Stack overflow during shader compilation

Expected Behaviour

Here is an issue I just faced when replacing a loop with two direct calls:

error: failed to run custom build command for `ab-proof-of-space-gpu v0.1.0 (/web/github/abundance/crates/farmer/ab-proof-of-space-gpu)`

Caused by:
  process didn't exit successfully: `/home/nazar-pc/.cache/cargo/target/debug/build/ab-proof-of-space-gpu-62f09b5708f23384/build-script-build` (exit status: 1)
  --- stdout
  cargo:rerun-if-env-changed=RUSTGPU_CODEGEN_ARGS
  cargo:rerun-if-env-changed=RUSTGPU_RUSTFLAGS
  cargo:rerun-if-env-changed=RUSTGPU_CARGOFLAGS

  --- stderr
     Compiling ab-proof-of-space-gpu v0.1.0 (/web/github/abundance/crates/farmer/ab-proof-of-space-gpu)
  error: rustc interrupted by SIGSEGV, printing backtrace

  /home/nazar-pc/.rustup/toolchains/nightly-2025-06-30-x86_64-unknown-linux-gnu/lib/librustc_driver-d3e8ca52c6974f9d.so(+0x3ba5b2f)[0x7fe0de5a5b2f]
  /lib/x86_64-linux-gnu/libc.so.6(+0x45330)[0x7fe0da645330]
  /home/nazar-pc/.cache/rust-gpu/codegen/https___github_com_Rust-GPU_rust-gpu+6a9ea3bb/librustc_codegen_spirv.so(+0x104223f)[0x7fe0ce04223f]

  ### cycle encountered after 3 frames with period 6
  /home/nazar-pc/.cache/rust-gpu/codegen/https___github_com_Rust-GPU_rust-gpu+6a9ea3bb/librustc_codegen_spirv.so(+0xff3f85)[0x7fe0cdff3f85]
  /home/nazar-pc/.cache/rust-gpu/codegen/https___github_com_Rust-GPU_rust-gpu+6a9ea3bb/librustc_codegen_spirv.so(+0x100f353)[0x7fe0ce00f353]
  /home/nazar-pc/.cache/rust-gpu/codegen/https___github_com_Rust-GPU_rust-gpu+6a9ea3bb/librustc_codegen_spirv.so(+0x10424c9)[0x7fe0ce0424c9]
  /home/nazar-pc/.cache/rust-gpu/codegen/https___github_com_Rust-GPU_rust-gpu+6a9ea3bb/librustc_codegen_spirv.so(+0xff3f85)[0x7fe0cdff3f85]
  /home/nazar-pc/.cache/rust-gpu/codegen/https___github_com_Rust-GPU_rust-gpu+6a9ea3bb/librustc_codegen_spirv.so(+0x100f353)[0x7fe0ce00f353]
  /home/nazar-pc/.cache/rust-gpu/codegen/https___github_com_Rust-GPU_rust-gpu+6a9ea3bb/librustc_codegen_spirv.so(+0x10424c9)[0x7fe0ce0424c9]
  ### recursed 42 times

  /home/nazar-pc/.cache/rust-gpu/codegen/https___github_com_Rust-GPU_rust-gpu+6a9ea3bb/librustc_codegen_spirv.so(+0xff3f85)[0x7fe0cdff3f85]

  note: rustc unexpectedly overflowed its stack! this is a bug
  note: maximum backtrace depth reached, frames may have been lost
  note: we would appreciate a report at https://github.com/rust-lang/rust
  help: you can increase rustc's stack size by setting RUST_MIN_STACK=16777216
  error: could not compile `ab-proof-of-space-gpu` (lib)

  Caused by:
    process didn't exit successfully: `/home/nazar-pc/.rustup/toolchains/nightly-2025-06-30-x86_64-unknown-linux-gnu/bin/rustc --crate-name ab_proof_of_space_gpu --edition=2024 crates/farmer/ab-proof-of-space-gpu/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --crate-type dylib --crate-type lib --emit=dep-info,link -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2 --warn=rust_2018_idioms --warn=missing_debug_implementations --allow=unexpected_cfgs --check-cfg 'cfg(target_arch, values("spirv"))' --check-cfg 'cfg(docsrs,test)' --check-cfg 'cfg(feature, values())' -C metadata=420c5aaec24189dd --out-dir /home/nazar-pc/.cache/cargo/target/debug/build/ab-proof-of-space-gpu-fecff1fdb1528c5b/out/spirv-unknown-vulkan1.2/debug/deps --target /home/nazar-pc/.cache/rust-gpu/codegen/https___github_com_Rust-GPU_rust-gpu+6a9ea3bb/target-specs/spirv-unknown-vulkan1.2.json -C incremental=/home/nazar-pc/.cache/cargo/target/debug/build/ab-proof-of-space-gpu-fecff1fdb1528c5b/out/spirv-unknown-vulkan1.2/debug/incremental -L dependency=/home/nazar-pc/.cache/cargo/target/debug/build/ab-proof-of-space-gpu-fecff1fdb1528c5b/out/spirv-unknown-vulkan1.2/debug/deps -L dependency=/home/nazar-pc/.cache/cargo/target/debug/build/ab-proof-of-space-gpu-fecff1fdb1528c5b/out/debug/deps --extern ab_blake3=/home/nazar-pc/.cache/cargo/target/debug/build/ab-proof-of-space-gpu-fecff1fdb1528c5b/out/spirv-unknown-vulkan1.2/debug/deps/libab_blake3-a4e221411a36f2cf.rlib --extern ab_chacha8=/home/nazar-pc/.cache/cargo/target/debug/build/ab-proof-of-space-gpu-fecff1fdb1528c5b/out/spirv-unknown-vulkan1.2/debug/deps/libab_chacha8-13720534e6d2d2e7.rlib --extern 'noprelude:compiler_builtins=/home/nazar-pc/.cache/cargo/target/debug/build/ab-proof-of-space-gpu-fecff1fdb1528c5b/out/spirv-unknown-vulkan1.2/debug/deps/libcompiler_builtins-372bb16695370e45.rlib' --extern 'noprelude:core=/home/nazar-pc/.cache/cargo/target/debug/build/ab-proof-of-space-gpu-fecff1fdb1528c5b/out/spirv-unknown-vulkan1.2/debug/deps/libcore-876111756530f1ee.rlib' --extern derive_more=/home/nazar-pc/.cache/cargo/target/debug/build/ab-proof-of-space-gpu-fecff1fdb1528c5b/out/spirv-unknown-vulkan1.2/debug/deps/libderive_more-76a08933c84dae4d.rlib --extern spirv_std=/home/nazar-pc/.cache/cargo/target/debug/build/ab-proof-of-space-gpu-fecff1fdb1528c5b/out/spirv-unknown-vulkan1.2/debug/deps/libspirv_std-d8b5ef86ea70b0dd.rlib -Z unstable-options -Zcodegen-backend=/home/nazar-pc/.cache/rust-gpu/codegen/https___github_com_Rust-GPU_rust-gpu+6a9ea3bb/librustc_codegen_spirv.so -Zbinary-dep-depinfo -Csymbol-mangling-version=v0 '-Zcrate-attr=feature(register_tool)' '-Zcrate-attr=register_tool(rust_gpu)' -Coverflow-checks=off -Cdebug-assertions=off -Zinline-mir=off -Zmir-enable-passes=-GVN -Zshare-generics=off -Cllvm-args=--spirv-metadata=name-variables -Ctarget-feature=+GroupNonUniformArithmetic,+GroupNonUniformBallot,+GroupNonUniformShuffle` (signal: 11, SIGSEGV: invalid memory reference)

Looks like recursion that went too deep somewhere.

RUST_MIN_STACK=16777216 suggestion did help, so it is not an infinite loop or anything like that, just uses too much stack space due to recursion.

Example & Steps To Reproduce

Remove this line: https://github.com/nazar-pc/abundance/blob/1639a5172a9792d4989a4615de264f23106752be/crates/farmer/ab-proof-of-space-gpu/build.rs#L38

Then:

cd crates/farmer/ab-proof-of-space-gpu
cargo build

System Info

Rust-gpu from 6a9ea3bb96d34b2d5211a34d09fae81b0c938916 and cargo-gpu from https://github.com/Rust-GPU/cargo-gpu/commit/09829681cbe3866b6d1fc2ee0eae83aa77855b3e

Start with crates/farmer/ab-proof-of-space-gpu/build.rs at the referenced line and reproduce with cd crates/farmer/ab-proof-of-space-gpu && cargo build after removing it. Inspect the rust-gpu codegen recursion shown in the backtrace and compare behavior with RUST_MIN_STACK set. Done means the direct-call version compiles without requiring the larger stack workaround.