cpptools-srv.exe causes system memory to reach 99% when opening newly created C++ files

[lmoonzs]

Type: Bug

Description

When using the Microsoft C/C++ extension, opening newly created .cpp files in my C++ project causes cpptools-srv.exe to rapidly consume system memory.

On a machine with 32 GB RAM, system memory quickly reaches 99%, causing the whole system to become extremely slow or nearly unresponsive.

After uninstalling the Microsoft C/C++ extension, the issue disappears. Opening and switching between the same newly created .cpp files no longer causes the memory spike.

This strongly suggests that the issue is caused by cpptools-srv.exe / the C/C++ extension's IntelliSense or parsing behavior.

Steps to Reproduce

1. Install Microsoft C/C++ extension ms-vscode.cpptools.
2. Open a C++ project in VS Code.
3. Create a new .cpp file in the project.
4. Open the newly created .cpp file.
5. Switch between this new .cpp file and another .cpp file.
6. Observe Windows Task Manager.

Expected Result

Opening or switching between C++ files should not cause excessive memory usage. VS Code and the system should remain responsive.

Actual Result

cpptools-srv.exe rapidly increases memory usage. System memory reaches 99% on a 32 GB RAM machine. The system becomes extremely slow or nearly unresponsive.

In one occurrence, my wireless mouse stopped responding until I unplugged and replugged the USB receiver into another USB port. Codex also crashed afterwards with the following error, likely because the system was out of memory:

(code=3221226505, signal=null)
Most recent error: memory allocation of 225072 bytes failed
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Extension version: 1.32.2
VS Code version: Code 1.119.0 (8b640eef5a6c6089c029249d48efa5c99adf7d51, 2026-05-05T11:23:50-07:00)
OS version: Windows_NT x64 10.0.26200
Modes:

<details>
<summary>System Info</summary>

|Item|Value|
|---|---|
|CPUs|AMD Ryzen 7 7840HS w/ Radeon 780M Graphics      (16 x 3793)|
|GPU Status|2d_canvas: enabled<br>GPU0: VENDOR= 0x1002, DEVICE=0x15bf [AMD Radeon 780M Graphics], DRIVER_VENDOR=AMD, DRIVER_VERSION=32.0.31007.1017 *ACTIVE*<br>GPU1: VENDOR= 0x1414, DEVICE=0x008c [Microsoft Basic Render Driver], DRIVER_VERSION=10.0.26100.8328<br>Machine model name: <br>Machine model version: <br>direct_rendering_display_compositor: disabled_off_ok<br>gpu_compositing: enabled<br>multiple_raster_threads: enabled_on<br>opengl: enabled_on<br>rasterization: enabled<br>raw_draw: disabled_off_ok<br>skia_graphite: disabled_off<br>trees_in_viz: disabled_off<br>video_decode: enabled<br>video_encode: enabled<br>webgl: enabled<br>webgl2: enabled<br>webgpu: enabled<br>webnn: disabled_off|
|Load (avg)|undefined|
|Memory (System)|31.22GB (20.76GB free)|
|Process Argv|D:\\CGMB --crash-reporter-id e779c159-232b-42af-9584-e297d63d4cb0|
|Screen Reader|no|
|VM|0%|
</details><details>
<summary>A/B Experiments</summary>

vsliv368cf:30146710
binariesv615:30325510
nativeloc1:31344060
dwcopilot:31170013
dwoutputs:31242946
copilot_t_ci:31333650
e5gg6876:31282496
pythonrdcb7:31342333
6518g693:31463988
aj953862:31281341
6abeh943:31336334
envsactivate1:31505457
cloudbuttont:31379625
3efgi100_wstrepl:31403338
ec5jj548:31422691
cp_cls_c_966_ss:31454199
inlinechat_v2_hd992725:31505030
4je02754:31466945
8hhj4413:31478653
cp_cls_c_1081:31454833
conptydll_true:31498968
e9c30283:31461165
test_treatment2:31471001
46204921:31447328
idci7584:31464702
e3e4d672:31494082
ei9d7968:31496641
chat:31457767
7e187181:31503455
ghj88844:31499326
ec1eg703:31491645
ddid_t:31478206
1b2f8594:31509479
getcmakediagnosticsoff:31489825
7df3h592:31512476
cp_cls_c_1082:31504161
logging_enabled_new:31498466
db5d2638:31499441
jb_cp_cls_c_632:31510883
852d2892:31506239
748c7209:31512887
j7be3939_tst_off:31511780
32d76977:31512328
ha629193:31508444
539gd155_c:31506875
e6ac6c27:31509471

</details>

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[sean-mcmanus]

@lmoonzs What are the contents of the C++ file? Your repro info sounds like you expect it to always repro, but we have not seen any other reports of this.