g++/clang "internal compiler error: Killed" (OOM)

By Kaveh Alemi·Latchkey

An "internal compiler error: Killed" with (program cc1plus) is almost never a compiler bug. The OOM killer terminated the compiler because a single translation unit (or many parallel ones) exceeded the runner RAM.

What this error means

A C/C++ build fails with internal compiler error: Killed (program cc1plus) or cc1. Lowering -j or using a larger runner clears it with no source change.

shell

g++: internal compiler error: Killed (program cc1plus)
Please submit a full bug report...
make[1]: *** [foo.o] Error 4

Common causes

Too many parallel compiler processes

A high -j value runs many cc1plus instances at once; combined memory use exceeds the runner and the OOM killer fires.

One heavy translation unit

Template-heavy or generated source can make a single compile spike past available RAM.

How to fix it

Lower compile parallelism

Fewer parallel jobs cuts peak memory dramatically.

shell

make -j2          # instead of -j$(nproc)
# or for cmake/ninja
cmake --build . -j 2

Add memory or reduce per-unit cost

Run the build on a runner with more RAM.
Split or simplify the heaviest translation units.
Use precompiled headers to cut per-file memory.

How to prevent it

Tune -j to the runner RAM, not just cores.
Right-size memory for C++ builds.
Watch peak memory during compiles.

Frequently asked questions

What causes "ICE: Killed (OOM)"?

A high -j value runs many cc1plus instances at once; combined memory use exceeds the runner and the OOM killer fires.

How do I fix ICE: Killed (OOM)?