Module rustc_wrapper 

RUSTC_WRAPPER shim that restores absolute paths in SBF DWARF output.

Problem

The Solana toolchain’s cargo passes -Zremap-cwd-prefix= (empty replacement) to rustc for every SBF crate. This strips DW_AT_comp_dir from the DWARF, making all source paths relative. When multiple crates share filenames like src/lib.rs, the debugger can’t tell them apart and may show source from the wrong crate.

Solution

anchor debugger sets RUSTC_WRAPPER to the anchor binary itself. Cargo then invokes anchor <real-rustc> <args...> for every rustc call. This module detects that invocation pattern (the env var __ANCHOR_RUSTC_WRAPPER=1 disambiguates from normal CLI usage) and replaces -Zremap-cwd-prefix= with -Zremap-cwd-prefix=$CWD, preserving absolute paths in the debug info.

The sentinel env var is necessary because RUSTC_WRAPPER mode passes a path as argv[1] (the real rustc binary), which clap would reject as an unknown subcommand. The check in main.rs runs before clap parsing so the process never hits the normal CLI dispatch.

Performance

The wrapper adds ~1ms of fork+exec overhead per rustc invocation. This is negligible compared to actual compilation time.

Constants

WRAPPER_SENTINEL

Env var set by anchor debugger before calling cargo build-sbf. When present, the process knows it was invoked as a RUSTC_WRAPPER and should rewrite args instead of running the normal CLI.

Functions

maybe_exec_as_wrapper

If we’re running as a RUSTC_WRAPPER (sentinel env var is set), rewrite the rustc args and exec the real compiler. Never returns.