fix:

  • If you use CMake in VS Code, make sure you’re:
    • Using Ninja or a Makefiles generator instead of the slow default
    • Setting up Release or RelWithDebInfo when appropriate
    • Running with the same compiler and flags as CLion

Check .vscode/settings.json:

{
  "cmake.generator": "Ninja",
  "cmake.buildDirectory": "${workspaceFolder}/build",
  "cmake.configureArgs": ["-DCMAKE_BUILD_TYPE=Debug"],
  "cmake.sourceDirectory": "${workspaceFolder}"
}

3. GDB Performance Overhead

GDB can be slow when:

  • Debugging code with heavy symbols (-g3 + no optimization)
  • Debugging optimized builds (-O2 or -O3) without -g can also confuse it
  • It’s stepping through STL-heavy code

CLion ships with bundled settings that improve GDB’s performance, such as:

  • Pretty printers
  • Smart path mapping
  • Proper gdbinit setup

Fix:

Use the same gdb binary in both IDEs and check if you’re:

  • Using gdb -ex "set debuginfod enabled off" (sometimes improves startup)
  • Running with or without pretty-printing (which affects performance)

4. VS Code Extension Overhead

The VS Code C++ extension (ms-vscode.cpptools) sometimes introduces overhead — especially with IntelliSense mode, background indexers, and slower DAP integration.

Fix:

Disable unused features:

{
  "C_Cpp.intelliSenseEngine": "Disabled",
  "C_Cpp.autocomplete": "Disabled",
  "C_Cpp.errorSquiggles": "Disabled"
}

Or switch to using lldb or minimal GDB where applicable.

5. Background Processes / Disk I/O

CLion’s CMake backend is often more efficient with caching and parallel builds than Makefiles in VS Code. Also, your terminal/console output (TTY redirection) might be slower in the integrated terminal of VS Code vs. CLion’s more optimized terminal.

Summary: Why VS Code Can Feel Slower

Cause CLion Advantage VS Code Disadvantage
Debug config defaults Smart gdb/lldb setup Slower cppdbg or wrong launch.json
Build system integration Tightly optimized CMake + Ninja Often misconfigured or using slow make
Terminal performance Uses fast I/O/PTY handling Slower integrated console in some setups
Symbol and STL handling in GDB Custom tuned settings Might lack tuning (e.g., pretty-printers)
Indexing/analysis Native code model CppTools extension can lag or reindex

Recommended Steps

  1. Ensure your VS Code uses Ninja + same build type (Debug/Release) as CLion.
  2. Disable or fine-tune IntelliSense, debugger logging, and external console use.
  3. Run GDB with minimized flags; compare gdb versions between systems.
  4. Benchmark with a minimal main() to isolate if it’s debugger, compiler, or terminal causing the delay.

Let me know your launch.json and tasks.json setup if you want a quick audit.